Steven Haffley

I bought my first Corvette, a 1985 C4 4+3 that has 70k miles on it. I really like the car, it's like my gateway to see if I like it to maybe sell my g35 and buy a nicer and newer one. I bought it in June, it's going to be August and my mechanic has not been able to fix something I didn't think would be that big of a deal, the hydraulic clutch system.

The previous owner told me that the clutch was spongy. When I drove it, it was, but if I pumped the clutch I could shift. I bought the car and took it to my mechanic. The first time he replaced the slave cylinder and the actual clutch as he said it was getting worn. I got it back, it drove ok for 3 days, one day I went to my friends and came out to start it, and it'd lunge forward when trying to start as if I didn't press the clutch in at all.

Took it back to the mechanic a second time, this time I had him do the trick with the 2nd gear switch to turn it into a manual overdrive. He replaced the master cylinder this time and bled the clutch. He also said the clutch switch was going bad, so I had him bypass it. I Have an older 300zx turbo that has the same type of switch bypassed.

I just got the car back today, now it's next to impossible to put it into first gear with the engine running unless you pump the clutch. Sometimes when I shift from 2nd to 3rd it grinds, unless I pump the clutch. My reverse lights and side marker lights on the rear are on all the time when you turn on the car now as well.

I really want to drive this car, I bought it in June, it's going to be August and I still won't be able to drive it, has anyone had a similar problem with replacing all of these components, every single one of them in fact, and still have the same problem with the hydraulic clutches in these?

BLUDICE

find another mechanic

cv67

Did your clutch guy check the pilot bushing? Not saying thats your problem just curious. Id be parking that car on his doorstep and insisting he actually fixes it not just throwing parts at it on your dime that should have been checked before he gave it back!

Listing your area in your profile would help may be a member or better shop to take it to.

Steven Haffley

I just went out and checked under the hood and noticed the fluid was filled to the top of the cap rather than the "Full" line on the reservoir. I cleaned off (inside and out) a little pump I use to change transmission fluid and pumped out fluid until it was leveled off at the full mark.

I went back to test drive it, made a world of a difference though sometimes its a little resistant to get into first, however it is much easier. I also notice it is hardest to put in first when you stop the car with the transmission in neutral. If I leave the car in second when i'm coming to a stop it will shift into first very easily.

I'd work on this car myself and do these things but recently had surgery for thyroid cancer, makes certain angles you have to hold your neck while under a car much more agonizing but at some point I hope to be back to working on my own cars

I just updated this, good idea!

JimLentz

If you are at a stop and it hesitates to go into first put it in second and then back into first.

Raidmagic

I'd find a new mechanic. No way you should have received the car back if it wasn't right.

confab

It does sound like the master/slave because you can pump the clutch and it works. This indicates air or failing seals. I think he did right to replace them and it probably still has air trapped in it.

The clutch master cylinder is typically very small and doesn't displace a lot of fluid which can make it difficult to bleed.

If you drive it, it may work the air out without any intervention. If not, I bet bleeding it will fix it.

hcbph

I agree it sounds like you have air in the clutch hydraulics - been there, wrote the book. Right after I bought my 86, had the master and slave replaced and had much the same issues you are having.

My mechanic tried to bleed it many times with less than perfect results. Now I gave my mechanic the pages out of the FSM so he had everything there, but still it was the same: pump it up and worked but if you didn't it ground trying to get it into gear.

I looked on Youtube and found some videos on bleeding it. Tried them but none got the results I wanted (a clutch that worked without grinding going in and out of gear).

I lucked out, I found out a former co-worker was also a former GM mechanic and worked on these units. He gave me the trick that solved my issues. Take the cap off the clutch master and insure it's up to the mark. Engine off, pump the clutch like 10 times quickly and the last time hold the clutch down for about 5 minutes. At the end of the 5 minutes slide your foot off the clutch and let it pop up on it's own. If you have a lot of air in the system, you might have to do it a couple of times.

