hard to diagnose brake problem
Feb 5, 2011, 07:25 PM
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hard to diagnose brake problem
Hey everyone. I'll apologize ahead of time for the lengthy post, but I wanted to include all the info I have and all the things I've tried. I'm hoping people will take the time to read and eventually help me figure out my problem.
I've been having brake problems in my '05 for quite a few months and haven't managed to resolve it despite trying a lot of things. It's a bit hard to describe since I'm not 100% sure what's actually going on, but here's my best description:
When braking normally (street driving, basic commute), the brakes seem to feel pretty normal. When braking hard at relatively low speeds (say for something like autocross), it doesn't take much pedal force before one or multiple tires locks up (thus engaging the ABS). The brakes also don't seem to have as much "bite" as some other Evo's I've driven, but I've mostly chalked that up to different pads. Before anyone says I'm probably just braking too hard, I really want to emphasize how little braking force is generated before things slip. I've also had a couple other experienced autocrossers (some with evo's some from other cars) drive it and experience the same thing (kind of an "oh sh*t" moment at the first braking point). Oh, and I'm not left foot braking or anything that would keep it in boost during braking. It does it even if in neutral. Like I said, everyday braking feels fine, but it's been quite a while since I've had normal brakes and I don't daily drive the car anymore. Braking semi-hard from highway speeds (on an off-ramp), it seems to haul itself down alright, but I haven't really pushed it in such a situation as I'm hesitant to find out the hard way it happens there as well.
When I first noticed it, here was my setup: ferodo 2500 pads, stock rotors, motul rbf600 fluid, stainless lines all around (brakes were fine after stainless lines were installed and problems showed up nearly a year later). The only work that was done between an autocross where things felt normal and when I first noticed it (fairly long time gap I think) was having some basic fluids changed (trans/TC/rear diff/ACD bleeding).
As I've gone through my different theories about the cause of the problem, I've done the following things over the past few months (haven't had as much time to mess with it as I'd like):
- tried different tires since my old ones were pretty worn. went from old star spec's to some used, but still in good shape RT-615's. no difference, and I've also tried yet another set (almost brand new nitto 555's) with the same result. I'll also point out that the star specs and RT-615's both had plenty of lateral grip and would get nice and soft during autocross, but braking never improved.
- bled the brakes using the two man method. again, no difference.
- changed rotors since the fronts had a pretty big lip on them. no dice.
- changed brake pads (from ferodo 2500's to stoptech street pads). old pads had plenty of life left, but wasn't sure if maybe I had somehow glazed them. problem didn't go away. new (and old) pads were bled properly.
- while doing pads and rotors, checked that the pistons on every caliper could be pushed in without any unusual resistance.
- bled the brakes again using a power bleeder. no change.
- since I first noticed the problem as the ABS kicking in way too early (when a tire would lock up), I thought it might be an ABS problem. I should have checked it earlier, but I pulled the ABS fuse and tried some slow speed braking. One or more tires would lock up with only moderate pedal pressure. I've since tried this again to see if it was the same tire each time, but couldn't come to any conclusion. appears to be the fronts (no skid from the rears), but I've seen marks from both left and right sides. this makes me fairly certain the ABS is working properly and is only trying to compensate for when something locks.
- checked ABS/wheel speed rings on each axle, but again, I'm 99.99% positive there's no problem with the ABS activation at least (no clue on the ABS manifold itself).
- checked the vacuum hose running from the intake manifold to the brake booster. hose is in good shape, and I can hear a distinct hiss when the line is first disconnected from the brake booster (engine off). so pretty sure there's no leak since it holds even once the car's off, but not sure if I'm supposed to hear a hiss or not. Anyways, the pedal gets hard after a few pumps when the engine is off, and then softens back up once started (like it should).
- swapped the master cylinder and rebled the system. still no change.
- I've never noticed any fluid level change whatsoever.
- Also, the alignment was fairly mild (-1deg camber all around, zero toe) and the problem hasn't changed since having another alignment performed.
