Rattle Underneath

[Twinmags]

I'm getting a rattle from underneath my '91 Z, it has 28,000 miles and I'm stumped. The rattle goes away when I press in the clutch. Any thoughts?

Hmm yep everyone has hit the nail on the head but look at the heat shields for the Cats as well. Might be a combination of noise.

[marc.madmax]

typically that is the throw out bearing on a clutch. some wait but I think you may damage the input shaft on the transmission if you do. look at replacing the clutch when you do it since you have to pull the tranny to replace it.

[tomtom72]

I would humbly suggest also remembering that we use dual mass flywheels and that they are prone or can make some strange noises with the trans in neutral and the motor at idle speed.....some make an occasional thud or thunk or sound kind of like a diesel motor...you know that rattle that diesel's make at idle. Also sometimes due to the nature of the cut of the trans gears in 1 thru 4(?) the trans makes rattling noises. Our gears are straight cut in 1 thru 4 like the old M22's & can make a bit of a racket in neutral....that is also what makes the gear noise we hear at low speeds in 1st especially.

Over at zfdoc.com there is a great Q & A section on the throw out bearing and some of the noises that it can make and some "do it yourself" tests to use. Also the Q & A section is generally devoted to our trans & it's associated parts with great tips for some simple trouble shooting.

:thumbsup: :cheers:
Tom

[WB9MCW]

TRANNY SYNCRO RATTLE SAME SOUND I GET SINCE I HAVE AN ALUM FLYWHEEL AND NO DUAL MASS STOCK UNIT--THE REASON FOR THE DUAL MASS IS TO QUIET THIS EXACT THING---
TOMTOM WAS ON THE MONEY WITH THE GEAR ANSWER--PROLY UR DM FW IS SHOT!

[rkreigh]

listen closely when you shut the car down. often a bad dual mass will rattle and bang a bit as the car turns off.

a "mechanics stethescope" which is nothing more than a rod attached to some tubine is great for trouble shooting rattles. get the car up on a lift and listen with the "scope" and I'm sure you'll figure out where it's coming from.

the single mass flywheels give the "rattle all the time" at idle with the the clutch out and give the zr1 a bit of a diesel truck clatter type sound from the gears in the ZF banging around. it doensn't hurt anything though.

I love the light flywheel, but the noise is annoying.

hope this helps.:mrgreen:

[xxxscimitarxxx]

Hi to All

Ive been trawling the threads for dual mass flywheel issues and this one seems relavant to me

just got my 92 shipped into UK, and while l havent driven it (seen it)yet, the guy who picked it up for me says there is a definate knock at idle.(he hasnt driven it either , just started it and let it warm up)

discounting crankshaft bearing related problems lm hoping its at worst the flywheel. I havent discounted it may have been replaced already with a single plate fidanza type and therefore it seems knocks and rattles go with those, but thats only a guess

Anyway, l will get to see car soon and work out where noise is coming from.

In the meantime (in the absence of manuals to hand) and taking it for a run, my main questions are

1)If it is stock dual mass flywheel problem, can l carry on driving it as normal(ish) without doing any harm.

2) does a problem flywheel cause regular spaced sounds or irregular

3) can a worn out harmonic balancer cause knocking

4) could it be a bad injector

are there any uploaded sound files of engine faults?

[tomtom72]

I'll speak up till Jeff or one of the other more experienced guys see your Q's.:o

#4 = yes if the injector's coil or/and spray pattern is causing a miss in that cylinder; then the irregular cylinder power output causes the D/M to knock. Same to applies to an issue with the plugs and/or coils if they are causing a miss.

#3 = that's a good Q as our balancers can have slippage with the rubber between the inner & outer rings. I just can't figure out how it would cause a knocking noise unless some part of the balancer was actually hitting something, but I don't think that would sound like the kind of deep thunking or knocking sound at odd intervals that is characteristic of a "miss" induced knock from the D/M flywheel.

#2 = if it's miss induced yes. If the D/M is actually bad I would guess that it would knock at shut down. I do not know for sure what it would sound like at idle if the springs &/or diaphram were bad....maybe it would be regular even timmed knocking.

#1 = Well if it were bad I wouldn't do any 6800 rpm run-ups...:redface: I would guess it might fall apart????

as an aside. I listen when I shut down to hear any thunks or knocks from the trans tunnel/firewall area. I know for sure that when my injectors went out my car sounded like there was a boulder rattling around in my bellhousing. I also have observed that when my std ACDelco plugs get past the sweet spot, my idle quality starts to suffer & I get the oddly spaced "knock" from the D/M. Just one "knock" and no real regularity to it either and it's not all that pronounced.

