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How to: Replace the rusty trunk lid stay-damper-bracket bolts
Evo X How Tos / InstallationsPost or link to your detailed how to / installation articles in here. If you have any questions regarding the how tos, feel free to post them in the Request sub-forum.
How to: Replace the trunk lid damper bracket (and other rusty) bolts
Summary
This is a very straight-forward job. The hardest step is sourcing the corrosion-resistant M6x16 bolts. Once you have them, un-screw one rusty bolt, screw in your new bolt with a split spring washer and a flat washer, use your torque wrench and torque it to 43 in-lbs (4.9 N·m). Continue to replace the other 3 bolts one by one, and you are done.
Background
Mitsubishi's Mizushima assembly line used very cheap, interior-only M6x17(?) steel bolts with washers to install the stay damper brackets on the trunk lid. They are not corrosion-resistant and should not be used as body components. Rain and salt cause these bolts and washers to rust quickly. It's wise to replace them before the rust starts spreading.
Sourcing the hardware
I asked my friend who works at a car dealership. He recommended me a specialty hardware store that supplies the dealers with bolts, nuts, and hard-to-find automotive fasteners. It's a pleasant surprise that the store has 316 marine steel hardware, which is ideal for this job. What you need:
▪ 4x M6x16 (or M6x17) hex bolts, marine-grade 316 stainless steel
▪ 4x M6 split spring washers, marine-grade 316 SS
▪ 4x M6 flat washers, marine-grade 316 SS
Alternatively, if you like titanium hardware for the bling, keep in mind that titanium acts like a cathode and will have a galvanic corrosion effect on the steel trunk lid. Use an anti-seize formulated for dissimilar metals to reduce the corrosion.
The damper brackets are a structural component and have to resist shear stress from the vehicle body flex. So it may not be a good idea to use nylon, plastic, or aluminum hardware.
If the marine-grade hardware is too difficult to source, you may want to use the most corrosion-resistant hardware available to you.
I found a 40-200 in-lbs torque wrench at the Crappy Tire which is perfect. The big ones for wheel lug nuts might not allow you to set the torque as low as 43 in-lbs (3.6 ft-lbs).
Extracting rusty bolts
Be extremely gentle when extracting the rusty bolts! There is some sort of a square weld nut behind the sheet metal. But do not assume it's sufficiently strong. If the weld nut breaks off, you will have a bad day. Extract slowly, use penetrating oil if needed, and keep the bolt straight to minimize the stress on the weld nut behind.
Installing new bolts
I measured the stock bolts' installation torque by marking them with a bronze marker, loosening them, and then re-tightening them to the original angle. They are around 41.5~43 in-lbs (approx 4.8 N·m) from the Mizushima factory. Meanwhile, the Service Manual (Group 42A Body) recommends 44 in-lbs (5.0 N·m) for these bolts. For my own Evo, I simply took an average and set my torque wrench at 43 in-lbs (4.9 N·m).
Maintain the bolt—split spring washer—flat washer design like the OEM, before installing and tightening each. These bolts did not have the bolt mark indicators from the factory. But if you are OCD like me, you can mark them. I found Sharpie Metallic Silver to be a very subtle marker for this.
You may be tempted to replace the equally rusty rear wing bolts. But realize that changing those bolts is a lot more involved. Watch some YT videos on Evo X's rear wing installation guides to have a general idea how the rear wing is attached to the trunk lid. You may need a body shop to take off the rear wing, have everything cleaned, and re-install the wing with fresh bolts professionally.
Before (left) and after (right).
Last edited by Lightsaber; Apr 3, 2024 at 12:30 AM.
Reason: typo
How to: Replace rusty ECU bracket and relay box bolts
Instead of thread-whoring and posting a bunch in the Evo X How-To forum, I think it's better to write additional fastener replacement guides as posts here.
Building on the initial success, I went back to the fastener shop and bought a box full of additional Evo-sized Tong Hwei Enterprise (THE) A2-70 and A4-70 stainless steel hardware. I'm very pleased with the top-quality THE bolts made in Kaohsiung, Taiwan, as they are much better than the typical cheap bolts from a certain neighboring country. With them, I can try to replace more rusted bolts on my car:
Big relay box bolts
▪ Factory: Misumi(?) M6x16 Class 4.8(?) hex bolt + split spring washer + flat washer.
▪ Factory torque measured: 42 in-lbs (4.8 N·m).
▪ Service manual torque: 44(?) in-lbs (5.0[?] N·m).
▪ Replacement: THE M6x16 Class A4-70 hex bolt + split spring washer + flat washer.
▪ Torque I used: 43 in-lbs (4.9 N·m).
These bolts are very rusty and I had to watch a few YT videos on how to extract rusted bolts. I used some 3-in-One® penetrating oil, put a 10mm socket with an extension rod on it, and hammered the rod tip very gently with the back end of the hammer every 15 minutes. The more rusty rear one started to loosen as I turn my wrench after 3 hammering tries.