- It might all be in my head, but I also feel like there are some darker areas on my rotors that don't really go away after driving the car. They look kind of like pad deposits, but no vibrations and I can't feel any difference with my fingers. Any surface rust that accumulates disappears after driving and my wheels get filthy with brake dust as easy as they ever did. So the brakes are clearly doing something. The dark areas could just be from the last stop I came to, but I'm not sure.
One other note is that at some point I got tired of not having time to mess with it and drove it a little ways to have a local, reputable Evo shop (Speed Element) take a look at it. For the first time since the problem first presented itself, I couldn't replicate it once there (go figure). The shop owner rode along with me, and the brakes felt fine. He then drove the car (owns an X) and he said they also felt normal. I left thinking maybe it really had been the tires since I had just swapped to new wheels/tires and hadn't tried any hard braking yet. Of course I wasn't so lucky and I can pretty much recreate it anytime I brake semi-hard. The only variable I can think of with driving there is that I spent way more time on the highway pulling vacuum then I ever do in other driving. I've noticed once or twice that the pedal felt firmer after exiting from a long highway stint, but I can't figure out how that could relate to my problems since the vacuum line and brake booster seem okay. Plus, the car had been parked and turned off for several minutes before going for the test drive.
And that's where things currently stand. There are only so many components in the brake system, and I feel like I only have a few left before I've changed damn near all of them.
If anyone has any other ideas or has ever had something like this before, I'd really appreciate any help. It's something that has dragged on for months and months, and it's frustrating being able to out-brake an Evo in my girlfriend's stock VW golf or my 20 year old E30 daily driver, both with crappy all-season tires.
Again, sorry for the incredibly long post, but thanks for reading this far.
I've been having brake problems in my '05 for quite a few months and haven't managed to resolve it despite trying a lot of things. It's a bit hard to describe since I'm not 100% sure what's actually going on, but here's my best description:
When braking normally (street driving, basic commute), the brakes seem to feel pretty normal. When braking hard at relatively low speeds (say for something like autocross), it doesn't take much pedal force before one or multiple tires locks up (thus engaging the ABS). The brakes also don't seem to have as much "bite" as some other Evo's I've driven, but I've mostly chalked that up to different pads. Before anyone says I'm probably just braking too hard, I really want to emphasize how little braking force is generated before things slip. I've also had a couple other experienced autocrossers (some with evo's some from other cars) drive it and experience the same thing (kind of an "oh sh*t" moment at the first braking point). Oh, and I'm not left foot braking or anything that would keep it in boost during braking. It does it even if in neutral. Like I said, everyday braking feels fine, but it's been quite a while since I've had normal brakes and I don't daily drive the car anymore. Braking semi-hard from highway speeds (on an off-ramp), it seems to haul itself down alright, but I haven't really pushed it in such a situation as I'm hesitant to find out the hard way it happens there as well.
When I first noticed it, here was my setup: ferodo 2500 pads, stock rotors, motul rbf600 fluid, stainless lines all around (brakes were fine after stainless lines were installed and problems showed up nearly a year later). The only work that was done between an autocross where things felt normal and when I first noticed it (fairly long time gap I think) was having some basic fluids changed (trans/TC/rear diff/ACD bleeding).
As I've gone through my different theories about the cause of the problem, I've done the following things over the past few months (haven't had as much time to mess with it as I'd like):
- tried different tires since my old ones were pretty worn. went from old star spec's to some used, but still in good shape RT-615's. no difference, and I've also tried yet another set (almost brand new nitto 555's) with the same result. I'll also point out that the star specs and RT-615's both had plenty of lateral grip and would get nice and soft during autocross, but braking never improved.
- bled the brakes using the two man method. again, no difference.
- changed rotors since the fronts had a pretty big lip on them. no dice.
- changed brake pads (from ferodo 2500's to stoptech street pads). old pads had plenty of life left, but wasn't sure if maybe I had somehow glazed them. problem didn't go away. new (and old) pads were bled properly.
- while doing pads and rotors, checked that the pistons on every caliper could be pushed in without any unusual resistance.
- bled the brakes again using a power bleeder. no change.
