1989 Dual Mass Flywheel

[trainman123]

I have a 1989 6 speed with 27,000 miles on it. I had the car inspected last week. Here in NYC they run the car on a dyno. After the inspection I drove the car a few hundred feet and it started making a noise like something was banging in the engine compartment and it stopped if you reved up the engine.
1. The car runs fine untill it warms up then the noise starts. You can drive it for 25 minutes before it starts.
2. The noise appears to come from the bell housing
3. When the noise starts the motor starts to shake as if it were missing and it is not.
4. Rev the motor slightly and the noise gets less
5. the clutch is not slipping and the transmission shifts fine
6. oil pressure is fine 26 psi at idle
7. No indication of bearing or wrist pin noise on cold start up

My question is what does a Dual Mass Flywheel sound like when it is getting ready to go and is there any way to test it without removing the transmission

 

[jfreeman]

I have the identical situation - did anyone reply to this thread, or did you find a solution ???

 

[Chris Kennedy]

I am curious whether the car may be a black 6spd. that you bought from a seller in Michigan----this description sounds like one for a car I know a bit about.

Thanks,

/s/ Chris Kennedy

 

[jfreeman]

Thanks for response, but nope - mine is 91 green bought in Northeast. I am still very interested in any information on the described symptoms.

 

[G Winter]

Have you checked the balancer ?

 

[jfreeman]

I thought the DM Flywheel was factory balanced. Can it go out of balance ?? How can I check and if necessary balance ??

 

[G Winter]

I was speaking of the harmonic balancer on the front of the crankshaft. The hub on it may have cracked.

 

[jfreeman]

Thanks, I will definitely check it out. I am somewhat new to corvettes, although not cars in general. Is this a common problem ?? I am curious as to why you think this might be creating the described symptoms.

 

[Chris Kennedy]

You may want to contact the owner of ZF Doc. He's very knowledgeable about the 6 spd, dual mass flywheels etc. His email is billb@zfdoc.com He also has a website, that you can find on Google under "ZFDoc".



/s/ Chris Kennedy

 

[jfreeman]

Thanks for the referral - just sent an e-mail to billb to ask for his help in diagnosing the problem

 

[G Winter]

The balancer hub cracking isn't all that common but it does happen. It did come up on this forum within the last couple months. It is even possible that it just came lose. It is the easier of the possibles to check.

 

[Vettefreak100]

Hey what did you find out with your corvette. we just took the zf out of our vette and it was doing the exact same thing. We've looked at everthing except for taking the clutch out. We've really found nothing as of yet. Thanks.

 

[jfreeman]

Hey what did you find out with your corvette. we just took the zf out of our vette and it was doing the exact same thing. We've looked at everthing except for taking the clutch out. We've really found nothing as of yet. Thanks.

When you took the ZF out did you check the flywheel? In my case, all seems to lead to the dual mass flywheel. Based on conversations with billb@zfdoc.com , unless situation gets worse, we will replace the flywheel (and the clutch at the same time) after the end of the good driving season. At that point, will be able to observe flywheel.

 

[Vettefreak100]

I'm going to take the flywheel out sometime this week and I'll let you know what I found. I checked out the frequently asked questions on the website and saw that he said it would lead to the flywheel with the rough idle and the clicking noise it makes. This problem confuses me because our car doesn't have that many miles on it (21,000 miles) and it's not been driven hard.

 

[jfreeman]

I'm going to take the flywheel out sometime this week and I'll let you know what I found. I checked out the frequently asked questions on the website and saw that he said it would lead to the flywheel with the rough idle and the clicking noise it makes. This problem confuses me because our car doesn't have that many miles on it (21,000 miles) and it's not been driven hard.

I am very interested in what you find out. Its my guess that even though the mileage is low, just being around since '89 (mine is a '91), it is possible that two key components of the flywheel can deteriorate over time - the springs lose their tension and the two flywheel elements are , in effect, looser; and the damping material between the flywheels degrades (similar to bushing and hose deterioration).

In my case the symptoms are worse after long hot drives when at idle or low rpm from the imbalance greated by the dual-mass not being as "together" as it should be.

Please keep me posted.

-- Thanks

 

[Aurora40]

My car also has low miles, 22,000, and somewhat similar symtoms. How smoothly does your engine idle? My car idled slightly lopey until I changed the spark plugs, and I suspect that the injectors might leak slightly. I'll be trying some fuel system cleaner (Chevron Techron) and if that doesn't help, I'll be getting the injectors rebuilt. I suspect a smoother idle will solve the flywheel clunking.

 

[Vettefreak100]

This is different from a spark plug or a bad injector. I checked the plug wires and had the injectors checked out at the local machine shop to make sure that nothing was going wrong in the engine. Also things like a bad injector or a spark plug would tend to do it throughout the rpm range or lead to a loss of power. There was no loss of power in the engine at all it seemed to be running fine. This problem will sometimes come about during cold starts, but most of the time it does it after the engine gets hot. It took a few drives before I even noticed the ticking noise that the transmission was making. If you get under the car while the engine is idling you can hear the ticking noise coming from the back of the engine in the bellhousing. The L98 is usually smooth as glass and the problem would cause the engine to idle relatively rough when it happened, but it would only do it when the clutch was disengaged or it was in neutral at idle. We could run it through all six gears and never notice a problem. It could sometimes get really rough and shake the doors and it was strong enough that if I put my foot on the front tire I could feel the vibration. I hope that helps you out a little bit if you need more info lemme know.