Sorry I don't have more...

:cheers:
Tom

[xxxscimitarxxx]

That was plenty.....thanks very much for taking the time to tell me all that

I also read that injectors or misfire can cause the D/M to knock....but having not been shown, you wouldnt think such a small thing would have such an effect.....l will get that checked out

at least my fears of bottom end, crankshaft bearing failure, seem at this stage to be receeding

However, lve got a wtb thread for a serviceable engine going, but its something l would rather not need right now.....my cars only a baby with 110,000 miles on it

[rhipsher]

It could also be a cat failing. All you have to do to check it is get under the car with a rubber mallet and tap on your kats. And if it rattles like there's a bunch of loose rocks in there then thats it. And if it is! Been there done that. And if your lucky you have a 93 and up because the cats are just bolted on. If your unlucky and have a 90-92 they are welded on. And you have to remove the entire manifold as one piece.

[xxxscimitarxxx]

Thank you for that.....

Its good to know that the worst possible thought you can have about a problem is probably just that......the worst ''possible''..... and not neccessarily the worst ''probable''

Ive got a good list of things to check when l get home

Thanks again

Dave

[cuisinartvette]

You have been doing some research for sure!
Bet its nothign more than typical dual mass noise.
Bottom ends rarely fail in these.

[xxxscimitarxxx]

From all that lm hearing lm relieved to think it is the dual mass for what ever reason it is, misfire,injector, dual mass itself....none of which is to herrendous to sort out.....

as said before l havent actually heard the car running yet ....lm going on what ive been told by the freind whos collected it for me. he is knowlegable on US classics in the UK but not the ZR1 in particular. That being said....he says it warms up fine, idles nicely apart from the noise described, good oil pressure, temperature good, doesnt smoke, no codes showing up.

l get home in a couple of weeks so will put the received opinions to test and get to the bottom of it.

Thanks to all :worship: and hope the originator of this thread accepts my thanks for having hijacked it

Dave Austin

[Z51JEFF]

That was plenty.....thanks very much for taking the time to tell me all that

I also read that injectors or misfire can cause the D/M to knock

Yes indeed,mine did the same thing when one injector died.If you didnt know about the fly wheel it would be very easy to assume the engine had a bad knock.

[xxxscimitarxxx]

whats the method to test for and locate a bad injector...lm assuming that with the suggested DM relation we are talking primary injectors

[billybaloneey]

It could also be a cat failing. All you have to do to check it is get under the car with a rubber mallet and tap on your kats. And if it rattles like there's a bunch of loose rocks in there then thats it. And if it is! Been there done that. And if your lucky you have a 93 and up because the cats are just bolted on. If your unlucky and have a 90-92 they are welded on. And you have to remove the entire manifold as one piece.

I've only had my '94 for a short time, but after it's started, I hear a noise for a short time (5-10 seconds) that sounds like a can with a few dimes in it, being rattled. The seller was in China, and his sister was handling the transaction. When I heard it for the first time it kinda sounded a little like a rattling through-out bearing, but not exactly, so it had me worried. I noticed the noise went away almost immediatedly and never returned during the test drive. When I returned from the test drive I mentioned it to her and she said their mechanic said it was the cat(s), and that it was a common problem.

Thanks for the, rubber mallet, tip. I'm in the process of changing out my radiator...when I have some free time...so I'll already be under there, and tap them a few times.

The failing cat(s) brings up another question:

I thought the cat's were part of the emission system. If they were failing or already failed, wouldn't there be codes being generated? Mine is not displaying any codes. I remember seeing a post a long time ago about bypassing the cat's...or gutting them...but I can't remember if the post mentioned having to deal with computer related codes.

[rhipsher]

I've only had my '94 for a short time, but after it's started, I hear a noise for a short time (5-10 seconds) that sounds like a can with a few dimes in it, being rattled. The seller was in China, and his sister was handling the transaction. When I heard it for the first time it kinda sounded a little like a rattling through-out bearing, but not exactly, so it had me worried. I noticed the noise went away almost immediatedly and never returned during the test drive. When I returned from the test drive I mentioned it to her and she said their mechanic said it was the cat(s), and that it was a common problem.

Thanks for the, rubber mallet, tip. I'm in the process of changing out my radiator...when I have some free time...so I'll already be under there, and tap them a few times.