- since I first noticed the problem as the ABS kicking in way too early (when a tire would lock up), I thought it might be an ABS problem. I should have checked it earlier, but I pulled the ABS fuse and tried some slow speed braking. One or more tires would lock up with only moderate pedal pressure. I've since tried this again to see if it was the same tire each time, but couldn't come to any conclusion. appears to be the fronts (no skid from the rears), but I've seen marks from both left and right sides. this makes me fairly certain the ABS is working properly and is only trying to compensate for when something locks.
- checked ABS/wheel speed rings on each axle, but again, I'm 99.99% positive there's no problem with the ABS activation at least (no clue on the ABS manifold itself).
- checked the vacuum hose running from the intake manifold to the brake booster. hose is in good shape, and I can hear a distinct hiss when the line is first disconnected from the brake booster (engine off). so pretty sure there's no leak since it holds even once the car's off, but not sure if I'm supposed to hear a hiss or not. Anyways, the pedal gets hard after a few pumps when the engine is off, and then softens back up once started (like it should).
- swapped the master cylinder and rebled the system. still no change.
- I've never noticed any fluid level change whatsoever.
- Also, the alignment was fairly mild (-1deg camber all around, zero toe) and the problem hasn't changed since having another alignment performed.
- It might all be in my head, but I also feel like there are some darker areas on my rotors that don't really go away after driving the car. They look kind of like pad deposits, but no vibrations and I can't feel any difference with my fingers. Any surface rust that accumulates disappears after driving and my wheels get filthy with brake dust as easy as they ever did. So the brakes are clearly doing something. The dark areas could just be from the last stop I came to, but I'm not sure.
One other note is that at some point I got tired of not having time to mess with it and drove it a little ways to have a local, reputable Evo shop (Speed Element) take a look at it. For the first time since the problem first presented itself, I couldn't replicate it once there (go figure). The shop owner rode along with me, and the brakes felt fine. He then drove the car (owns an X) and he said they also felt normal. I left thinking maybe it really had been the tires since I had just swapped to new wheels/tires and hadn't tried any hard braking yet. Of course I wasn't so lucky and I can pretty much recreate it anytime I brake semi-hard. The only variable I can think of with driving there is that I spent way more time on the highway pulling vacuum then I ever do in other driving. I've noticed once or twice that the pedal felt firmer after exiting from a long highway stint, but I can't figure out how that could relate to my problems since the vacuum line and brake booster seem okay. Plus, the car had been parked and turned off for several minutes before going for the test drive.
And that's where things currently stand. There are only so many components in the brake system, and I feel like I only have a few left before I've changed damn near all of them.
If anyone has any other ideas or has ever had something like this before, I'd really appreciate any help. It's something that has dragged on for months and months, and it's frustrating being able to out-brake an Evo in my girlfriend's stock VW golf or my 20 year old E30 daily driver, both with crappy all-season tires.Again, sorry for the incredibly long post, but thanks for reading this far.
Last edited by grahamab; Feb 5, 2011 at 07:34 PM. Reason: forgot something....
Feb 6, 2011, 09:09 PM
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I'm not a brake expert, but here goes nothing....
Isn't the vacuum booster supposed to reduce the pedal effort required to achieve the same braking force? If that's true, you'd think the problem would be worse with higher vacuum levels. Maybe you could disconnect the line and try recreating the problem with zero vacuum to try to rule that out? Just be sure to do so in a controlled environment with plenty of run off space available....and eat your wheaties
Have you modified your suspension significantly? Specifically, is it extremely stiff or underdamped, which could cause the tires to loose contact with the road surface? Maybe your shocks are blown? Also, are you running unusually high or low tire pressures? This could cause a loss of traction as well.
Another thery I have is the ferodo pads may have been too agressive for your tires (even sticky tires). When you switched to the stoptech's, did you resurface the rotors? If not, my guess is that you may still have some ferodo pad material on them that the less aggressive pads are having a hard time wearing off. This aggressive material may have even embedded itself in your new pads, resulting in similar modulation problems as when you had the ferodo's on there. That's all speculation (again, not an expert), but I do know that as brakes heat up, material transfers from the pads to the rotors. If it doesn't transfer evenly, you get the sensation of a warped rotor (not the problem in your case, of course). Really aggressive pads can fix the problem by essentially turning each rotor into a brake lathe, which removes all the old material (check out the link for more info). Or you could just turn the rotors you have or get new ones.....
http://www.stoptech.com/tech_info/wp_padremoval.shtml
I'm going out on a limb here...is it possible that the new fluid in the ACD is causing it to malfunction somehow, causing uneven distribution of torque? I know pretty much nothing about the system, so I'm probably completely off base with that comment.
