Asking for help with noise (clutch) diagnosis

[Duff]

I have developed a mechanical (clanking) sound that seams to be coming from the clutch area. It has gotten gradually worse over the past few weeks and is now fairly loud at idle. It sounds like the something doesn't completely disengage when the clutch is in, It's kind-of a metalic rattling/tapping sound.

It only happens when the clutch is depressed at idle and gets louder and more consistent after the car is driven and heats up. (barely noticable at start-up). The clutch engages and shifts fine and there is no sound while in gear.

When detailing the car over the winter, I noticed fluid aroung the slave and the reservior was slightly low. I never noticed the sound until I topped off the fluid.

Based on what I've read, I believe the slave is going bad, so I am going to replace it anyway, but my question really is, would a bad slave cause the sound I'm describing by not completely disengaging the clutch? I don't feel any pull when stopped.

Any help is greatly appreciated

[QB93Z]

How many miles on the Z and how often is it driven.

Without hearing the noise it is hard to troubleshoot. If the clutch disengages and engages properly, it is probably not the clutch or slave cylinder causing the noise.

The noise may be coming from the Dual Mass Flywheel. Usually the noise is caused by an engine miss that causes the engine rotation to be uneven and the flywheel noise results.

Since your ZR-1 is a 1990, if the injectors have never been replaced, that is most likely the cause of an engine miss. Original 1990 injectors eventually go bad when they are exposed to ethonol mixed fuels.

I replaced the injectors in four 1990 LT5's in the last year, and all 4 cars had three or more failed injectors.

Also, Check for good plugs, plug wires, and coils.

If you need someone to help investigate and repair your ZR-1, Rick (Rickyrj1) is about 1.5 hours from you and there is a lot of help available here in the Baltimore area (2-2,5 hours away).

Jim

[Duff]

Jim, thanks for the response.

The car has just under 12,000 miles and not driven a lot (1,000/year and stored in winter).

I've been doing some more research since I posted and came across the DMF issue as you suggest. Sounds like the problem to me, although I know I need and to replace the slave and bleed the clutch hydraulic system. From reading some info on the ZFDoc site, the system needs maintenance.

I wouldn't say I have a bad mis or real rough idle but I'm going to listen more closely tonight. As I said, the noise has been getting worse over the last few weeks and definately gets worse after warm up (which correlates to the injectors failing more as they heat up) and I kind of noticed a drop in performance last night. I also know I have a vacuum leak under the plenum so I was going to do a pull as next winter's project but it looks like that may have to be moved up. From what I've read, I'm sure the injectors are, or are going bad.

I mainly wanted to get a direction of where to start.

Again thanks for your suggestions and It's nice to know there is help near by if I need it.

[GOLDCYLON]

Hi there Duff welcome aboard. I Suggest replacing the Slave ASAP. The sound you may be hearing could be coming from a couple of places. The Dual mass flywheel for one and the fork and bearing if the slave is failing. Speaking to the ZFDOC in the past most chose to replace both the clutch master and the slave master at the same time. As the ZFDOC has indicated a poor funtioning Slave in the beginning of the end of most ZF transmissions. Knowing Bill for about 5 years now what he tells me is (IS).

As to the injectors most of us have either gone to RC injectors, Accels or FICs. The RCs are the most expensive and you need 16 of the little buggers to get the job done. Your car if its not driven much is prone to injectors failure as the injectors tend to rust and pit over time. The OEM injector also can not tolerate modern fuel additives that we put into our fuels today for EPA reasons so they tend to fail. The RC injectors are stainless steel sleeved hence no rust. I beleive the accels are as well and I have no idea on the FIC injectors. I give you these three names as brandname options as folks have reported success with them but your mileage may vary. GC
GC

[secondchance]

How many miles on the Z and how often is it driven.

Without hearing the noise it is hard to troubleshoot. If the clutch disengages and engages properly, it is probably not the clutch or slave cylinder causing the noise.

The noise may be coming from the Dual Mass Flywheel. Usually the noise is caused by an engine miss that causes the engine rotation to be uneven and the flywheel noise results.

Since your ZR-1 is a 1990, if the injectors have never been replaced, that is most likely the cause of an engine miss. Original 1990 injectors eventually go bad when they are exposed to ethonol mixed fuels.

