ROB-80E

Hi Everyone, hoping you can throw some ideas at me as to this noise i've got when the engine is idling. I'll give you as much info as I can, and will post the link to the vid at the end.

Engine - Evo VIII 4G63, freshly rebuilt and stroked to 2.3L. The noise has existed since day one of engine start post rebuild. The engine has now been running for approximately 2 months and has done around 800miles. The noise has not gotten worse, nor has it gotten any better.

The noise only occurs once operating temp has been reached (gradually starts as temp comes up) and appears to be timing belt related. The noise CAN be stopped! By inserting a Timing Belt Tensioner Tool (as seen here) until it contacts the Tensioner Arm, and then if the tool is tightened by turning clockwise a further 1/4 turn (compressing the Auto Tensioner), the noise stops. 1/4 turn counter-clockwise and the noise will reappear.

Timing belt tension seems normal. I have GSC R2 cams and GSC Springs and retainers in the head. At TDC, I have approximately 15mm of belt deflection between the cams, anwhere else I have minimal and might be borderline too tight. Timing Belt "pre" tension has been redone 3 times according to the WSM. I've tried setting this at both TDC and away from TDC with no change to the final outcome...noise is still present at operating temp. ALL belts, bearings and the auto tensioner is brand new OEM (not ruling out that one of these components may be faulty from OEM though).

The noise occurs regardless of whether the engine side plastic covers are installed or not.

I've used a stethoscope to try and pin point the source of the noise, however, no joy...it's quite difficult to safely get to a lot of the components with the engine spinning at 1000rpm.

Balance shaft belt has been loosened from my original tension which was in spec, again no change.

Approx 30-40psi oil pressure on idle. The noise seems to go away as revs rise, although, it may be just that the frequency merges into one and is overcome by engine noise making it inaudible.

Anyway, there may have been a few more things which i have tried and or forgotten to mention.

Would love you hear if you've experienced anything similar or have any ideas to share to so what could be the cause here.

VIDEO OF "THE NOISE"

Note: i'm not referring to any rattles that you may hear. It's the rubbing or almost like dry bearing sound.

Thanks in advance.

galantman03

iTrader: (7)

Ill throw out an idea. this bearing http://www.streettunedmotorsports.co...ner_pulley.htm

Since when you tighten the tensioner tool which RELEASES pressure on that maybe the bearing is bad when the belt tension is place on it... Idk throwing that out there

ROB-80E

Thanks mate.

Yeah, I'm begging to see this as an exercise of literally replacing each component (including the belt) one by one until the noise stops.

I replaced the Auto tensioner tonight in hope, but no, this didn't stop the issue.

A concern i now have, is that the noise really does sound like its coming from the crank area. Eg, a screwdriver just below the sump join to the block close the crank manages to echo the noise quite clearly. If it was something to do with a bearing internally, i'd expect releasing tension on the accessory belt would have the same effect as reducing tension on the timing belt using the tool.

Really can't be bothered replacing each component one by one. lol

lostsoulsevo

iTrader: (10)

My car had similar issues. Ending up being the timing belt was to tight. So either yours is to tight or a pulley is bad. Did you replace all the pullies?

galantman03

iTrader: (7)

what about the trigger plate for the cas. Is that rubbing on say the CAS? or just bent enough to rub but not damage it. just throwing it out

ROB-80E

lostsoulsevo - Already tried different belt pretensions. At one point, I had over 20mm of belt deflection between the cams at TDC. No change to the noise. All bearings were replaced. The actual toothed pulleys are the same as prior to rebuild. This noise has only been present post rebuild.

galantman03 - The trigger plate for the CAS does not appear to be damaged in any way. There is ZERO contact to the CAS. I thought that a belt may have been rubbing on the plate or even on the back of the harmonic balancer, but I ran the engine without it for a few seconds last night, and again, no change.

Appreciate the idea's guys. Please keep them coming!!

Tonight I'm going to swap the belt itself. I have a good condition spare that I can put on there to test with. I have a feeling it's going to be the idler bearing that sits just behind the power steering pump bracket...of course it's the most painful one to replace.

Siege

iTrader: (2)

Did you ever figure out the cause of your noise? Experiencing a similar noise after a Timing Belt, Balancer Belt replacement.

ROB-80E

It was the Evo 9 belt doing it for me. I put a used Evo 8 belt on and the noise went away. In the end I just fitted the new evo 9 belt and built a bridge to get over the new noise.

It's been driven and raced hard for years now....no issues.

Siege

iTrader: (2)

Thanks, I really appreciate the response!