It's interesting that most Evo X engine bay dress-up bolt kits include only the front relay box bolt, but not the rear one.
ECU bracket bolts
▪ Factory: Misumi(?) M6x16 Class 4.8(?) hex bolt + split spring washer + flat washer.
▪ Factory torque measured: 53 in-lbs (6.0 N·m).
▪ Service manual torque: ?
▪ Replacement: THE M6x16 Class A4-70 hex bolt + split spring washer + flat washer.
▪ Torque I used: 53 in-lbs (6.0 N·m).
These bolts are a pleasant breeze to replace. Just have your hands steady like a neurosurgeon, and do not drop your own washer into the engine bay. Else it would be a nightmare to get the washer out.
The vertical bracket has more bolts, which might require unplugging and taking out the ECU if you want to replace them.
Air box and other bolts that I did not replace
The air box bolt, while M6, has embedded washers: a split spring one and a 25(?)-mm fender washer. I think it would be unwise to replace it with a non-OEM one. If the washers are not embedded, they can be accidentally dropped into the engine bay when servicing something that requires taking out the air box.
The little fuse box bolt is a specialty bolt, installed with a massive amount of torque. If it becomes rusty, I would prefer only an OEM replacement. There are rumors that early model Evo X's have a mild steel bolt at this place, which might be why the Service Manual (page 11A-77) recommends absurdly low 36 in-lbs (4.0 N·m) of torque.
My fender bolts with the fender washers are installed by a body shop. There are measured around 40 in-lbs (45 N·m). My headlight housing bolts are measured around 32~38 in-lbs (3.6~4.3 N·m). The body shop installed it at the low end, while the factory installed it at the high end.
ECU-side bolts.
For these bolts, I have been tightening them dry to the specified torque, just like people said on the Garage Journal forum:
Originally Posted by lawfarm
Any time a torque spec is provided by the manufacturer, that spec is a 'dry' spec, unless it expressly indicates that it is a wet (lubed) spec. If it is a wet spec, it will indicate what kind of lube is appropriate.
As noted above, dry bolts will reach a specified torque faster than lubed bolts, with all else being equal. That is correct, and is what the manufacturer intends. Bolts/nuts/studs with specified torque figures are generally intended to be assembled dry.
In the example noted above, with wheels on a concrete truck, the torque figure spec'd for the wheels is almost certainly a 'dry' spec. By oiling the threads, you are almost undoubtedly overtightening the bolts, beyond the designed torque spec, unless you are reducing the torque by the appropriate percentage based on the lube being used. If wheels are coming loose at the design torque spec (without lube), that either means that the spec is wrong, or the wheels aren't being torqued to the spec, or the wheels are being torqued improperly (not in the right sequence, etc.). Adding lube means that you're just tightening them more than intended, which can lead to stud/bolt stretch or failure.
I'm aware that some master mechanics torque the bolts with anti-seize. I heard rumors that even the AMS master techs back in the good ol' days did so when working on the Evo's, to maintain excellent reliability and serviceability. However, I'm still a rookie myself, and am not familiar yet with calculating a wet spec torque from a dry spec. I might try some anti-seize in the future though:
Originally Posted by pstnbly
I agree with Moose and Kmkalf, in nearly 40 years of wrenching in the no.east neversieze is a savior. I use it on sparkplugs ,wheels, and most undercarriage parts. I work on everything from weedwackers to $350,000 Pistenbully's ( glorified bulldozers) and my track record proves my techniques, I break less fasteners and my fitments stay together better than my peers by a large margin. No light oil on torqued fasteners? the fastener better be spotlessly new, even factory new fasteners have a light coating. Another thing I do is after cleaning battery terminals is coat them in and out with lithium complex grease, a little messy but my batteries last easily twice as long and rarely need servicing, dielectric grease in connectors also.
In addition, I found a Fastenal guide that asks to "assemble with a slow and continuously applied torque". The technic really helps to get some bolts into the not-so-smooth threads without damaging anything:
Speaking of the class (grade) of bolts, I found a comparison chart by Allied Fastenings that's very helpful on this topic:
Allied Fastenings -> Technical Data -> Compare Tensile Strength of Steel Grades and Classes.
Metric class of the bolts
Therefore, here is what I think:
▪ Mild steel: We should be able to replace it with A2-70 stainless steel, or A4-70 marine steel.
▪ Class 8.8: These are the typical yellow zine-plated bolts and nuts. Stay with genuine OEM if it's still stock. Else replace with the same Class 8.8.
▪ Class 10.9: If it's engine-related, then either ARP or genuine OEM. Most aftermarket hardware do not measure up.
The WhichCar? magazine also has an article explaining the fasteners on cars. I find it educational:
Guide to fasteners for automotive applications DIY Modified car builders will deal with three basic grades of carbon-steel bolts and screws in building the car of their dreams
23 OCT 2019
For safety and reliability, it’s important to choose the proper grade and the correct installation to ensure you’re safe in your machine.
The main grades of steel bolts and screws in both imperial and metric are shown in Table 1 (see below).
