'97 Chev. K3500 clutch master / slave cylinders...

As many folks already know, the clutch master / slave cylinders used in the '97 Chev. K3500 and presumably other related models are essentially a defective design. The normal failure mode is a failure to release the clutch, the clutch itself doesn't seem to have any issues.

As the clutch master and slave cylinders have been replaced on my truck a couple times with OEM parts, and now they are showing signs of failing once again, does anyone know of good non OEM replacement components to use?

I'll be doing this next repair myself, and given that I have a fairly complete machine shop, I have no problem using completely different parts, even say Ford 350 series parts, and fabricating the appropriate adapters needed.

Thanks,

Pete C.

Can you tell how they are failing? Corrosion? Bore/piston wear?

Depending on the failure mode, you might want to take some of your "junk" parts and have them resleeved by someone like White Post, etc. will likely cost more than OEM parts, but also may last longer.

nate

I'm afraid I don't have any of my old parts readily available. My earliest set of pulls is rather far away from me at one of my other locations, and the most recent ones while closer were in a hurry and I didn't have time to think to keep them.

The last failure was the slave cylinder, but it was a clear case of seal failure as it was leaking a fair amount of fluid. This time it seems more like the master cylinder as there is no evidence of fluid loss, and the no-release condition clears with some pumping.

If I'm digging into this myself this time I'd like to replace with better non-OEM parts and be done with it. Adapting a different MC would be easy enough if I can figure out which MC would be the best replacement.

I see that they seem to have changed both the MC and slave cyl. in 2001, but I'm not sure what else they changed.

The seal fails when the rubber goes bad, and the seal fails when the wall becomes pitted or rough or was badly machined and tears the rubber up. Or sometimes the machining is so bad it just can't make a good seal.

If the walls are fine and the bore is actually round, you might be able to easily replace the seals with better quality ones and be fine. Or maybe not. You need a postmortem to know.

--scott

Perhaps, but I've had the impression based on 208k+ miles with this truck, that the master cylinder displacement is really a bit too small. I'd like to find a MC with a little more displacement and without a know track record of failures. I don't care if I have to fabricate a mounting adapter and hydraulic adapter to get it installed, I just want this to be the last time I f' with it.

Replaced POS MC this afternoon with another POS MC since I had to replace it before I had time to find a better part. Autopsy results to follow...

I like afco master cylinders. Get any size you want.

It seems unlikely that both parts failed at the same time. You should spend some time diagnosing the problem and then repair it. Since you a wiz at fabrication why not fabricate a new truck and then put the Ford parts on it.

nobody #1 dumb answers for dumb questions at your service

Ok, now I'm really pissed off. I replaced the MC and things seemed to be ok for 30 min or so, then the problem returned, actually worse. WTF?

Air getting into the system somewhere OTHER than the cylinder seals? Like maybe a bad line?

--scott

Dunno, the quick connect perhaps? I'm not sure it's an air issue however, since it doesn't really feel "spongy". It is really difficult to try to bleed it solo, also difficult to tell if there is air coming out when bleeding due to the long bleed screw from the coaxial slave cylinder.

I just went through this on my Porsche 944; the hose connecting the master and slave blew on me one morning (fortunately while the car was parked in front of my house.) I limped it down to the corner garage where I had the guy replace the whole shooting match (master, hose, and slave,) since there's so much labor involved just getting to the stuff compared to the price of the parts. He couldn't get a good pedal on it, I couldn't either, until a more Porsche-savvy friend told me "the trick"

- hook up a pressure bleeder to the reservoir, pump it up, bleed as normal, close bleed screw (there's only one, on the slave - WTF?) then get in the car and pump the pedal quickly 20-30 times, get under the car as quick as you can and open the bleeder again. repeat the last step again and all the air is out.

Dunno if this is applicable to your situation or not...

nate

Hey Nobody........you are out of the box again ! haw haw haw Pete

Possibly, the service manual does list two different bleeding techniques, with one to try if the first doesn't work. They don't mention a pressure bleeder however.

It doesn't appear to be an air issue however, as last night I couldn't get the clutch to disengage no matter what I did, and this morning it's working again.

Hmmmm......I've got a '96 Silverado 305, 5spd, that just turned 160k. I still have the original clutch and master/slave cylinders. Never had a moment's problem in that area.