THE CLUTCH ON MY 96 C-4 (LT4) IS KILLING ME ; I CANNOT GET INTO OR SHIFT GEARS WHEN NOT ROLLING AND WHEN I COME TO A STOP WITH THE CLUTCH PEDAL FULLY DEPRESSED THE ENGINE BOGS DOWN AND DIES; THE CLUTCH IS NOT FULLY DISENGAGING (OR IS NOT FULLY ENGAGING...NOT SURE WHICH IS THE PROPER TERM?) THE FLUID LEVEL IN THE MASTER CYLINDER IS FULL BUT THE FLUID WAS VERY DIRTY/DARK. COULD AIR IN THE SYSTEM CAUSE MY PROBLEMS? THE CLUTCH WAS REPLACED WITHIN THE LAST 15k MILES. ALSO, THE CAR RUNS AND SHIFTS WELL ONCE AWAY FROM A DEAD STOP BUT I CAN ONLY GET THE CAR INTO GEAR WITH THE ENGINE OFF; TO GET IT A SHORT DISTANCE HOME I HAD TO SHUT IT DOWN TO STOP AND THEN RE-START IT WITH THE TRANSMISSION IN GEAR. WHAT SHOULD I LOOK AT WHEN I GET UNDER THE CAR; WHAT'S MY NEXT MOVE? ANY ADVICE APPRECIATED.

 

Your clutch is engaged all the time, that is why you cannot get it in gear when stopped. You might have air in the sytem, but definetely dark fluid is a sign of water that has caused corrosion which has discolored the fluid. At least annually, you should replace clutch and brake fluid to get rid of water that gets into the fluid.
You can try to bleed the clutch slave and see if that helps.

 

There is probably a leak inside the clutch master cylinder. Do a search and there is a lot of info on changing them out. It is not too expensive.

Here is some other good info too.
http://www.zfdoc.com/

 

First of all, stop driving the car until this is fixed as you are doing severe damage to the internal components of the transmission by shifting without the clutch properly 'disengaging'.

Whereas the color indicates dirty fluid and possibly contamination, since the level is NOT low, at least a bad leak can be ruled out.

Suggest getting under the car (roughly right below where your feet usually are) and use your fingers to feel if when the clutch pedal is depressed (you'll need a 'helper'), if the clutch fork is being depressed.

The clutch fork is inside the bell-housing and is pushed-forward by the shaft of the clutch-slave-cylinder, which is mounted to the bell-housing and has a stainless-steel braided hose attached to its rearward end with a bleeder-screw facing downward (hopefully with its rubber cap still intact). By inserting a finger in/around the slave cylinder's nose, you should be able to feel the fork move, or perhaps at least see it move if you can use a mirror and some light.

If the clutch fork is moving, this suggests that both the clutch-master and clutch-slave-cylinder are working, albeit not yet sure they are working to their full potential.

To bleed properly, have the butt of the car higher than the front (use jacks and jack stands -- remember safety first )..

The next thing to try would be to bleed the slave (and thereby the master) by sucking out most of the brake fluidas from the master (leave just a bit in the bottom to keep it from going dry) and refill just to the line with fresh brake fluid (suggest either GM's clutch fluid or a good quality DOT-3 brake fluid (NOT DOT-4 or DOT-3 compatible) and reinstall the rubber bladder and cap. Then go below and bleed the slave (just like doing brakes, press pedal, hold, open bleeder a bit, close, slowly up on pedal, pause, repeat).

If you get air from the bleeder (good to put a clear hose on the bleeder to be able to see this), then this might solve the problem as the air was compressing and not transmitting all the fluid to the slave.

Once done bleeding, suggest then without the car running, depress the pedal to the floor and up again slowly and fast 20-30 times (it pulls any remaining air up to the master). Then check the fluid level, top off and cap.

Then put tranny in neutral, start the car and see if you can put the car in gear when the clutch pedal is depressed (clutch dis-engaged).

If so, problem solved. If not, then either the master (or slave) are not operating correctly, or there is a problem with the clutch or clutch-fork.

Replacing the slave is not difficult and frequently they die around 50k miles, so if adept, could try and replace it (GM/NAPA are having problems in QA, so suggest PBR brand, can be found at partsgeek.coml or some local shops).

at this point, might want to get it back (suggest towing) to the shop which did the clutch and having them (or another shop) 'fix' the problem.