I replaced the injectors in four 1990 LT5's in the last year, and all 4 cars had three or more failed injectors.

Also, Check for good plugs, plug wires, and coils.

If you need someone to help investigate and repair your ZR-1, Rick (Rickyrj1) is about 1.5 hours from you and there is a lot of help available here in the Baltimore area (2-2,5 hours away).

Jim

I know it sounds strange but my 94 for years had similar noise. This noise would go away when the clutch was depressed. Motor seemed to run fine but had a faint pining I could hear at medium throttle around 1900 - 2200 rpm.
Eventually, as a last resort, I replaced all 16 injectors. Pinging was cured and hardly any noise from throw out bearing at idle.

[Duff]

Thanks again for the replies

After reading as much as I can on the subject, I'm pretty convinced it's the flywheel caused by the injectors, but the slave needs to be replaced anyway so I'm going to start there. I ordered a replacement today.

Tonight I'm going to run the car and really pay attention to when the noise first appears and if it's present when in neutral with clutch out or only when clutch is depressed. I'm also going to listen closely for a miss although, as I said, I really didn't notice a bad miss or major decline in performance (secondaries fire and no warnings).

I was hoping to wait until next winter for the plenum pull but if I can't, I can't.

[rkreigh]

the dual mass will get clunky if the car doesn't idle well, and it's common at shutdown as well

I messed up and got the spark plug well wet (yea don't ask) a long time ago and the car knocked so bad I thought I threw a rod

didn't like not running on all 8

the dual mass could be bad too, but it will bang around quite a bit if it's gone bad.

have a brutha give a listen! my bet is that the injectors are past their prime and you're hearing either the dual mass or some gear clatter from the ZF:confused:

[gbmidyear66]

My 90 did the same thing when I got it. No noise on cold start, but after it warmed up, at idle - it sounded like my turbo-diesel.

Yup, it was the injectors. What happens to the injectors is that the original design had the internal coils exposes to the fuel (I believe intended as a cooling mechanism). The ethanol in current fuels eats the coil winding coatings, causing parts of the coil windings to short, thus lowering the coil resistance. As the resitance degrades below about 9 ohms, the injector fails to function. When the engine (and injectors) heat up - this further reduces the coil resistance (Vs cold injector resistance) - this is why you notice the problem after warm up. You likely have one or more injectors "on the edge" the reduction in resistance after warm up is enough to push them into failure.

Get a handheld DVM and you can confirm the above diagnosis (you only need to check the primaries given it is an idle issue). There is a post on this board that explains the procedure

Talk to Jerry and get some plenum gaskets and Jon at FIC (he has about 3 products for you to choose from)

Glenn

Oh yeah - you might also want to call Haibek Automotive and get the plunum pull video.

[Duff]

My 90 did the same thing when I got it. No noise on cold start, but after it warmed up, at idle - it sounded like my turbo-diesel.

Yup, it was the injectors. What happens to the injectors is that the original design had the internal coils exposes to the fuel (I believe intended as a cooling mechanism). The ethanol in current fuels eats the coil winding coatings, causing parts of the coil windings to short, thus lowering the coil resistance. As the resitance degrades below about 9 ohms, the injector fails to function. When the engine (and injectors) heat up - this further reduces the coil resistance (Vs cold injector resistance) - this is why you notice the problem after warm up. You likely have one or more injectors "on the edge" the reduction in resistance after warm up is enough to push them into failure.

Get a handheld DVM and you can confirm the above diagnosis (you only need to check the primaries given it is an idle issue). There is a post on this board that explains the procedure

Talk to Jerry and get some plenum gaskets and Jon at FIC (he has about 3 products for you to choose from)

Glenn

Oh yeah - you might also want to call Haibek Automotive and get the plunum pull video.

I replicated my trip from the night before. Went for a 10 mile ride, as the car warmed up the noise got louder and more consistent. Also noticed a slight miss. Shutdown for a half hour and when I restarted the sound was very apparent.

I have the procedure for checking the injectors with plenum on. But, I probably won't get to it until the weekend. I have no doubt it's the injectors at this point. I'm still going to change the slave and bleed new fluid into the system as I know there is a slight leak.