The failing cat(s) brings up another question:

I thought the cat's were part of the emission system. If they were failing or already failed, wouldn't there be codes being generated? Mine is not displaying any codes. I remember seeing a post a long time ago about bypassing the cat's...or gutting them...but I can't remember if the post mentioned having to deal with computer related codes.
I didn't have any codes either. But when I had it at coreys for some other work I told him about the rattle. He didn't even know what it was. After he had cleaned and flow tested my injectors he put it on the dyno and as soon as he put his foot in it a big chunk of the drivers side cat blew out of the exhaust and hit the back bay door. He sold me a pair of manifolds with cats off a 90 Z he had lying around for $500. He said if he does the work I'm looking at about 14 hours of labor. He encouraged me to do it myself and said It wasn't rocket science but it was very labor intensive. So I did it myself and it took me 18 hours. There were loose chunks of cat material throughout the whole exhaust system so I had to take it apart and shake it out. But when I was done no more rattle. Good as new. My hands were cut up and swollen for three days after that. But like I said you only have to go through that hellish nightmare if you have a 90-92.:thumbsup: PS when I took the old manifolds off I could pick them up and shake them and hear the same sound that baffled me for monthes. And at that time people on this site were saying the same things about what the rattle could be. But nobody ever mentioned that it could be caused by the catylatic converters going bad. I am just tying to help out based on my own experiances owning this wonderful car. As is everybody else on this site. But somtimes the only way to tell whats wrong is when it finally blows up on you.

[tomtom72]

whats the method to test for and locate a bad injector...lm assuming that with the suggested DM relation we are talking primary injectors

I just am not sure that I know "a definitive" way to check for one /and or multiple bad injectors. I would put a scanner on the motor and look to the fuel numbers. I would sniff the exhaust, as ya can smell a lean motor or at least I could smell the lean condition in my case when the injector coils failed. I would pull the plugs and read them with respect to what the left and right fuel numbers were saying from the scan. I would do an ohm test on the injector coils in cold and hot conditions. I would make sure to eliminate the ignition coils as being good and ohm the plug wires. You can ohm a pair of plug wires by doing the test on a "paired" set of wires and you also get to have a static ohm test on that ignition coil....ya know one plug wire end thru that coil to the other plug wire end.

Just as an aside when I had injector coil failure. There was a BIG miss as I had four coils fail all on one bank.....it was rather obvious in hind-sight what the root of my miss was but as a rookie Z owner I was lost. Those coil failures made my Z sound like a M/B 300 D...the plugs on that bank told me there was no gas, the exhaust smell from that bank's exhaust tips told me that bank was big time lean, the fuel numbers from the scan were what threw me for a loop. I had no experience with EEC at that point in time so I did not realize what those numbers were telling me. Oh, forgot this injector coil symptom. As the inj coils heat up the miss gets worse. On cold start the miss & lean exh smell was almost not there. As the motor got to normal coolant temp the miss & lean smell grew worse, as the inj coils heated up their shorts in their coils got worse cutting off more fuel.

If the injectors have an issue with the nozzels I would also look to the O2 readings and the cross counts(?) on the scan. I would expect to smell a rich condition at the exh tips and I would think that you would also see the rich condition at the plugs' electrodes. Ofcourse you also have to run down the ignition system for proper operation. Ofcourse if the nozzels are clogged then I would look to see that I smell that & see that at the exh and the spark plugs and on the scanner.

Sorry to be so long about this....I'm sure if I had a better understanding of EEC I could be more concise about this....the last car that I owned that I actually worked on had a holley 4bbl carb!

:cheers:
Tom

[xxxscimitarxxx]

That was plenty Tom

ive got the '11 times only' datamaster scanning software.....will that work for me....lve never used it before.....lve never used scanners before:iamwithst
Other than that you were dead right of course....

use my eyes, nose, and a few simple electrical test tools....visual plug condition, smell, electrical test the injector coils, plug leads. coil packs

common sense if someone pokes you with it.

Cant thank all you guys enough.

For all that have helped. Im sorry lm not near enough to buy you all a drink.

[tomtom72]

:thumbsup:Dave!

That's why we are called The Brothers of The Beast!

Ya never know.....a pint a guinness & a wee bit o dram makes the world appear to be a more civilized place....we may cross paths and we'll raise that pint and have a good laugh!

:cheers:
Tom

forgot.....yes the datamaster would give the same data as a regular scanner, but I believe that it is more detailed as far as sampling data over time....I think. I've never used those software programs before so I'm not too clear on what all it exactly displays.