BUCKET OF BOLTS
Mild-steel bolts (also called Grade 2 or metric 5.8) have a proof strength of about 385MPa. Proof strength is the stress that the fastener will withstand without any permanent set (irreversible damage). Grade 5 bolts have a proof strength of 600MPa, and Grade 8 has 840MPa. So the better the grade of the bolt, the more load it will withstand while still remaining elastic. When the load is released, a high-grade bolt returns to its original length and remains elastic, whereas a lower-grade one may go plastic and be permanently extended.
Most engineers use a factor of 60 per cent for the strength of a bolt in shear, so this is a useful rule for you to use in selecting the right size and grade for shear applications. I think it’s fair to say that most modified vehicles are overdesigned in terms of fastener sizes, and in most cases it errs on the side of safety, but in some it can make things look truck-like. Smaller fasteners can make a vehicle look sharper, but, as one of my lecturers once said, if tractors were built on the limit of engineering no farmer would buy one because it would look too weak. In modern cars, however, we are now seeing the use of much smaller fasteners – so you decide! Many modifiers use socket-head fasteners, and these are all Grade 8 quality.
After selecting the right size of fastener, the selection of the grade should be based on the balance between tensile strength, ductility and toughness. Tensile strength is the ultimate strength of the material used in the fastener. Ductility is the amount the fastener will stretch before it fails. Toughness is about fatigue resistance and the ability to withstand cyclic stresses.
So understanding these facts about physical metallurgy, it becomes easier to select the correct grade of bolt.
For a seatbelt bolt, we want a ductile fastener that stretches a lot before failure, by which time the stress of a collision is over and the passenger is saved. For that reason, seatbelt fasteners are a mild grade and should not be replaced with high-tensile bolts, which reach their peak stress and fail suddenly. Similarly, Grade 2 or ungraded fasteners can also be used for mudguards, running boards, firewall fixings and other non-critical applications where stresses are low.
I think that Grade 5 (metric 8.8) fasteners are suitable for almost anything else on a modified vehicle. They have the tensile strength without the brittleness of a Grade 8 bolt. In suspensions they will resist the cyclic loads, and in other applications they will give shear and clamping strength without coming loose from ductility or overtightening.
For critical engine situations such as cylinder-head bolts and differential gearsets, the Grade 8 bolt is the way to go, where proper torqueing preloads the clamped joint with minimal bolt stretch.
GO NUTS
Nuts are generally made from low-carbon or mild steel, similar to a Grade 2 bolt. This may sound strange, but the length and thread design of nuts are determined so that bolts can achieve full strength under load. It means that if you over-torque a fastener you often strip the nut first, leaving the bolt intact.
When you torque a fastener to a specification, you are applying a preload that resists a load in the opposite direction, and also stresses the fastener to a point where additional load will not stretch the fastener and cause it to loosen.
Proper torqueing of all fasteners on a vehicle is important, but in less critical areas it is achieved using experience and conventional spanners. A spanner is designed for a specific fastener size; the bigger the fastener, the longer the spanner, in order to provide correct torque from the strength of a ‘standard’ person. You’ll all remember that the apprentice always breaks the quarter-inch screws until he or she learns that they must ease up on the smaller ones.
Nyloc nuts are very common on street-car projects and have pretty much replaced the old-faithful spring washer. They perform particularly well in applications where vibration or rotation is a factor, or where access is difficult for maintenance inspection. Ensure that there is at least one thread protruding through the nut for proper engagement. Do not use nylocs where heat will melt the nylon retaining material, and don’t overuse them once they have been undone more than twice.
TIPS
• Locate fasteners so that if the nut does come undone, the bolt or screw remains in place and can still do part of its job of location. Therefore, put the heads up or facing forward.
• Use correctly sized washers to suit the fastener shank. Clearance of 0.5 to 1mm is normal. Oversized washers can cause problems with location of clamped components.
• Make sure that you fit spacer tubes or bosses inside hollow items that are being clamped by a fastener, to avoid distortion of the hollow member during torqueing or under operational stress resulting in a loose fastener.
• Think about the thickness of material that fasteners bear up against in a bracket or item you are designing, so that the bolt does not overstress the parent material causing a slot that introduces poor performance and looseness to that joint.
• Similarly, ensure that holes you drill are not oversized for the fastener being used, or looseness, rattling and slotting will result. For fasteners under 6mm, a rule of thumb is 0.5mm clearance, and for 6-16mm, use 1mm as the clearance hole size. I can’t think of any fasteners bigger than 16mm needed on a street car.
• Stainless fasteners are great for their appearance on body components, but make sure that you order high-strength bolts from a good supplier for suspension, engine manifolds and higher-load applications.
Tim Bartrop
JOURNALIST Street Machine Archives
PHOTOGRAPHY
Last edited by Lightsaber; May 18, 2023 at 07:40 AM.
