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Discussion Starter · #1 ·
So, after I changed my clutch (failed DMF. Changed with OEM GMPP clutch kit and OEM throwout/slave) at 105k miles, it drove fine when driving normally, and you could press the clutch at any speed, but if you released the clutch too fast, the clutch would stay disengaged (i.e. like it was pushed in, disconnecting the engine from trans) for 10-20 seconds until it slowly came back. I literally had to pull over on the side of 80mph interstate for this, a couple times, to let it come back. I eventually figured out that if you just tap the top of the pedal 2-3x, it would kick back at your foot each time, and I could get it to come back in 3-4 seconds like that.

Assuming fluid getting past the master cylinder and stopping it up, I changed the master cylinder. No change.

Because clutches in these cars, especially the first ones, are giant pieces of crap, the flywheels were on national backorder at the time, and I was able to find one of like 3 GMPP clutch kits in stock at dealers, and ended up getting one from the Caddy dealer in michigan who used to stock stuff for ZZP, who had 2. I bought the OEM slave cylinder at my local blossom Chevrolet in Indy. Now that I had replaced the MC, the only logical parts to be bad were the pressure plate or slave, both of which were new GM parts from the dealers. Well, Blossom says I've got to pay their service dept to troubleshoot and see if they're going to warranty the part that I bought from THEM. If they say it's the part I bought from the Caddy dealer, I still have to pay the unspecified troubleshooting fee (which could be up to and including them pulling the trans). Caddy dealer said they'd accept Blossom's troubleshooting and at least warranty the part for me, but they of course wouldn't comp the troubleshooting fee. I had to call GMCS to even get them on the same page, and for the dealer to agree to comp their troubleshooting if the part is bad. The moral of this story is, don't buy parts at the dealer for the warranty. The clutch parts all say LUK right on them, so just buy the LUK parts for 1/3 of the price and be done with it. Buy the OEM parts from Rockauto or something, and if you have a problem, just call them and say "the part is bad, send me another one" and then send your old one back.

Aaaanyway, Has to be one of the above parts, because I'd replaced all of the active parts in the system, and how could the facking hose possibly be bad, but not leaking fluid? Weeellll, ya see... Most mfgs who put in a clutch delay valve (CDV) do it like a check-ball system, where you can push the clutch fast and it disengages fast, but it flows slowly coming back up. In GM's infinite wisdom, their CDV is just a metered orifice (like a carb jet) inline that slows fluid both directions, and hidden under the coolant bottle, the hydraulic hose has this pressurized fluid reservoir that allows you to press the clutch fast without feeling the CDV stopping you. This is also the reason that this trans likes to start grinding gears when you shift fast... Because the clutch isn't fully disengaging, even though the clutch pedal is pressed. Well, it turned out that my clutch line reservoir (which I don't have apart yet, but I can only assume it's a pressurized diaphragm pushing back on the fluid, so it continues to push it through the CDV) did this cool thing where it didn't leak fluid when pushing on it, but when you release the clutch fast enough that the pedal spring pulls the pedal up faster than the clutch reengages, and there's a vacuum in the clutch line, it would suck air in right there, which would fill the top of the line and MC, and not allow the slave cylinder to send any more fluid up. The pedal kicking back at me when I pressed on the top of it was it bleeding off the air back up into the brake fluid reservoir. It did this with or without the CDV in there, BTW, just worse with it in there.

So anyway, changed out the $30 line/reservoir and it's good to go. I can side-step the clutch (obviously while in a gear, cruising, not tried while shifting) and it reengages nicely.


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Wow. How many weeks of troubleshooting labor would it have taken the dealer to figure that out if you'd given them the go-ahead?
 

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Discussion Starter · #4 ·
Cut it apart and it is an accumulator, exactly as I suspected. See attached. Straight-through line with, off the side of it, a stainless steel disk diaphragm, in a tapered cavity with a big spring under the middle of it, to add volume on the high pressure/master cylinder side of the metered orifice (clutch delay valve), so you can push the clutch pedal faster than the fluid can get through the CDV, without increased effort/resistance from the pedal.

Since it had been a question, to get rid of this action, one only needs to unscrew the center part of this (it does unscrew, with what looks like a 1" bolt's nut, with something welded to it to turn it), remove the spring and such, fill epoxy smooth/level under the stainless disk to get rid of the tapered area and spring center and fill it solid, maybe sand it smooth on something flat, then put the metal disk, the flat cut rubber ring, and the o-ring on it and screw it back in.

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