924Board.org

[Cobra too]

Hey guys I just purchased what appears to be a very cherry (8 924s. I say that as the body and interior are great but I have a couple questions about the mechanicals.....
1- excessive vibration at idle, smooth when rolling, checked mounts but don't think that's the problem....
2- there seems to be a whining noise that rises and falls with engine rpm.
3- cold start up, let our the clutch and there was a rather loud clunk from the rear of the car...
The car appears to have 150K miles but there seems to be little evidence of that. But, about 1500 miles ago the timing belt was replaced (along with valves a reworked head etc and other $ parts) might I assume this to be connected with part of my issues?

Thanks for any help, Dick.
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Having fun with my new() 924S

[fiat22turbo]

The 924S is essentially a 944 in a dancer's body. So the vibration and noise is likely a balance shaft belt that was installed incorrectly and isn't tensioned properly.

If the timing and balance shaft belts and water pump hasn't been replaced within the last 3 years or 60,000 miles. I would stop driving the car and change them or potentially suffer a failure and have to repair the head due to bent valves. In the 924S/944 world this is called a "FOES" or Front of Engine Service:

Balance Shaft belt info:

http://www.clarks-garage.com/shop-manual/eng-04.htm

Timing Belt info:

http://www.clarks-garage.com/shop-manual/eng-04.htm

Water Pump info:

http://www.clarks-garage.com/shop-manual/cool-07.htm

If the belts and pump have been changed (as in you have receipts for the parts/service), then the vibration could be an issue with dirty/leaking fuel injectors, MAF, intake leak, etc.

Good luck with the new purchase!
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[fiat22turbo]

BTW, the clunk in the rear could be a loose/broken torque tube coupler, transaxle mounts or a loose/broken CV Joint.

I'd put the rear up in the air and inspect the CV joints carefully and use a proper triple square bit to ensure the bolts are tightened properly.

Then pull the inspection covers from the bottom of the torque tube/transaxle to verify the couple bolts are properly installed and there isn't any play in the coupler.

If those aren't the issues (and they would exhibit other noises while moving), then it could be the transaxle mount(s). Many tend to fill the transaxle mount with 3M windshield weld or pourable 2-part urethane to stiffen the mounts on the cheap. There are some aftermarket replacement solutions available though if you're not the DIY type.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[Cobra too]

Thanks Fiat for the comeback and info. The records I have attained indicate the car did have a belt failure and resulting rebuild about 2000 miles ago, but, there is no indication the balance shaft belt was replaced or correctly installed or the water pump was replaced....

Is this balance shaft belt "misalignment" situation a potential failure or do I just "live" with the vibration?

Do these (wp) have a history of failure?

This little 4 banger, sounds from all I read, to be a high strung and tempermental creation. But it sure is fun!
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Having fun with my new() 924S

[Grenadiers]

Research your car on Clarks garage, look up ENG-08 for the procedure to check the balance shaft alignment. Here's the pdf file link, if it works.
http://www.clarks-garage.com/pdf-manual/eng-08.pdf

And, once gone over, FOES, new motor mounts, etc., these are very reliable engines.
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'83 944 Track car.
'88 924S Track car.
'89 944 Turbo
2004 Winnebago Vectra monster RV
2012 Jeep Wrangler
2014 Kia Soul
2001 Ford F350 powerstroke

[Cobra too]

I'm trying to ascertain here if the car is safe (relatively) to drive for a short time anyway, seeing how I am assuming the belts were not correctly installed at least the balance belt wasn't correctly adjusted.
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Having fun with my new() 924S

[ideola]

Who did the rebuild? I would not trust any DIY rebuild, and very few independent shop rebuilds. If you can't determine who did the rebuild to validate their expertise and reputation, you should assume that they did not do it correctly. If you can't do the work yourself, find a local reputable shop (do some research on Pelican and Rennlist), and have them do a thorough inspection.

You might get lucky and be able to "live" with it, but why risk it? If the car is in as good of shape as you describe, it's worth Doing It Right. In my personal experience, I've learned not to take chances with these cars, and to assume that any previous work (even work done by shops) is highly suspect.
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erstwhile owner of just about every 924 variant ever made

[Cobra too]

Thanks guys, I had an uneasy feeling about this vibration and do not live close to a shop at all so couldn't just "pop in" for an analysis. Now I will make an appointment and be able to let them have a clue as to what attention I need. Thanks again, Dick.
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Having fun with my new() 924S

[Cobra too]

Wow... belt was off one "notch", installed new mounts and determined (and replaced) rear cv joints.
WHAT A RIDE!! Love this car.
Wanna buy my factory 5???
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Having fun with my new() 924S