Yeah, very frustrating. I just wrapped up a steering rack rebuild/motor mount replacement job, so was looking forward to getting it back on the road in the cooler weather. (I guess it's possible raising the engine stressed a joint in the clutch system, but since it's happened regularly before... ) Hoping to drive it to Marble Falls in one month, but not sure I trust it at this point. I'll check into the flex line options.

 

Well it wasn't the flex hose, but I have a new GB flex hose on coming anyway...

I went out to check the MC this evening and found that I had left the pedal all the way down. When I pulled it up, the piston in the MC didn't budge. I used some ring clip pliers, which work great for this by the way, and pulled the piston out. Big chunk missing from the seal. (picture is a end view so the missing chunk is visable)

This was a new MC in June. I can't say for sure which way the spring came out, but I'm thinking it was big end first, which would have been backwards. If so, this could have bound with the seal and the side of the cylinder wall and torn the seal. I don't think I ever opened this MC up since I wouldn't have had a reason too. Anyway, time for a 2nd MC to go with my 3rd slave cylinder. Of course I'll just replace the guts.

 

Ah, I just remembered, I did open it up because I followed Stan's instructions for trimming the tip of the piston down. I didn't shorten the spring though, so maybe we are seeing the results of partially following one of Stan's recommendations...

 

Don before you put anything back together,
please do some thread searching for cutting down the MC piston ,
this will also include reducing the spring length.

That seal appears to have fractured most likely due to different chemicals touching it.

At this point i would suggest that you replace the complete clutch MC,
and modify the spring and piston before you install the new part.

A fresh flex line would also be advised as you will have the system apart.

Make sure from now on you use only ATE super Blue OR ATE Gold,
no more flushing different fluids through then doing a final bleed.

From looking at this I would also make a guess that the brake MC may also be in line for replacement

NOTE don't spray brake cleaner on any of the rubber parts of the system as this can damage them

 

Don:
You mention that this is your 2nd master cylinder. I'm about to undertake the blue hose job which necessitates a master cylinder replacement as a while-you-are-in-there job. There was no mention of how you attacked the M/C removal. Did you remove the brake master cylinder and brake booster (which is what I'm about to attempt).

I've read through everything I could find on the web on the M/C removal and bleeding. Also consulted the WSM where it indicates removing 4 brake lines from the M/C. My '89 has 2 brake lines because of the ABS; am I correct?

Also loved the video someone posted from BMP Design where they use an oil can to bleed the system which makes huge sense.

Bob

 

Bob, I was able to wiggle mine out without messing with the brake lines or booster. It's a tight fit, but it went in pretty easy afterwards. Getting the MC bolt holes threaded is the fun part


Don, why not use the stock MC and not bother cutting the new one up? Or is this some kind of parts mod on an aftermarket unit?

 

the trick to get the MC into place is to get a long 13mm bolt cut the head off and then feed it through one of the bolt holes screw it into the MC and then use this stud to pull the MC into place.

Ducman the new clutch MCs are different ,
the piston has been changed it is longer and thus it will not provide the stroke that the old unit did.
This requires that about 4.5 mm is cut off the tip of the new piston as well as shortening the new spring about 2 winds, slot the tip of the piston

 

I was able to replace the MC without removing the brake MC or lines. As stated it's tight but doable. What worked for me was using wire to pull the MC into place from inside the car. It didn't seem as bad as everyone makes it sound.

Stan, I don't see how chemicals could remove a chunk of the seal but you've seen more of these than I have. I'm using only the outlaw blue fluid now. I've seen your threads on trimming the piston, and that's what I did, but didn't shorten the spring since I had had so many pistons get stuck in the bore, I wanted all the spring power I could get. I'm hoping the spring was in backwards, at least that's an explanation that sortof makes sense. If the large end of the spring is on the piston side, it doesn't stay centered, and can bind with the seal. I'll be waiting for the GB hose to reassemble, and will probably have to buy another MC to get the seals I need.

 

That's the trick I ended up using.

 

Looks like Roger is going to take care of me once again on the MC, thanks Roger! This car may make it to Marble Falls after all...

 

the big concern with the spring is that it will be too long,
thus when the pedal is pushed all the way,
the spring goes into coil bind,
this will cause the spring to fracture,
then it will send lots of small metal pieces into the clutch hydraulic system.
The metal will quickly cut the new seals and then you have to start over.
If the seals in the MC are good you shouldnt have any issues with it returning
I have seen this a few times,
it requires a complete flush of the lines,
then blow out with compressed air.

 

Does anyone sell a rebuild kit for the M/C? Mine works just fine when I shut the car down for the work I'm doing. All you would need, in a well-functioning M/C, are new seals thus side-stepping the piston and spring trimming.

I'm going to pull the booster because I can see rust forming on the bottom of the unit looking from below and might as well deal with it being that I've gone this far. Any tips/hints on removing it?

 

No rebuild kit available. I will only be replacing the guts this time. Since it's fairly easy to pull the piston and modify it and the spring later if needed, I'm not going to trim anything this time and see if there are any gear grinding issues.

Brake fluid is very corrosive, so that may be what you are seeing.

 

The parts arrived from Roger on Saturday and the car is back on the road (I'm getting really fast at clutch hydraulic work with so much practice)

I replaced the piston and spring of the MC with no modifications and it shifts fine, no grinding.

Also installed a GB flex hose since the stock hose seems to be a common source of problems.

While pumping the slave manually to bleed, I noticed there was again fluid in it's boot. I took it apart and there were no problems with the seals so not sure why this keeps happening. Maybe when the pedal slams to the floor with it's spring pressure, some amount is fluid is forced past the seals in the SC?

Hopefully I'm done with clutch work for a while.

 

Don if there is fluid in the boot the seal is leaking.
I would suggest to replace the slave then you should be good to go,
if the MC had a bad seal probably from some fluid issues, the slave is sure to follow,

since your finding fluid its leaking, so your almost finished with the clutch