Clutch, grinding noise when fully depressed.

[luvlar]

Greetings to all my fellow corvette enthusiasts, This is a great forum and I've found answers here many times in the past. I've never posted anything before since I'm no mechanic, back yard or other wise. I only drive em, don't know what makes em' go. My question to all you with the know how and knowledge is this, About two weeks ago I was having trouble shifting between gears. Really had to push or pull hard. Checked the trans fluid level at the reservoir on the fire wall and it was way low. Way, way low. Filled it with GM syncromesh and bought a new diaphragm since the old diaphragm was fully extended and I couldn't "squish" it back to flat. Filling the fluid fixed the problem and everything was fine. I've noticed a small leak when I squeeze under the car and look at the trans. Nothing serious. Several weeks passed and the fluid level hasn't dropped. About two weeks later I'm now getting a grinding noise when the clutch is depressed fully to the floor. Doesn't do it at 1/2 or 3/4 pressed. I can shift gears just fine at the 1/2 or 3/4 mark but need the clutch just about fully depressed to start it. That's when I hear the grinding. It drives and shifts perfectly, smooth and tight, but put the pedal on the floor and it sounds like metal grinding. Kind of like worn brake pads sound. I'd appreciate any feedback you can give me. 1994 with 18000 original miles, Thanks! Regards, Frank

 

[93Rubie]

Ok, first off that reservoir on the firewall is NOT for transmission fluid. That is the master cylinder for the clutch it takes DOT3 Brake fluid ONLY. I suspect your slave cylinder is the leak, that is located in the bell housing next to the transmission on the drivers side. The grinding could be many things at this point. I suspect the slave cylinder being bad has something to do with it.

At this point your going to need to have someone look at the car. If I where you I would consider replacing both the master cylinder and slave cylinder seeing as you have contaminated the system with a foreign fluid. That and if one is bad the other cannot be too far behind.

Another thing, you SHOULD be pushing the clutch pedal the entire way to the floor when starting and when shifting. Doing any thing less like 1/2,3/4 is shallow shifting and is death to a transmission, not to mention your clutch. Without actually hearing it or being there I cannot even give a reasonable guess on what the grinding noise might be...it could be the throw out bearing but since it does not do it with the clutch pedal pressed in even 3/4 of the way....maybe not. I would want to get the clutch hydraulics taken care of first, then worry about the noise. They maybe the same problem, the leak could have led to the noise occurring???

In the future please refer to your owner's manual before adding any fluids. It may save you a headache.

 

[Hib Halverson]

As "93Rubie" suggests, you put trans lube in the clutch master cylinder reserviour and that fluid will destroy both the master cylinder and the clutch slave so you're looking at a repair job just to replace those two items and probably the hydraulic hoses between the two.

Plus, it sounds like you have a problem with either your clutch, the clutch disc or the release bearing.

My strong suggestion is you discontinue trying to fix the problem yourself and seek the assistance of a service shop specializing in C4 Corvettes.

 

[smokestack]

Great advice so far. Like normal around here

kinda off topic but coildnt they just flush the system? Then fill it with the right fluid? I have no idea. Thats why i asked here

 

[luvlar]

Thank you all for the advice. If the forum has a knucklehead of the year award I humbley accept your nominations. :eyerole On the bright side the slave had a leak anyway so replacing it was on the list. Funny though, I told the guy at the GM parts counter exactly what my problem was and what I was doing and he said the GM Syncromesh for manual transmissions was considered to be good stuff. Maybe we also have a runner up for knucklehead of the year?

 

[luvlar]

Great advice so far. Like normal around here

kinda off topic but coildnt they just flush the system? Then fill it with the right fluid? I have no idea. Thats why i asked here

I was wondering that too. I've put maybe 50 miles on the car since I goofed. Would that much damage occur with such little driving time???

 

[Hib Halverson]

Great advice so far. Like normal around here

kinda off topic but coildnt they just flush the system? Then fill it with the right fluid? I have no idea. Thats why i asked here

Good question...I should have explained in my previous post.

Petroleum-based products (ie: transmission lube, engine oil, etc) contain substances which are solvents for the rubber parts in the hydraulic clutch cylinders. Also, in the case of clutch masters and slaves linked by rubber hoses, petro-based products may damage the inside of the hoses.

Once petroleum substances are introduced into the hyd clutch system the internal parts are toast. In the case of C4 Corvettes, because the master and slave are not rebuildable, you have to replace all the parts.

Now...
(sigh)
...with respect to the OP. I've read it a couple of times. I'm going to guess that the original problem with high shift effort was caused by the clutch dragging or not releasing fully. If the clutch fluid was really low, there was probably insuffiient fluid and air in the system. The leak which has developed is probably because the seals in the slave are self-destructing.

As for the "grinding" noise you hear when the clutch pedal nears the floor...do you hear it whether the engine is running or not or only when the engine is running?

 

[luvlar]

Good question...I should have explained in my previous post.

