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Discussion Starter · #1 ·
My 85 900 brake peddle was going to the floor with very poor braking power. No leaks are evident, no fluid loss (have pumped them many many times), so I figure, ok new master cylinder. Installed the bench bleed MC and still have exact same problem. Tried to bleed one of the calipers but very little fluid comes out. I first used a vacuum bleeder, then went to the tried and true peddle method with the same results. This is a pretty simple circuit, and I just can't figure out whats going on. Pumping the peddle does not yield a stiffer peddle. Is there anything else in the circuit that could cause this? Do I have a faulty new MC?

Please help!
 

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Bleed all of the calipers, preferably with a pressure bleeder. Fill with new fluid, then see how it is.
 

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When my MC went a couple of years ago it took a tonne of bleeding to finally get the brakes up.

Also the system is split-diagonal so bleed
LF
RR
RF
LR

And repeat.
 

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Discussion Starter · #4 ·
But why the bleed problem?

Any idea why very little fluid comes out of bleeder? I only tried one caliper, but I would say about 1/5 of what I would expect to come out comes out.

I do have one bleeder that is completely rusted shut, so that will be a project in itself.

Actually this is no longer my car. I sold it to a friend in "need" (had no money) on the easy payment plan, and I'm trying to help him keep it patched together till he pays me...every penny he spends on the car is money I don't get.

One thought is that the caliper I was trying to bleed is the one that has the sticking e-brake. Could the brake have stuck on him and boiled/melted something internally???

Iv'e bleed many a brake, and something is just not right with this one. I can't help but think that it is related to the "pedel to the floor" problem.
 

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This is a very messy, not recommended methodology but - it might work. Bleed the calipers you can using the nipples, on the others, instead of using the bleeder nipple, loosen the hard line where it attaches to the caliper - that MIGHT get the air out of the system enough to give a decent brake pedal.
 

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Are your bleed valves nice and clean and without any goo blocking them inside?

I also learned that if the pedal (and master cylinder) does not retract completely so it even have a bit of freeplay before touching the master cylinder, the little passages inside the cylinder may not match up and fluid from reservoir will not get to the plunger.
 

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Discussion Starter · #7 ·
Thanks for the replies. I'll try the hose off approach. It just seemed funny that the problem with the new master is the same as the old one... Thought maybee I had a different problem.

Maybee I should blow compressed air through the caliper while the line is off to clear it out. There did seem to be some crud coming from the caliper. (Had the bleed nipple out to clean a couple times.)
 
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