Reason: updated Fastenal chart
Ideally I would replace them with M8x17 stainless steel bolts with flat washers, because the washer can be approximately 1mm thick. However, I couldn't find M8x17 bolts, so I'm replacing them with M8x16 bolts. They stick out just a tad from the bottom of the weld nuts, as the factory engineer intends. So I believe these M8x16 bolts are sufficient in their length.
I torqued them in 2 stages to even the load. I first replaced the rusted OEM M8 bolts one by one, while torqueing my THE M8x16 bolts to 60 in-lbs (6.8 N·m). I then re-torqued these 2 bolts to 100 n-lbs (11.3 N·m). I checked them after a week of driving, and they remain tight.
A/C return line bolt
This is an easy piece of cake. Just hold it really steady and avoid dropping anything into the engine bay.
▪ Factory: Misumi(?) M6x16 Class 4.8(?) hex bolt + split spring washer + flat washer.
▪ Factory torque measured: 50 in-lbs (5.6 N·m).
▪ Service manual torque: ?
▪ Replacement: THE M6x16 Class A4-70 hex bolt + split spring washer + flat washer.
▪ Torque I used: 50 in-lbs (5.6 N·m).
Engine mount ground wire bolt
Even though this is just a regular Class 4 bolt and not an electric bronze bolt, you should think twice before replacing this one. The location is tedious. If you cannot be 100% certain that you won't drop anything close to the multi-V belt, leave this bolt alone. If the bolt is really rusty, you can bring your replacement M6x16 bolt and washers to a professional mechanic next time you need an oil change.
▪ Factory: Misumi(?) M6x16 Class 4.8(?) hex bolt + split spring washer + flat washer.
▪ Factory torque measured: 48 in-lbs (5.4 N·m).
▪ Service manual torque: ?
▪ Replacement: THE M6x16 Class A4-70 hex bolt + split spring washer + flat washer.
▪ Torque I used: 49 in-lbs (5.5 N·m).
Metric Bolts and Numbers
When shopping for replacement bolts, I found a post on AdvRider that's very helpful:
Originally Posted by Yossarian™
The marks approximately correspond to the following property classes:
Head Mark "4": 4.6, 4.8, 5.6, 5.8, 6.8
Head Mark "7": 8.8
Head Mark "8": 9.8
Split spring washer controversy
Most North American mechanics don't like split spring washers, because using a Junker test machine, it shows that they cause the bolt to loosen faster than with just a flat washer. Mitsubishi engineers, however, like the split spring washers and you can find them everywhere in our Evo X. I was debating whether to use a single flat washer, double Belleville washers (facing each other like a clam shell), or a split spring washer plus a flat washer just like the OEM. Eventually I went with the OEM, because with a flat washer, once a bolt pops loose, it loses 100% of its clamp load. But with a split spring washer, even if the bolt vibrates loose, it still retains a small portion of its clamp load, thus improving reliability.
NMech has an article explaining this. From my experience, what he said is true. Using only a flat washer, the torque wrench clicks at that exact angle every single time. With a split spring washer (a.k.a lock washer), the angle become muddier and much more forgiving. Even if the bolt is not perfectly tightened, the clamp load is still there:
Originally Posted by NMech
There are subtle differences. Its definitely not wrong. IMHO, its a matter of priorities. The lock washer usually improves the behavior of the bolt from coming undone. However, there are a lot of ifs and details that need to be considered.
1. components
First of all a short discussion about the individual components (lock washer and plain washer).
1.1 plain washer
In general, the plain washer helps by distributing the loads in a greater surface [...].
1.2 lock washer
The lock washer has two distinctive functions:
1. it digs into the surfaces that is in contact
2. it behaves as spring and it can maintain a minimum clamping force over a greater distance.
Especially the second one is very important (you should look into joint stiffness, because its hard to explain here), however the idea is that the lock washer behaves as a soft spring (relatively to the bolt). When you tighten a lock washer you can displace the lock washer for at least mm without significant increase in the force. If on the other hand you didn't use a washer, then the force for tightening would increase very fast upon contact of the bolt with the clamped material. The benefit is that if there is displacement induced vibration, there is almost always a residual force, that doesn't allow the bolt to rotate.
2. Configurations
Additionally there is a difference whether its a bolt-nut or just a fastener.
2.1 fastener Figure: blind fastener configuration
My preferred way when there is a blind fastener (sometimes called cap screw) clamping two pieces, is just using a lock washer. Only using a lock washer and tightening it sufficiently will probably create some sort of marking on the surface, which will inhibit further the untightening of the screw.
Using the plain washer, is helpful because it spreads the loads, however, if you are worried about dynamic loads, and untightening due to vibrations, the plain washer will probably won't help
2.2 bolt nut
When using a bolt nut, - in general- the preferred way (at least the one that I was told by experts), is that its best to have the plain washer at the bolt head, and the lock washer on the side of the nut.
By digging in the surface, the lock washer reduces the probability of the bolt rotating.
Bottom line
If the main worry is to
• secure the bolt, then just the lock washer is better (although there are better ways - castellated nuts and lock pins).