Petroleum-based products (ie: transmission lube, engine oil, etc) contain substances which are solvents for the rubber parts in the hydraulic clutch cylinders. Also, in the case of clutch masters and slaves linked by rubber hoses, petro-based products may damage the inside of the hoses.

Once petroleum substances are introduced into the hyd clutch system the internal parts are toast. In the case of C4 Corvettes, because the master and slave are not rebuildable, you have to replace all the parts.

Now...
(sigh)
...with respect to the OP. I've read it a couple of times. I'm going to guess that the original problem with high shift effort was caused by the clutch dragging or not releasing fully. If the clutch fluid was really low, there was probably insuffiient fluid and air in the system. The leak which has developed is probably because the seals in the slave are self-destructing.

As for the "grinding" noise you hear when the clutch pedal nears the floor...do you hear it whether the engine is running or not or only when the engine is running?

Thank you again for your feedback. Regarding the OP, when I was having trouble shifting between gears I checked the fluid level at the reservior and it was way low. Hardly any fluid visible. So insufficent fluid and air in the system would be absolutely correct. Adding the fluid corrected the problem. Shifting return to smooth, tight and normal. Little did I know then that I was using the wrong fluid.

I can only hear the grinding noise when the car is running. Push the clutch to the floor and it sounds like bad brake pads might. Metal grinding on metal. No noise when the car is off, no noise at 1/2 or 3/4 pedal while car is running.

What if I flushed out the fluid I put in and add the correct Dot 3 brake fluid? I've found several ways to do that on line. Keep cycling out the fluid at the reservoir, turkey baster - remove fluid - add new - pump clutch 30 to 40 times - repeat. OR, bleed it out under the car with the bleeder screw until only new fluid is seen.

Or do you think it's too late for that? The damge is done.

 

[BigJimZ16]

Bottom line is that you need to change one of the components anyhow... you have a leak! The clutch master cyinder wasn't low on fluid from evaporation... You NEED to at a minimum replace the leaking part and SHOULD replace the rest.

 

[luvlar]

Bottom line is that you need to change one of the components anyhow... you have a leak! The clutch master cyinder wasn't low on fluid from evaporation... You NEED to at a minimum replace the leaking part and SHOULD replace the rest.

That's definetly the correct answer. I knew replacing the slave, etc. was where I was heading but I was hoping there'd be an easy fix. The leaks got me confused though. I never saw puddles on the grage floor and still don't. The fluid level hasn't changed since I topped off. I don't see a leak anywhere underneath. Got me stumped.
What I really wanted to do was stop the noise so I could trade it in on one of the 08s a local dealer has on his lot. And be able to fix the problem the cheapest way possible since it's a trade in. Freind of mine wanted to buy it but I told him to pass. Wouldn't sell it to a buddy now that I know there's clutch problems.

Looks like I'm up the creek and need to talk with a mechanic. Thanks again.

 

[John Robinson]

Welll you could always quickly drum up a deal on one of those 08's without doing anything. It's called dealer beware. Seriously look at what the car is worth as is on a trade then factor in what it would be worth if it were fixed. Don't forget to deduct what you would spend for the repairs from the extra you might get fixed over not fixed on trade. My guess is you might break even but I don't think in the long run you will make enough more to be worth the trouble of having it fixed before trade.

 

[luvlar]

Welll you could always quickly drum up a deal on one of those 08's without doing anything. It's called dealer beware. Seriously look at what the car is worth as is on a trade then factor in what it would be worth if it were fixed. Don't forget to deduct what you would spend for the repairs from the extra you might get fixed over not fixed on trade. My guess is you might break even but I don't think in the long run you will make enough more to be worth the trouble of having it fixed before trade.

That's my delema. To fix or not to fix. I think a dealer would run scared if he heard the clutch noise. Honestly, my choice would be to go with dealer beware if I could stop the grinding noise when the clutch is put to the floor. Call it payback for the times I got screwed when I was younger and buying me first used cars. Wouldn't do it to a private buyer though.

 

[John Robinson]

So your concern is what would happen if the dealer drove your car in order to figure out what it is worth on the trade. I don't know about were you are but the last time I had a dealer test drive my car to determine it's value I was in knickers. Whats the worst thing that could happen they offer you less because of the noise. There is no embarrassment in telling them their deal is not good enough and then get up and walk out. I would bet if you did get up and walk on a deal in progress they would be on the phone with you within an hour with a new proposal.

 

[luvlar]

So your concern is what would happen if the dealer drove your car in order to figure out what it is worth on the trade. I don't know about were you are but the last time I had a dealer test drive my car to determine it's value I was in knickers. Whats the worst thing that could happen they offer you less because of the noise. There is no embarrassment in telling them their deal is not good enough and then get up and walk out. I would bet if you did get up and walk on a deal in progress they would be on the phone with you within an hour with a new proposal.

Good point. I'm sure they don't execute people who turn down trade in offers. If I had to guess, I'd say they'll knock of 2 grand from trade in value. Maybe a little less but if I were working the deal from the other side I'd play it safe and figure the whole clutch may need to be replaced. From what I've seen on line that can be anywhere from $1600 to just over $2000.