My work truck, a 1994 Chevy C2500 Turbo Diesel, has been giving me problems with blowing out the clutch hydraulic master cylinder. Have gone through about ten of them and even replaced the clutch about five cylinders ago to no avail.
My question is as to what the housing of the clutch master cylinder is made. It is some type of black polymer. If I can identify the type of polymer, I am hoping to reinforce the area that keeps blowing out.
Replies
Where is the blow out? Could it be over travel pocking a hole in the end? What type of fluid are you using? Maybe an earlier cylinder will be made of metal instead, but will it fit?
If'n ah had one of them polymore clutch cylinders after dat many blowouts, sure would go out back an' slavage a cast arn one off'n a 64 Chev or sumptin' - 'lessen it still under waranty?
gone through about ten of them -- WOW, gald ah dont have ona dem!
If it dont crack whenya bash da ol' one wit a sledge, probably polycarbonate.
If you do not want to go the cast iron (or aluminum) replacement, wrapping it in fiberglass tape and epoxy is one thing to try.
Hell, if he went thru that many there should be a recycle symbol on em..Spheramid Enterprises Architectural Woodworks
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I think Sphere wins the prize: Look for the recycle symbol. Otherwise you need to try various solvents to see which one works.
try various solvents to see which one works
Ya got a list of solvents vs. polymer type and reactions?
Heck, try MCl on it, then you will know it's a plastic, that stuff will even eat TFE over time and temp.
Would like to see a good complete list 'cause I don't know of any open source list, other than the obvious PVC vs. MEK, acrylics and methCl, etc. There are some proprietary lists I've seen, but you would need a chem lab to have access to some of the test chem.
One open source net list is
http://www.carlislesmp.com/solutioncenter/solventguide.pdf
I think the clutch is bad. Binding up and needing too much pressure, or it's an extra heavy unit with too high spring pressure. Could be a restriction in the hydraulic line or a sticking slave cyl also.
The clutch that was in the truck when I got it and the replacement clutch both blew the cylinder at about the same rate. The Clutch Doctor place that did the the replacement swore that it was an OEM clutch and would be soft - year, right. I am planning on replacing the pressure plate once again (after about 40K on the current one) as soon as I can find a space suitable for dropping the tranny; however, I can't find info on which pressure plates are soft. I replaced the master, slave, and hydraulic line all at the same time and it didn't help. The crack appears to be (at least for this latest one) at a narrowed area jut above where the hydraulic line attaches. Probably the cylinder is a marginal design that works with the factory setup but blows out when there is just slightly more resistance with a replacement setup. (The factory flywheel is a dual mass which most people seem to replace with a solid flywheel when the dual mass flywheel inevitably goes out). I am not aware of a metal cylinder that will work. Earlier Chevy trucks used a mechanical linkage, not sure when they changed. Have gone through several wrecking yards but none of their Chevy trucks had manual trannys.Maybe this type of problem is why GM no long offers manual transmissions on their 3/4 ton trucks, among others... Oh, the polymer is a dull black. I found that epoxy sticks to it so packed some JB Weld around the narrowed area to try and give it a little added strength. I doubt that the epoxy adheres all that well, but hopefully well enough to give me a few more miles before I have to swap out the clutch. Other than the clutch, the truck runs well for 307,000 miles. I woul like to upgrade to a later truck, but even early Duramax pickups are listed for nearly $30K. I thought with high fuel prices pickup prices were supposed to have dropped, but that appears not to be the case with diesels.
Consider that vibrations or pulsing motion in the hydraulic line may be fatiguing the plastic.
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Only one last idea. Could overtorquing the line to the cylinder be a factor?
The line is held in by a roll pin, no adjustments allowed.
Take a look at the engine mount condition. Excessive pulling/pushing on the hyd line will crack the clutch mc housing. Is the line attached to the firewall after it comes out of the mc? That would help as a strain relief so no tension is applied to the mc and fitting.
Does the clutch pedal pulsate or feel hard overall? If so, I'd also suspect either a warped fw(dm's are junk to begin with), or a restricted line, respectively. To be honest though, that would have to be one hell of a restricted line and hard pedal to overpressure the mc.
The seals inside the mc and slave would leak a long time before excess pressure would crack the housing. I'm clearly leaning towards a vibration/physical stress issue.
Definitely lose the dual mass fw, either way.
EDIT: This was not a frequently encountered problem. Injector pumps and dm fws, all day long, but hyd clutch issues? Very rare IIRC.
Edited 9/23/2008 11:05 pm ET by deadman1
The hydraulic line is secured to the bell housing and then has a couple of bends before it gets to the master cylinder. The last foot or so of the line appears to be either plastic tubing or metal encased in plastic. The section closest to the slave cylinder is metal. The engine does not rock excessively at idle, but I haven't checked the motor mounts. I used a hose clamp to sort of secure the line to the master cylinder one time and it didn't seem to improve the situation. I want to remove the bell housing. I dropped the tranny a couple of years ago and found that the engine didn't drop down far enough for me to get my hand in between the bell housing and firewall to allow me to remove the top bolt. Is there an easy way to get the engine dropped down to get access to all the bolt? (This is a 1994 6.5L turbo diesel)Thanks
No, take it out before you try to drop the trans.
If I absolutely can't get at it from the top, I use a special bellhousing extension...it's about 3' long, 1/2" female for the breaker/impact gun, and 3/8" male for the swivel socket.
I absolutely take the top 2-3 bolts(depends on bell style) out before even going under the truck, when I can. Occasionally there'll be a turbo crossover pipe or something in the way(depends on year/model etc, but 9 out of 10...from the top.
Sometimes it's even easier to pull the obstruction than fight with it from underneath.
If the mounts are worn, it wouldn't really rock at idle. And prying it around to test movement is not as easy with a 1,000# diesel as with a 500# gas motor.
Open the hood, and get in. Plant the parking brake and rev it up and slip the clutch, see how much it moves. the Driver's side valve cover shouldn't rise more than maybe 1". The exact amount of movement isn't that relevant(.25 vs .5 vs .75"), if the mounts are worn out, the engine will jump up under load. If they're tight, it'll smoothly rise.
You'll see what I mean. It'll just look sloppy if they're worn/blown.