• to protect the clamped material (especially if the clamped material is soft see PLA), then I would prefer using the lock washer with the plain washer (clamped material - plain washer - lock washer - bolt/screw)
I guess the bottom line is that you need to consider the priorities on each application.
For bolts with unknown tightening torques, I find this Grampian guide helpful. However, be careful that these torques tend to be quite high. Mitsubishi Evo X's Service Manual 11B-20, for instance, recommends only 49 N·m (36 ft-lbs) for the head-to-manifold M10 nuts:
M10 bolt approx torque: Class 4.6 = 22 N·m (16 ft-lbs). Class 8.8 = 56.3 N·m (41.5 ft-lbs). Class 10.9 = 77 N·m (57 ft-lbs). Class 10.9 = 92 N·m (68 ft-lbs).
Last edited by Lightsaber; May 18, 2023 at 07:43 AM.
Reason: updated the Grampian chart
These are specialty bolts with 4 radial lines on their heads, probably Class 8.8 structural bolts with sacrificial zinc plating. Mine are so rusted that the mechanic recommends lowering the tightening torque to 60 in-lbs (6.8 N·m) to prevent them from breaking due to fatigue. As I shopped for new ones, the Mitsubishi dealer told me that the OEM replacements (p/n: MF911151) are back-ordered. So I bought the ARP ones (p/n: 760-1001). Tools needed:
ARP requires anti-seize for these Class 10.9 (Grade 8) super-strength stainless steel bolts. So I bought the MotoMaster nickel-based anti-seize from Crappy Tire. Usually, anti-seize would require lowering the torque by 10%~25%. However, using one ignition coil bolt, I have measured the torque needed to tighten the bolt to the same angle, and found that the MotoMaster nickel anti-seize to be a uniquely thick compound. It contributed to almost zero difference in the torque required. So I decided to lower the Service Manual torque by 10%, from 89 in-lbs (10.0 N·m) to 80 in-lbs (9.0 N·m):
▪ Factory: M6x1.00x20 smooth-flanged hex bolts, quantity: 4.
▪ Factory torque measured: unknown.
▪ OEM part number: MF911151, quantity: 4 (10mm socket).
▪ ARP part number: 760-1001, one set which includes 5 bolts (8mm socket).
▪ Service manual torque: 89 in-lbs (10.0 N·m).
▪ Torque I used: 80 in-lbs (9.0 N·m).
To apply a small amount of the anti-seize, I coated the lower 2/3 of each ARP bolt, and then patiently wiped it off with a microfiber towel. This way, the small amount of anti-seize remaining can protect the threads without making a mess.
The ARP 760-1001 comes with flat washers. It's okay to use them, because well-centered, the washers can spread out the clamping force over the entire metal sleeve on the ignition coils. It's also okay not to use them, because the bolts' heads are large enough to cover the sleeves anyway.
I replaced the ignition coil bolts one by one, gently tightening them to 80 in-lbs (9.0 N·m) and it's all set.
ARP 760-1001 installed as ignition coil bolts on Evo X.
Service Manual page 11B-10 recommends 89 in-lbs (10.0 N·m) for the ignition coil bolts.
Service Manual page 16-39 recommends 84 in-lbs (9.5 N·m) for the bolts.
Well, you definitely need a body shop for this. The factory did not apply any anti-rust treatment whatsoever on the steel brackets inside. In hindsight, if I knew it was this bad, I would instead dial up Bulletproof a year in advance for a Voltex wing.
Anyway, the body shop sandblasted the steel brackets, and sprayed primer and black paint. Hopefully this will slowdown the rust significantly. It took a specialist about 6 hours for everything. The body shop too prefers stainless steel hardware for a professional and long-lasting finish. I applied some anti-seize on the threads to prevent cold-welding.
Service manual 51-17 recommends massive 76 in-lbs (8.5 N·m) for the M6 bolts, so it seems that the engineer intended that Class 10.9 bolts would be used for this application. The Mizushima Plant however gives zero farcs and used mild steel bolts on 4 of the 6 holes. The body shop tried 33 in-lbs (3.7 N·m) typical for mild M6 bolts, but the rear wing would rattle on uneven roads. So I went back and asked them to increase the torque to 60 in-lbs (6.8 N·m), which is roughly the practical limit for A4-70 marine steel M6 bolts, and the rattling is gone entirely. Now, the Class 10.9 M6x16 bolts I bought just in case can chill in my toolbox.
Steel brackets inside the OEM rear wing after 9 years of daily driving.
The aluminum bar suffered minimal corrosion. But the steel brackets has rusted heavily.
The body shop sandblasted the steel brackets, and then sprayed primer.
Light rust started on the thread already, making me believe that a Voltex wing would be a better choice for the long term.
Black paint was spray painted over the primer.
Stock rear wing re-assembled. Note the light rust starting around the threaded holes from the weld nuts behind.
Rear wing re-installed using THE A4-70 and A2-70 hardware.
