Clutch Woes

You replaced a worn out clutch master cylinder with a broken clutch master cylinder. And, maybe you failed to bench bleed the new one.

Jeff,

I'm suspecting the new one is bad now. I did draw all the air out of the new clutch master cylinder with a hand vacuum pump till I had no air in the clear tube *Before* attaching the main line. I just tried hooking up to the outlet and cycling it back through the reservoir as I usually would do on a Brake MC. I figured the single cylinder clutch MC wouldn't need the closed loop of a bench bleed if I was was pulling enough fluid through it with the vacuum pump and getting no air. Anyway I moved it slowly in and out until there was no more air. It maintained no air until I then moved it quicker and I immediately got more air introduced. Move it faster and larger air bubbles enter the line and are pushed into the reservoir. I'm thinking I'm back to the parts department for another. Or perhaps I can press the clutch in very slowly from here on out! ;-)

Thanks for your help!

Perry

Jeff Strickland wrote:

Perry,

I posted you in the other NG. This sounds like a bad MC to me, like someone forgot to install a seal or put one on backwards. Bleeding this system should be fairly easy, I did one for a friend a while ago from below with a hand vacuum pump and it works like a charm. I'd try one more vacuum bleed or even try a pressure bleeded if you can get one. (Motive Products makes one that might work for you.)

I don't think you can do it that way. What you have to overcome is the fact that air bubbles get inside the respective chambers, and the pedal does not move far enought to force them out. When you work the piston while the MC is on the bench, you can push it further than the pedal will move it, and this will push the trapped air out.

See above. I think you MUST bleed the air by pushing the piston its full travel, and the pedal will not do this.

I think you have a serious problem. Get a new MC, and bleed it on the bench before you install it. In any case, if air is entering the system somewhere after you get the bubbles to stop, you have a leak.

Final follow-up for this NG, Though most of you monitor both it seems.

I started this thread after I ran into a confusing problem for a basically simple clutch system. I spent way too much time and money trying to get a firm clutch pedal once again.

I chose not to buy a rebuild for the clutch master cylinder even though it was less than half the price. I figured if I bought another one it would be locally and I would be able to exchange it easier since I wasn't 125 miles from the last place I bought the first replacement. (also, by this time, I was pretty much doubting my ability to do anything right by this clutch so I decided to KISS it)

My First MC I bought was made in China so I guess I got what I paid for. My last one bought was cheaper ($84) a Wagner and it looked cheaper than the china one but at least it came with an instruction pamphlet. This said clearly, "DO NOT Bench Bleed" across the sheet. It went on to say that bench bleeding may over stroke the piston and damage the valves for this type of master cylinder. So I just installed it and low in behold it started to build pressure immediately during normal bleeding. Then I did a silly thing and pulled up with my hand on the clutch pedal. Ping! The shaft pulled right out of the MC! Upon closer inspection a very cheesy bent wire internal clip was used instead of a proper internal hardened retaining ring. It popped out without any effort. So out comes the MC again and I take a good retaining ring from the collection of bad MC's I now have and all is finally well. It was in, bled, and I was wheeling again in less than 10 minutes! Woo Hoo! I was forgetting what it was like to crawl up and play in that bad mama!

I still wanted to know what happened to the new MC made in china that failed almost immediately. So I took it apart after a long ride today and unlike my original and my new wagner MC it had only one seal in it. Not one missing out of two but only one seal, period. Made in China holds true to quality again.

I appreciate all the help from the fine folks on this NG. Hopefully this follow-up will help folks to looking closer at their replacement parts and who makes them. Though price did not mean quality here. (unless I went to mopar of course) I certainly will weigh that next time.

Cheers!

Perry

Jeff Strickland wrote:

Well, I am glad you read the directions instead of listening to us. ;-)

Perhaps the bench bleeding is needed in the multi-chamber master sylinders, and the clutch is a single chamber design. I would not have guessed that bench bleeding could be a problem.