 

THANKS EVERYONE THE CAR IS UP ON STANDS AND TOMORROW MORNING I'M GOING IN...

BY THE WAY, I DROVE THE CAR ABOUT 2 MILES WHEN THE PROBLEM OCCURRED AND HAVEN'T DRIVEN IT SINCE. COULD NOT LEAVE IT WHERE IT WAS...AND STILL HAVE IT LATER.

THANKS AGAIN!

 

Not trying to be a butthole, but try to find the Caps lock on your keyboard.

The characteristics you describe are most likely a Clutch m/c or slave going bad. theadmiral pretty much laid it out for you.

 

Well, got under the car today and noted the following:

1. no noticeable leaks around lines or slave cylinder
2. dust cap missing from bleeder (will replace)
3. could not find an angle to check whether clutch fork is being depressed; either by finger touch or with mirror and light.

Bled the brakes as instructed but noticed no appreciable amount of air leaving the system. Checked fluid (still full)

After bleeding I slowly pumped the pedal 30 times. Effort needed to push down the clutch went from nearly limp to what felt like normal at the end of 30 pumps. Fluid level in master was still full; reinstalled the bladder and cap.

Took the car off stands, put shifter in neutral and tried all gear shift combinations with engine off. No problems.

Turned engine on; went from neutral to first gear smoothly; same with reverse. Backed the car into the street and started out in first gear with no noticeable problem. Subsequent shifts up to fourth - likewise.

However, shifting then began to be more difficult (notchy, more effort required. After total driving distance of 4-5 blocks arrived back in my driveway, put shifter in neutral and could not get back into gear with motor running. Checked fluid (still full) and checked under car for leaks (none). After the car sat for a minute I was able to again get into gear from neutral (with engine running) and put 'er back in the garage.

Since I get normal shifter motion and clean shifts at first it seems to me that the clutch and fork are operating properly and that it is a fluid problem involving the slave or master cylinders. Since I cannot detect any leakage should I start with replacing the slave first? Thanks for any additional help...

 

KSTRDAN,

Nice job on analysis and write-up... (got your PM, your welcome)..

Agreed -- clutch and fork are fine, since it shifted great for at least a few minutes...

I was ready to say 'bad clutch-slave', If it weren't for the "sat for a minute I was able to again get into gear" comment -- now I would say it might be both clutch-slave and clutch-Master. I wonder if the clutch-master's seals are failing and 'rest' gives the seals a chance to re-seat and push fluid again.

The "went from limp to normal" could be either air (e.g. in the slave being sucked-in through the seal from the front/clutch side) or the clutch-master seals failing but frequent movement helping to expand the seals just enough to start pumping fluid again.

So, I concur with your thoughts -- start by changing the clutch-slave as it's the easiest of the two (remember to try the PBR brand, e.g. local parts house or partsgeek.com -- that's the one I'll be getting for my new one in a week or so).

you will need 'line' wrenches to keep from rounding or collapsing the line connectors (remember a vise grip can be used if the 'line' wrench starts to spread).

Suggest un-tighten the hose from the slave 'before' unbolting the slave . Once disconnected, it will drain the master unless you cap the hose (maybe a valve cap or that new bleeder cap which should come with the new slave.

ONLY Gravity bleed the slave before full install into bell-housing (loosen bleeder, connect hose, top off master, with slave 'butt' held upward -- be careful, do not bend/kink the hose -- open bleeder until only fluid comes out (watch master doesn't go dry). DO NOT pressure bleed (i.e. pump clutch pedal) until FULLY installed as it WILL damage the slave.

Remember after install and standard bleeding (slowly down, hold, open/close bleeder, up slowly, repeat) also do 30-50 (more since it's new) slow-fast-slow pumps of the pedal after bleeding, to 'finish' the job.

Hopefully this will do it, but if not, then its to the clutch-master -- not sure on brand (if PBR makes one, get it, as there are reports of problems with GM and NAPA brands -- mine is a GM and I 'think' it's still ok after 2004 install, but one never knows for sure).

Clutch-master isn't too bad -- I didn't, but hear removal of the driver seat can make getting the pedal connection easy (only 4 bolts and a few plugs, mark plugs as two are the same). I also replaced the line at the same time, so I don't remember how/where I disconnected/reconnected (in place or at bench before dropping hose downward). However, I do remember you must tighten the hose to the master before installing master and hose's mid-length bolt, otherwise the flare of the pipe will not set right at the master and it will leak (yup, found out the hard-way).