How to: Replace rusty fuel pump resistor bolts (power steering area)
Recently I got the chance to replace the Evo X's fuel pump resistor (MR481582) bracket bolts. They are mild steel bolts from the factory, and have become rusted. The M6 bolts require the 10mm hex socket. The M5 bolts require an 8mm hex socket. Apply light anti-seize evenly on the threads to prevent stainless steel from galling.
Fuel pump resistor bolts
▪ Factory: M5x10 hex bolt + split spring washer.
▪ Factory torque measured: 30 in-lbs (3.4 N·m).
▪ Service manual torque: ?
▪ Replacement: TD M5x10 Class A2-70 hex bolt + split spring washer.
▪ Torque I used: 30 in-lbs (3.4 N·m).
You need to take out the fuel pump resistor with its bracket in order to change these bolts. There is an inconspicuous tab at the far end of the female connector. Gently press it to unplug it. Both M5x9 and M5x10 bolts can work, but M5x12 or longer bolts will not thread all the way in and cause the resistor to rattle.
Fuel pump resistor bracket bolts
▪ Factory: Misumi(?) M6x16 Class 4.8(?) hex bolt + split spring washer + flat washer.
▪ Factory torque measured: 42 in-lbs (4.7 N·m).
▪ Service manual torque: 44(?) in-lbs (5.0[?] N·m).
▪ Replacement: THE M6x16 Class A4-70 hex bolt + split spring washer + flat washer.
▪ Torque I used: 42 in-lbs (4.7 N·m).
The brackets are brittle. Be sure to use a light-duty torque wrench, and do not over-tighten them.
Evo X fuel pump resistor (MR481582) bolts replaced with stainless steel ones.
The fuel pump resistor (MR481582) is made in Japan by Denso.
A brief discussion about stainless steel bolts and galling
Some people are strongly against stainless steel bolts because they gall easily:
Originally Posted by JackOfDiamonds
Stainless steel fasteners can gall so easily, you can have a quality bolt that is perfectly threaded into clean threads and if anything goes wrong it can instantly start galling to the point where it will be impossible to turn either way and you will have no choice but to snap it off.
From my limited experience, (1) using a high-quality anti-seize, (2) turning the bolt slowly and avoiding nyloc nuts on stainless steel bolts, and (3) choosing a properly strong stainless steel for the application have been effective in preventing galling. Stronger stainless steel usually (but not always) has a more durable layer of protective chromium oxide, which might be why that ARP and Bumax 88 stainless steel fasteners do not gall as easily. They still require anti-seize though.
Misumi has an article explaining how to prevent galling:
Originally Posted by Carlicia Layosa
Thread Galling Issues with Stainless Steel Fasteners 2 min read
One of the benefits of working with stainless steel is its resistance to corrosion. Unfortunately, some people experience issues with stainless steel fasteners and wonder why their fasteners are breaking or getting nicks like cheap screws from the dollar store. Why isn’t this robust metal holding up?
It’s actually the fact that stainless steel is built to avoid corrosion that makes it more susceptible to thread galling. The varied grades of alloy create an oxidized surface to protect it from corrosion, but when pieces of stainless steel are compressed tightly together – especially if they’re the same grade – it is nearly impossible for the atoms to differentiate themselves from one piece of stainless steel to another, so they fuse and create some of these problems:
• A bulge forms on one of the two surfaces due to the transfer of atoms. As the friction between the fasteners increases, this bulge grows and damages underlying metal.
• Threads (either male or female) can tear away from their host piece of stainless steel, completely breaking the fastener or the tool responsible for turning it.
• Molecular level-problems, which are not visible at all to the naked eye, can cause a bolt’s threads to seize or to twist off completely. Your supplier claims there’s nothing wrong with the product he’s selling you, but you continue to have these annoying instances where molecular-level problems quickly expand into something that can damage an entire machine.
Does any of this sound familiar?
Fortunately, there are ways to avoid stainless steel thread galling on your fasteners:
• When you install the fasteners, slow down the RPM speed.
• Coat individual pieces of stainless steel – especially their threads – with a lubricant and keep them well-lubricated as time and use wear on.
• Use different alloy grades for the different pieces of each fastener. Because the materials will have a different hardness, they’ll be less likely to fuse with one another.
Below is a list of common causes of galling and prevention steps.
Be sure to explore MISUMI’s vast selection of fasteners
Mar 10, 2015 About the Author Carlicia Layosa
Carlicia is the Marketing Automation Manager at MISUMI. She holds a bachelor's degree in Mechanical Engineering and a master's degree in Energy Engineering from the University of Illinois at Chicago. She is a Certified SOLIDWORKS Associate, Marketo Certified Expert, and is passionate about education and training.
I can also quote an Fastener + Fixing magazine article talk about the same topic. The article promotes their sponsor's Bumax 88 stainless steel:
Originally Posted by Anders Söderman
Overcoming galling issues with premium stainless steel fasteners
24 July 2019
By Anders Söderman, technical director, Bumax AB
Galling is a common issue with standard stainless steel bolts and can pose serious problems for critical fastener applications. However, galling can be overcome even in the most challenging of applications – particularly by selecting premium quality stainless steel fasteners.