I looked on the FIC website yesterday and plan on calling today. Is there any performance difference between the FIC rebuilt Bosch and the OEM replicas? I would like to stay as original looking as possible but if the Bosch perform better I may go with them and save $200. I'm probably going to go with headers and porting in the future (may now be my winter project) anyway as the longer I have the car the less I care about originality. In the end, the only thing that won't be reversible is the porting but you can't see that.

I have read a lot about the plenum pull and have the service manual as I planned on doing that anyway so I'm going to order the gaskets and have at it. I also bought a Haibek chip so I'll call Mark and get the video. Part of the reason I bought the car was to maintain and service it as a hobby and learn more about the mechanics so I'm kind of looking forward to it.

The information available hear is outstanding.

[Hammer]

Welcome aboard Duff.

I have the regular FIC's in my car, I think around $360 a set.

I just got back from BG and on that trip I averaged around 24-26 MPG at, oh, probably 75 to 80 MPH or so. I too had the knocking you are talking of before the injectors and it of course went away after installation.

GL

[QB93Z]

.......Part of the reason I bought the car was to maintain and service it as a hobby and learn more about the mechanics so I'm kind of looking forward to it.

The information available hear is outstanding.


Good attitude! :thumbsup: Plenum Pulling is the rite of passage of ZR-1 ownership. It is not really hard, just intimidating the first time.

Call he if you need a tech assist.

Jim
443-244-1347

[secondchance]

Good attitude! :thumbsup: Plenum Pulling is the rite of passage of ZR-1 ownership. It is not really hard, just intimidating the first time.

Call he if you need a tech assist.

Jim
443-244-1347

We've been under there so many times we can do it blindfolded, right?

Many of us have replaced injectors so if any question, there are plenty of us who can help on the forum.:thumbsup:

[gbmidyear66]

I bought the Multec "Look alikes" for $549 - I believe they are built in same SMP factory as the RC's, and are disc type.

I couldn't find a good reason to pay the xtra for teh RC's, and I didn't like the idea of "Rebuilt" in jectors (which as I understand is not even possible)

[Duff]

I bought the Multec "Look alikes" for $549 - I believe they are built in same SMP factory as the RC's, and are disc type.

I couldn't find a good reason to pay the xtra for teh RC's, and I didn't like the idea of "Rebuilt" in jectors (which as I understand is not even possible)

How long have you had them in and how are they working out? I like the idea of look alikes and, as I understand it, they are OK with the fuel additives. Also, they are ready to install. I'm torn between the FIC's and the Accels as recommended by M. Haibek. I know the Accels have a good track record.

[gbmidyear66]

Re Accell Vs the FIC "Multec Look alike". I could find nothing written to differentiate between the performance of these 2 products. I am happy with mine - idle is now very smooth @ hot and cold temps.

I think you are not down to the difference in $ and personal taste. I chose the look alikes to maintain a stock look (probably my latent NCRS tendencies)

[Duff]

Done!

Completed coolant system flush and refill last night and went for a test ride. She ran like a Swiss Watch. Un-friggin believable!

No rattle at all, the idle is smooth, the clutch is smooth, and the vacuum leak is completely gone.

Things I did:

Replaced clutch slave and fully bled system
Removed plenum, fuel rails, coil packs, Vac reservior, and secondary solenoid
Cleaned valley and everything in it - wasn't too bad
Tightened breather and intake housing bolts and breather hose clamps - loose
Tested vac system and installed zip ties on connections
Replaced secondary solenoid - source of vac leak
Replaced injectors with Accel injectors
Tested fuel system for leaks
Tested secondary solenoid and actuators
Replaced MAP tube - rotted at plenum barb
Put everything back together
Flushed cooling system and refilled with new coolant - no air lock

Thing is, it ran pretty good before (until the rattle), but not like it does now. It's like the car is saying AHHHHHHHH Thank You. I just didn't have anything to compare it to, but I do now.

Not that I'm breaking new ground here, but I absolutely enjoyed the whole process and learned a lot at the same time. I almost can't wait to get back in there.

Thanks again to those who offered their help, Mark H., ZFDoc, Jerry's gaskets and the unbelievable support for this car.

[Duff]

Dynomite,

I'm 99% sure it was one or more injectors failing that caused the noise. They tested OK cold but I'm sure they were failing hot. This has been discussed in may threads and documented by Mark H. among others.

And yes, forgot to mention I blew out the drain tube. Thanks for reminding me.

