Help! c4 hydraulic clutch problem!

[H.H. McCool]

hello to the group from a new member,
i recently purchased a '94 LT1 coupe w/manual transmission. over the last six months, the hydraulic clutch slave cylinder has cracked and had to be replaced three times. this car has a custom exhaust system, true dual exhaust, no resonater, two standard type cats. i do not know the brand. the left cat is approximately 2-2.5 inches away from the cylinder. the mechanic at the chevy place suggested that the heat from the cat might be causing the plastic cylinder to crack, so i had a heat shield installed over the cat. the cylinder cracked again. the cat is also only an inch or so away from the oil filter, and it seems to me that if there were a real heat problem, it would effect my oil temperature and pressure. both are normal- 55-60 lbs of pressure, 215 degrees when warmed up.

has anyone had such a problem or have any ideas as to how it might be alleviated. i could really use some help on this perplexing problem. thanks for any input that is provided.

 

[lone73]

Plastic??

hello to the group from a new member,
i recently purchased a '94 LT1 coupe w/manual transmission. over the last six months, the hydraulic clutch slave cylinder has cracked and had to be replaced three times....
.... causing the plastic cylinder to crack, so i had a heat shield installed over the cat. the cylinder cracked again. .

Your slave is plastic?? I just put a new clutch and aluminum F/W in my '96, 6-speed and I am next to positive it was steel. Could be wrong though. You may want to try an OEM style for a '96.

I have had clutch master/slave woes in the recent past too. I put a slave on at 70K that LOOKED like an OEM slave but the brand was different. Seemed to work fine. Then At 100K I put in the new F/W and disk and a new O'Reilly's brand master (lifetime warranty). These two parts have failed on me in the past and left me on the side of the road in other types of vehicles so I didn't want to take any chances with the vette. I then started having lots of problems with air in the system. Then the fluid level started dropping and leaking out the slave really bad. I eventually put the original master AND slave back on the car to get it to work again. That was 10K miles ago and absoultely no prob's since. So now I'm back where I started.

I have swapped out the warranted master but haven't had the courage or time to try it out. I should mention that the original master cylinder is a smooth black painted steel looking piece w/plastic reservoire. The one from O-Reilly's is a cast part and much heavier and bulky. Had trouble getting it in the hole.

The heat shield sounds like a good idea.

Oh yeah, Welcome to CAC...
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[c4cruiser]

The clutch slave cylinder is supposed to be aluminum, not plastic. A heat shield is the best way to go but I don't think that the factory exhaust had a heat shield in that area. Even the rubber dust sheild is not normally affected by exhaust heat!!Your oil temps sound about right but I don't think that the cat in the OEM location would have a major impact on oil temps. It should be easy to fabricate a small heat shiled to protect the slave cylinder, but the best way is to use an OEM or equal part. It should be a aluminum body.

 

[froggy47]

I just replaced the slave on my 96 & it's not plastic. Got oem from Chev Dealer:confused

 

[H.H. McCool]

froggy47, if the part you are referring to is gm part # 12509313, it is constructed of "injection molded plastic." so far, i have had two installed by my local chevy dealer, newton chevrolet, and both have cracked within 90 days. i have investigated several other suppliers and their's are plastic, too. i went to a local race engine building company and asked them for help. they also said that all the ones they could find were plastic. if you have a part number, please pass it along to me. i would really appreciate it. thanks for the post. -HHM-

 

[-=Iron Mike=-]

I've had to replace two since last Febuary. My leak was coming from the rubber boot seal. They were direct from GM (I'll check the part # when I get home if it will help you) They are painted black and what apears to be aluminum. Plastic just doesn't seem right.

 

[froggy47]

froggy47, if the part you are referring to is gm part # 12509313, it is constructed of "injection molded plastic." so far, i have had two installed by my local chevy dealer, newton chevrolet, and both have cracked within 90 days. i have investigated several other suppliers and their's are plastic, too. i went to a local race engine building company and asked them for help. they also said that all the ones they could find were plastic. if you have a part number, please pass it along to me. i would really appreciate it. thanks for the post. -HHM-

I took a knife to the old one & scraped thru the plastic/paint coating so you can see the metal. The new one is the same - it's too heavy to be plastic - the part # is the same. See the little shiny spot - that's the metal & I don't think it's aluminum as the knife blade does not go into it like it would aluminum - if you know what I mean.

I got mine from Chris at Superior - great guy & great company to do business with - shipping not too bad.

When I was bench bleeding the slave I did notice a little rust spot inside the top connection - where the line from the master attaches. I suspect that these oem slaves have been sitting in inventory for a while - somewhere. This could explain why some guys have to replace them more often than you would think necessary. Let's say there is a rusty spot in the bore - it'll wear out the seal part faster than on the original brand newly mfg. part. Just my guess.