What is galling?
Galling is a form of adhesive wear caused by excessive friction between two moving surfaces. The process involves material being torn up and transferred between the two surfaces, when they are under sufficient load, that compress the surfaces together.
Standard stainless steel fasteners are prone to galling
Standard stainless steels have a tendency to gall under certain conditions due to their properties. Thread galling can occur with standard fasteners when pressure and friction cause the bolt threads to seize to the threads of a nut or tapped hole. Severe galling, known as ‘cold welding’, can cause the two surfaces to fuse together, which makes the joint impossible to be removed without cutting the bolt or splitting the nut.
The potentially disastrous implications of galling
The consequences and implications of galling should not be underestimated. A galled fastener may not be able to achieve the necessary pre-load – especially in case of dynamic loading.
Imagine critical fasteners in the rotating parts of a chemical pump or propeller galling. The joint is likely to be subject to a fatigue breakage, which will at least require costly maintenance and downtime for the customer or end user. However, in the worst case scenario, the fatigue breakage of critical fasteners can have serious safety implications that might result in accident or injury. Galled fasteners are also much more susceptible to corrosion, which can ultimately result in breakages.
How can galling be prevented?
Stainless steel fasteners offer several properties that are essential in many critical fastener applications, such as corrosion resistance. Despite the galling tendency of standard stainless steel fasteners, the good news is that galling can be avoided by selecting premium fasteners and taking preventative measures.
It is important to consider how galling can be avoided from the outset when designing a particular fastener application in order to avoid a great deal of rework, maintenance and costs further down the line. The following advice can help solve galling issues:
• Correct material selection: Selecting the correct material for your specific application is extremely important as certain types of stainless steel are more prone to galling due to their passive chromium oxide layer and alloying elements. For example, fully hardened steel is much more resistant to galling than annealed (softened) steel. In particular, strain-hardened stainless steels that have been cold formed provide excellent galling resistance due to their improved strength and reduced ductility.
• Choose premium fasteners: As galling is common between metal surfaces in sliding contact with each other, premium fasteners that are designed to perfectly fit together can significantly reduce the risk of galling, as they minimise movement and friction. Here, high-quality threads with less surface deviations that can rub together and avoid galling issues are essential. For example, thread rolling is a premium fastener manufacturing technique that ensures greater hardness, and a higher quality and smoother thread compared with cut threads. Good quality threads with no sharp thread crest or surface defects are extremely important when producing fasteners that are far less susceptible to galling.
• Lubrication: This can reduce galling by allowing the two materials to slide past each other without causing friction. Some leading premium fastener manufacturers use custom-made wax to provide a friction coefficient of 0.10 – 0.12, which enables accurate torque calculations. Anti-seizing and anti-galling lubricants can also help reduce galling.
• Don’t use damaged fasteners: A bolt with dented or damaged threads has a significantly increased chance of galling. Check all fasteners for damage that may have occurred during shipping. Dirty bolts with debris in the threads can also greatly increase the risk of galling – so make sure you only use clean bolts.
• Careful installation: As the stainless steel passive chromium oxide layer can be damaged by high temperature and pressure, tightening bolts more slowly can reduce friction and heat that can cause galling. This may involve avoiding the use of power tools that can cause excessive friction and heat. Calculations should be made for particular applications to determine the kind of tools that can be used.
Overcoming severe galling in Japan
NARA Machinery recently invested in premium stainless steel fasteners for its powder handling machines to successfully overcome severe galling issues with standard fasteners.
The Japanese company NARA Machinery manufactures powder handling machines for various industrial customers around the world. Many of the machines require a high degree of air tightness with firmly tightened stainless steel screws. However, as screws that have powder contact cannot be lubricated, they are highly susceptible to thread galling issues.
“We previously used standard 304 and 316 stainless steel screws for all our machines, but our customers experienced galling and gorging issues with these screws,” explains Kenichi Johara, technical director at NARA Machinery. “The screws also had air leakage issues and required frequent removal for cleaning and maintenance purposes.”
Such issues and maintenance needs resulted in costly procedures and downtime for NARA Machinery’s industrial customers. “In the worst instances, galled screws had to be cut and carefully removed and replaced to protect against dust getting into the machine,” says Johara.
Johara continues: “However, we then found BUMAX via the internet and tested installing BUMAX 88 screws on a customer machine in Japan that had experienced galling issues. Since installing BUMAX screws, the customer has not reported any issues with galling or air tightness.”
Following this successful trial, NARA Machinery has recently built a brand new machine with BUMAX 88 screws. “Going forward, we plan to use BUMAX screws for all new powder handling machines we manufacture that require air tightness,” says Johara. “This will help our customers avoid the need for costly downtime due to the maintenance and replacement needs related to galling.”