Premise is you pump the system up and hold it. Any air in the slave or line will work it's way up the like to the goose neck curve over top of the master cylinder. When you let the clutch pop up, the back pressure from the slave will push the air out of that curve back into the master cylinder.

I've been in your position, I did this and got immediate results. It's worked fine ever since on my 86. Try it, it won't cost you anything other than a little time and if your results are like mine, you'll enjoy the results.

Hope that helps. Good luck

Paul

OzyC4

I agree with the previous comments that your system hasn't been bled properly.
When I bought my 88 last year it drove perfectly, but somehow in the 3 months that it took to ship the car to Australia the fluid disappeared. When I picked the car up from the importer I had no working clutch, but his mechanic topped up the fluid and bled the system and it's worked well in the 6 months since that I've been driving the car.
I's not unusual that a manual gearbox occasionally won't go from neutral into first without selecting a higher gear first. I use third for this.

pologreen1

Take it to a real dealer or shop.

jv9999

Pump the clutch 100 times with the car off (seriously). More times than not, that will force the air out.

A C4 and paying a mechanic for everything is going to get expensive...

ElisTwoCents

This here

383vett

X2

Steven Haffley

I found a new mechanic, myself lol.

I bought a cheap $50 bleed kit for the brakes and used it for the clutch, it fixed it. It's the style where you use a vacuum to suck the air/fluid out instead of bleeding it the traditional way.

I still think there's something screwy wit the transmission but that's an entirely different thread I'm going to have to post because I don't think the hydraulics are causing it.

hcbph

I agree it's not the best design IMO. I figured if I ever have to redo this again I'd have a hydraulic shop make up a flex line to use in place of the oem one between the master and slave. My thinking is make a cradle that the slave would fit into, it would prevent the piston from blowing out the end of the cylinder while bleeding it. With the slave unmounted from the tranny, work it up so it's above the master cylinder. Put the slave in the cradle and should be able to be moved around so the air works up to the bleeder, now bleed it like a caliper.

There might be a better way but haven't thought of one yet. It sounds like your power bleeder did the job, if it worked then that's one to keep noted. Thanks for the info.

Steven Haffley

There's a cheapo $49.99 bleed kit at advance auto parts, the vacuum pump is metal, but the cup they give you to collect the fluid is junk. I used "the right stuff" and sealed the entire cup. It makes it so you can't unscrew it to dump it, but you can still dump the fluid out through the hoses. It was the only way to get a vacuum

Klondike

Difficulty getting into 1st gear at a stop from neutral can be a couple of things or a little of both. The 1st gear synchro gets a lot of abuse because it is the only one that has to completely stop the clutch disk from rotating when you are stopped to get the car into 1st. All the other gears are shifted into when the car is moving and only have to slow it down a little to match the gear speeds. When stopped, putting it into any other gear before 1st will help stop clutch disk rotation and make it easier for a worn 1st gear synchro to get it into 1st. Sounds like you might have a little bit of clutch drag and it's not fully releasing, causing the synchros to fight to stop the rotation of the disk. If the clutch disk is tight on the splines sometimes it sticks and still gets dragged around by the flywheel because it doesn't move away from the flywheel when the pressure plate moves away from clamping it to the flywheel. This happens a lot on replacement clutch disks if the splines are a little rough and dry. I like to file fit the disk splines to smooth them out so the disk moves freely back and forth on the transmission input splines and doesn't bind. A little graphite helps too, but never put grease in there cause it collects clutch dust and makes a sticky paste that will cause the disk to stick to the splines; Just the opposite of what you want. That disk has to 'free float' on the splines so the flywheel and pressure plate can rotate in front and behind the disk without either one dragging against it when you have the pedal depressed.

81c3

In addition to what Klondike suggests, I would say dump and fill the transmission fluid with new.... That can help synchro operation as well.