Since you weren't able to recreate the problem after the long drive to the guy's shop, maybe you could try letting the car cool down before you take it for a spin.
Well, that's all the guessing that I can do for one night. I know how frustrating it is to have a machine get the better of you for so long...
Isn't the vacuum booster supposed to reduce the pedal effort required to achieve the same braking force? If that's true, you'd think the problem would be worse with higher vacuum levels. Maybe you could disconnect the line and try recreating the problem with zero vacuum to try to rule that out? Just be sure to do so in a controlled environment with plenty of run off space available....and eat your wheaties
Have you modified your suspension significantly? Specifically, is it extremely stiff or underdamped, which could cause the tires to loose contact with the road surface? Maybe your shocks are blown? Also, are you running unusually high or low tire pressures? This could cause a loss of traction as well.
Another thery I have is the ferodo pads may have been too agressive for your tires (even sticky tires). When you switched to the stoptech's, did you resurface the rotors? If not, my guess is that you may still have some ferodo pad material on them that the less aggressive pads are having a hard time wearing off. This aggressive material may have even embedded itself in your new pads, resulting in similar modulation problems as when you had the ferodo's on there. That's all speculation (again, not an expert), but I do know that as brakes heat up, material transfers from the pads to the rotors. If it doesn't transfer evenly, you get the sensation of a warped rotor (not the problem in your case, of course). Really aggressive pads can fix the problem by essentially turning each rotor into a brake lathe, which removes all the old material (check out the link for more info). Or you could just turn the rotors you have or get new ones.....
http://www.stoptech.com/tech_info/wp_padremoval.shtml
I'm going out on a limb here...is it possible that the new fluid in the ACD is causing it to malfunction somehow, causing uneven distribution of torque? I know pretty much nothing about the system, so I'm probably completely off base with that comment.
Since you weren't able to recreate the problem after the long drive to the guy's shop, maybe you could try letting the car cool down before you take it for a spin.
Well, that's all the guessing that I can do for one night. I know how frustrating it is to have a machine get the better of you for so long...
Last edited by Lost Viking; Feb 6, 2011 at 09:12 PM.
Feb 7, 2011, 06:47 AM
#3
Have you tried to see if there are any ABS codes? I think the MUT reader at the dealer or a good shop with an advanced reader will be the only thing that will work reading it.
I had an issue like this on my SVTF. If bleed in the incorrect order, 1 rotor/caliper will drag. The ABS on that car goes fubar with the wrong order. We've never been able to 100% find out the whole reasoning.
You're using the service manual bleeding order for corners and bleed ports, right?
I had an issue like this on my SVTF. If bleed in the incorrect order, 1 rotor/caliper will drag. The ABS on that car goes fubar with the wrong order. We've never been able to 100% find out the whole reasoning.
You're using the service manual bleeding order for corners and bleed ports, right?
Feb 7, 2011, 06:56 PM
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Thanks for the replies and various ideas.
something worthy trying. you're right, I should make sure I have plenty of run-off room.
First showed up when I had Bilstein's and Swift Spec R's. Had been fine for a long time on those before this popped up. I'm now on coilovers, but nothing crazy in my setup and, like I said, started before my current suspension setup.
I ran those pads for about 10-15,000 miles without any problems and can't see that being a problem considering how many people on here run them with a variety of tires. I also switched to new rotors with the new pads (proper bedding procedure), so no pad carryover.
I'm also not an expert on the ACD system, but I could never figure out how it could be related to my brakes. I included the service in case someone knew a connection, but my understanding is that the center diff is open during braking. Not sure though.
I haven't tried pulling codes, but I assumed there weren't any if the ABS light wasn't on (is this wrong?). I also thought the system was essentially left open when the fuse is pulled, leaving the fluid to go freely based on the proportioning valve.