The other guys are the experts, I just consolidated the list. But looking back, if not already completed, I would recommend to everyone that the listed items be done as maintenance rather than out of necessity. No matter what the mileage is, they are mostly age related not wear related.

By the way, I can talk to a resource like Mark H. just by picking up the phone and Jerry at Jerry's gaskets hand writes an apology for not shipping the same day because he took a days vacation. How cool is that?

[secondchance]

I am glad to hear that you got everything sorted out.
I've been there. I know how it feels.:cheers:

[Belsy]

I know it is behind the successful discovery but my '90 had loose cat guts and it sounded like the clutch or engine had serious problems. Emptied cats and all was great!!

[Paul Workman]

Just got my engine back (gonna set it in the car this morning) after a bad exhaust valve was discovered.

It was the damnedest thing - looks like some metal on about 10mm long and 1-2 mm deep along the valve at the seat contact was, for better explanation, extracted! (The seat, except for some slight roughness your could just barely feel around the circumference, showed little damage to the naked eye.)

It is still unclear what may have cause the problem, since none of the other valves - even the other exhaust valve in that cylinder - were affected.

Conjecture at first was the engine ingested something. However, this was marginalized as there was not a single nick or scratch anywhere on the piston to support a foreign object loose in the cylinder. However, the machinist at AES suggests the valve surface was melted. And, after some cleanup and a closer look, he may be right.

What would the root cause be to affect just one valve on just one cylinder? Foreign object? Defective valve? Bob G (who has forgotten more about engine building than most of us will ever learn) suggests it might have been caused by a bad injector!! (Worth repeating)..."A bad injector"!

My point in all this is that the ramifications of a bad injector (or more) possibly extends to more than a little noise from the DM flywheel/trans, or a "little" power loss at throttle... Just something else to consider before shrugging and thinking, "Yeah, not too bad. I'll get around to changing them - maybe this winter!"

Just a thought.

P.



W

[tomtom72]

That is a fantastic bit of info to share with all of us Paul!:thumbsup:

Thank You .....from me any how.:worship:
I have to admit that I never thought about that consequence when my injectors failed.
I remember from the old days that if you put headers on a sb chevy you would lean out the back two cylinders on each bank & burn the valves because of a lean condition....but I never transferred that tid bit to an LT5! :o

Now I wonder how long it would take to do that type of damage to the valves?

Thanks man!
:cheers:
Tom

[Paul Workman]

I concur with this diagnosis :thumbsup:
I assume you are talking valve seat (on valve) rather than valve seat in head or are you talking valve seat in head (where valve comes in contact when closed with the head seat)?

Yep! The seat contact area of the valve itself (only) was involved. IF Pete hasn't pitched that valve in the trash, I'll try to post some pix of it.

BTW, the compression on all cylinders but #8 (with the bad valve) was 180#. On that one it was 100#. Al did a leak-down test, but I've slept since then and don't recall the specifics beyond a leak in the valve.

When I bought the car (from a dealer that specialized in Corvettes exclusively), he said the injectors were replaced at his request. He was a friend of mine, but I "ohmed" them out (hot) anyway, and they checked out.

But! From day one the song the starter made as the engine rolled over seemed to change pitch on one cylinder. I was a noob to the LT5 then (and pretty much still am a noob to the LT5) I asked about the change in pitch on this forum, but got no, zip, nada responses. So, I assumed it must be normal for an LT5 and thought no more about it. Later I noticed other LT5s cranking, and their starter song was monotone - apparently a good thing, and different from mine.

But, hell! The engine, bad valve and all, pulled 339 hp at the rear (stock) and I ran a 13.1 @ 111 mph on my first pull on the drag strip. Couldn't be anything wrong, right? But, once the compression check verified a bad cylinder, I noticed too that the starter's "song" variation coincided with the weak cylinder. So, I'm left wondering if the damage was done prior to my owning the car, keeping in mind the injectors were changed by the dealer prior to my buying the car - for "some reason".

Now, I'll tell you a little story on myself, if you promise not to tell anyone else.... What lead me to thinking a bad exhaust valve and the subsequent compression check in the first place was the "ticking" sound after I installed the SW headers. The cause of the "ticking" sound was a leak in a weld of mine coming from a hole in the header collector. The compression check coincidentally exposed the valve issue - pure dumb luck! :redface:
P.