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Clutch Master Cylinder Pushrod Keeps Bending During Bleed!

13K views 9 replies 7 participants last post by  nvrenuf 
#1 ·
This is my first thread and post. I'm having a horrible time trying to bleed my clutch! I did a search but could not find anything to help me out. I just got an '87 K30 454TBI with a bad body that I am transferring my nice '83 C20 body onto and in the meantime, i am having some trouble. I was driving the truck around and noticed that everytime I got to put it in 1st or reverse, the SM465 grinds like crazy and is very hard to get into gear sometimes (and i would have to smash the pedal to the floor with incredible force)! This had happened on my C20 as well (the grinding every now and again, but not hard to get in gear) but not nearly as bad as this one. The K30 has a the hydraulic clutch setup. Well, i took off the slave cylinder, and used a bleeding kit (vacuum that pulls on the bleeder valve to draw the fluid through) and no fluid would come out of the valve. So after a little more trial and error i came to the conclusion that the master cylinder was the problem.

I bought the new master cylinder, hooked it up, and then hooked up the slave cylinder instead of using the bleeding kit since it is a self-bleeding system anyway. I pumped away at the clutch a 2-300 times until it built up pressure, and then one time i pushed the clutch in and then the pedal never came back out! I looked underneath and the pushrod between the clutch pedal and the master bent! Well, i headed back out to napa and got a new one (they let me exchange for free) and then i hooked up this one, did things a little different, and then it happened again! So this time i am going to just bend the rod back because i dont think napa will give me yet another free exchange.

Does anyone on here have any advice on how to bleed these systems? I have got to be doing something wrong if it keeps bending these push rods like this! I figured there is no way im the only one to bend the master pushrod like this either and someone probably has advice. This is very frustrating... And again, to be very specific, the truck is a 1987 K30 454TBI with an SM465 with the hydraulic clutch setup. If i cannot get anything to work i may just rip off the mechanical setup off my '83 and put it on the '87. Only problem is i heard people like the hydraulic better for wheeling. (this is my first 4x4 as well, so im new to the whole off-road thing). The worst part about this is that my 6" lift came in the mail today and i just wanna drive my truck! haha

Thanks for any advice!
Jason
 
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#2 ·
This is not a self bleeding system by far. There is actually a mighty vac adapter that attaches to the top of the fluid reservoir to pull a vacuum and bleed the system. That is the best way.

But if you can't find the adapter then unbolt the slave cylinder and point the bleeder as high as you can, have someone pump the master cylinder then hold pressure, crack the bleeder loose, repeat until all air is out.


You also need to check your master cylinder stroke length compared to push rod length and make sure there is no way you can bottom out the master cylinder. Remember you will have flex in the pedal assy. so account for that.
 
#3 ·
you need to find the source of the bending first. with the slave totally unhooked see if you can pump the pedal by hand and get fluid to come out.
 
#5 ·
Thanks for the input! I have heard from others though that this is a self-bleeding system, and that to bleed it you'll just pump the clutch a ton of times. I was doing that and after like 100 or so pumps the pressure did build up. So what else could that pressure be if it wasnt bleeding? As for the clutch fork.. I dont know why that would have gone bad only since removing the slave cylinder. I took the slave cylinder off and tried to pump the pedal while the bleeder valve was as high as i could get it, but not much fluid came out - that is why i got the new master. I seemed as though the master was where the system was clogged. After i replaced it, i put fluid in the reservoir, and then used the bleeding tool on the slave that pulls a vacuum and fluid then came through. I cant believe i'm having this much trouble, because it really is not a complicated system. Well, ill give everything a try mentioned here and see if it works out!

Thanks again!
Jason
 
#7 ·
Well it looks like the hose between the master and slave had collapsed internally. I took the hose off, tried blowing 120psi compressed air through it, and all that came out the other end was some very low pressure air. You could barely feel the air coming out the other end. So, i had to drop $70 on a new one! It's one expensive piece of line but all is well now. But, now that its all said and done and i have an entirely new clutch system, its nice. Everything works awesome.

Thanks for all your help!
 
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