I'm also fairly certain I've been using the correct bleed order. Right rear, left front, left rear, right front. Both nipples at each caliper.
If anyone has other ideas, definitely let me know.
Have you modified your suspension significantly? Specifically, is it extremely stiff or underdamped, which could cause the tires to loose contact with the road surface? Maybe your shocks are blown? Also, are you running unusually high or low tire pressures? This could cause a loss of traction as well.
I'm also fairly certain I've been using the correct bleed order. Right rear, left front, left rear, right front. Both nipples at each caliper.
If anyone has other ideas, definitely let me know.
Feb 9, 2011, 04:29 AM
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Did you start the engine while bleeding as directed in the small text by the last picture? Maybe the newest ABS technology needs to be energized during the bleeding process.
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Feb 10, 2011, 06:38 PM
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I didn't, but I think that's for mitsu service so they can use some other software to cycle the ABS unit and purge the fluid from that as well. I'm guessing most people on here don't start the engine when bleeding, and I've done it in the past and I never had this problem. my problems also seemed to pop up long after any brake work had been done.
Feb 11, 2011, 09:38 AM
#9
I had the same problem and it turned out to be a very slightly cracked tone or target ring (what I think you are calling a speed ring?). From visual inspection on the car I couldn't see it. I tried all shorts of things; no avail. I lived with the problem for about a half year and it became more problematic and I looked at the rings again and found an ever so small crack. Fixed that and all problems gone.
Feb 11, 2011, 08:40 PM
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sorry, I was calling it the ABS ring or the wheelspeed ring (some cars use the same sensor for wheelspeed...not actually sure on the Evo). but yeah, same thing you're talking about.
I remember seeing people post about problems related to damaged rings causing ABS problems when I was searching a while back, but I can't see how a damaged ring would cause problems when the ABS is disabled (by pulling the fuse). at that point, the brake system wouldn't be using any information from the sensor, right? I could be wrong and maybe there's damage to one that I just can't find, but I don't see how it would affect braking without ABS. anyone have any thoughts on this?
I remember seeing people post about problems related to damaged rings causing ABS problems when I was searching a while back, but I can't see how a damaged ring would cause problems when the ABS is disabled (by pulling the fuse). at that point, the brake system wouldn't be using any information from the sensor, right? I could be wrong and maybe there's damage to one that I just can't find, but I don't see how it would affect braking without ABS. anyone have any thoughts on this?
Feb 14, 2011, 12:48 AM
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Ideas,
-Bad brake hose at calipers, particularly the rears. Brake hoses break down internally (the inside rubber deteriorates) and can cause brakes to stick or not work at all. Are the rear brakes working? Clamp off the front brake lines (pull the lines off the calipers and find come brass caps to install) and see if the rears will stop you.
-ABS valve block bad, poss debris in ABS valves. Even when ABS is disabled, fluid still flows (or tries) through it.
-Bad brake hose at calipers, particularly the rears. Brake hoses break down internally (the inside rubber deteriorates) and can cause brakes to stick or not work at all. Are the rear brakes working? Clamp off the front brake lines (pull the lines off the calipers and find come brass caps to install) and see if the rears will stop you.
-ABS valve block bad, poss debris in ABS valves. Even when ABS is disabled, fluid still flows (or tries) through it.
Feb 14, 2011, 07:54 PM
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I might want to be sure the rear's work before blocking off the fronts.
I don't think the fluid is completely blocked since it comes out fine during bleeding. I suppose there could be a blockage somewhere that's restricting flow, but I'm not sure how to track it down.
I don't think the fluid is completely blocked since it comes out fine during bleeding. I suppose there could be a blockage somewhere that's restricting flow, but I'm not sure how to track it down.
Feb 21, 2011, 09:26 PM
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just a small update since I had a little time to mess with it today. put it up on jacks and went through each caliper and piston to make sure that applying the brake pedal made each piston come out. didn't see any problems and every piston would move just fine when I would try to hold the others in place. I'm pretty much stumped and don't know what else to even look at. it's to the point I almost just wish I could sell the evo and be done with it.