The use of BUMAX 88 screws has helped NARA Manufacturing to further develop its high-quality powder handling machines. “We are very happy to have found BUMAX, and I would strongly recommend BUMAX products to other companies that experience similar galling issues,” concludes Johara.
About the author
Anders has worked in the stainless steel industry since 1995 and has been technical director at BUMAX AB since 2013. Prior to BUMAX, Anders held various positions at Sandvik Materials Technology since 1999 – including five years as strategic technology and product
development manager for Sandvik Wire and Kanthal®, six years as R&D manager for wire products and three years as a research engineer within the R&D organisation. Anders has an M.Sc. in Materials Science from Dalarna University.
This Fastenal support article also provides helpful information regarding galling prevention. After all, we as Evo owners have an excellent deck of cards when it comes to fasteners. We can go with OEM, ARP, THE, or other reputable brands from a fastener store. We can also go with custom titanium fasteners. Pick what works the best for you, and apply the proper assembly technique:
Last edited by Lightsaber; May 12, 2023 at 07:09 PM.
Reason: typo
Overall lots of information compiled here. A great deal of relevant information on the topic of hardware and their use case scenarios. I would like to point out that the UK Evo owners are electing the method of taking their rusted hardware and zinc replating it. OEM bolt finish is described as Chromate conversion coating or chem film coating. Some platers do one color but others can do both clear or gold. Looks like Mitsubishi supplier of hardware changed their process to clear as most bolts come silver whereas older bolts were yellowish gold. JIS hardware is the closest if not equivalent to OEM. I prefer to replace bolts with flanged hex bolts like ARP makes or JIS hardware if I can find it on McMaster Carr.
How to: Replace rusty high-strength engine accessory bolts
I'm not too worried about the non-critical bolts. That is, the mild steel bolts that are not on the engine. I'm confident in replacing such rusted Class 4 ones with A4-70 marine-grade stainless steel equivalents, from a reputable manufacturer like Tong Hwei Enterprise (THE).
However, I dare not try any nonsense with the rusted bolts on the engine. To prevent failure, I believe OEM and ARP are the only ways to go. Also, the hardware rust can be easily stopped by using a lanolin-based rust prevention spray, such as Fluid Film.
Sourcing some of these bolts was not easy. So I have only replaced a few selected ones that have rusted badly:
1003A010's are the bishop-shaped specialty studs like the chess piece. The OEM replacement comes zinc-plated, so no anti-seize is required. Regardless, I used my MotoMaster nickel-based anti-seize. This specific anti-seize does not reduce the dry torque much for wet tightening. I sprayed Fluid Film around the studs after replacing.
Engine cosmetic cover bracket to intake manifold bolts
These bolts have 4 radial lines on the head, probably indicating they are Class 8.8 in tensile strength. I ordered ARP 660-1016 as their replacement. I did not use the washers that come with the 660-1016. I applied a light amount of nickel-based anti-seize to protect the threads. Also, I sprayed Fluid Film around the bolts after replacing.
These are the same MF911142 Class 8.8(?) bolts. I ordered Mitsubishi OEM ones, and they come zinc-plated just like the ones the factory used. Anti-seize is not required, but I used a light amount on each. I also sprayed Fluid Film around the bolts to slow down zinc oxidation.
I have thought about using the ARP equivalents, but I ended up liking the OEM ones' larger flange heads.
These are also the MF911142 Class 8.8(?) bolts. I replaced them with new OEM ones, used a light amount of anti-seize, and spray Fluid Film after installing.
Speaking of the wire bracket bolts' torque, I'm uncertain if the Mizushima Assembly set it so high at 71 in-lbs (8.0 N·m), as the designing engineer would prefer. In the production line's reality, the valve cover and the brackets can be more flimsy than intended. Thus, if I were the production line manager, I would have no problems heading for the lower end of the designing engineer's torque specification. When replacing the plastic valve cover with the OEM aluminum one, the master mechanic at my repair shop set the torque at 60 in-lbs (6.8 N·m).
I replaced this rusty bolt with an ARP 760-1016 one. A light amount of the nickel-based anti-seize is needed to prevent ARP stainless steel from galling. I sprayed Fluid Film around the bolt after replacing.
Service Manual Group 15 Page 12 specifies that the "engine cosmetic cover bracket to intake manifold bolts" require around 71 in-lbs (8.0 N·m) to tighten.
Overall, it's a hassle to replace any high-strength bolts on the engine or transmission. Aftermarket high-strength bolts that measure up are not commonly in stock at hardware stores. So I had to either look up for the OEM part number and order from a dealership, or source ARP equivalents.
In hindsight, it's wise to spray some Fluid Film generously every now and then, so to prevent rust in the first place. These high-strength bolts are made from sophisticated metallurgy and manufacturing techniques, and they deserve the owner's attention when it comes to rust prevention.
With the talk of wet/dry torque specs in this thread, the Torque Test Channel on YouTube just released a video where they address this: The results, are expected but also beyond expectation: Skip to 16:38 to see:
How to: Replace the trunk lid damper bracket (and other rusty) bolts
