Brake Woes

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2002turbo

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Ongoing saga .... have replaced all rubber brake lines, cleaned out the proportioning valve, replaced front calipers, replaced brake pads. This started with the brakes binding. That stopped when we put a couple washers between the booster and the MC so we deduced MC shims were the culprit, but in dealing with that we found it seemed to be leaking from the rear. Replaced MC with a NOS one OEM marked 22. I think that's a small bore MC. That one would not give a consistent hard pedal even with the lines blocked off. Fluid was bypassing. Rebuilt the old MC marked 23, with a WN kit. Now the brakes are not pulling but the reservoir drained completely overnight, twice. Again, fluid seems to be coming out the back of the MC. So the obvious diagnosis is leaking seals; but three MCs in a row leaking? Can the shims possibly be the common denominator? Or something else?
 
Do you have the proper o-ring to the booster, and did you adjust the rod to MC clearance properly? I have a thread on this. I don't understand the shims either.
 
Yes, the o ring is there, it came with the WN kit. I thought the rod to MC clearance was adjusted via shims? If this is not correct, would it allow leakage out the back? I don't see how it could.

Could not find Stevehose's thread. Link?

Thanks,
 
2002turbo said:
Yes, the o ring is there, it came with the WN kit. I thought the rod to MC clearance was adjusted via shims? If this is not correct, would it allow leakage out the back?
Click to expand...
MC's typically leak from the rear when the rear seal inside the MC is worn and the vacuum of the booster draws fluid past that compromised seal. If anything, if your shims are not airtight (e.g., if they are just a couple of flatwashers), the lack of a vacuum inside the booster would lessen fluid leakage.

2002turbo said:
Again, fluid seems to be coming out the back of the MC. So the obvious diagnosis is leaking seals; but three MCs in a row leaking?
Click to expand...

I agree that it seems odd that multiple MC's would all lose fluid the same way. But I don't have an explanation other than bad luck.
 
As I understand it, the large O ring at the booster is for vacuum not fluid. The fluid is supposed to be fully contained by the seals. If the fluid from the reservoir is leaking out overnight, it must be bypassing the internal MC seals. We will pull it apart and check the seals.
 
2002turbo said:
Yes, the o ring is there, it came with the WN kit. I thought the rod to MC clearance was adjusted via shims? If this is not correct, would it allow leakage out the back? I don't see how it could.

Could not find Stevehose's thread. Link?

Thanks,
Click to expand...
By shims do you mean the washers?

Stevehose

Post in thread 'Brake problems - Hot Wheels edition'

Ok I wish I had read the section in the manual about how to refit the master cylinder and the clearance needed, figured it was just a bolt back on deal. I read the brake booster section but no mention of that of course. So feelin’ kinda dumb here lol.

Here is the removed tip, obviously sent to me with my choice of 3 different thickness washers to match up with the MC.

So do I do the plastigauge like the manual says or is there a shade tree way to do this? Not sure how plastigauge is going to stay in place in the MC during assembly. But I have some.

The head of the tip is 8mm, the...
  • Wow
 
You shimmed the tip of the shaft correct?

There are different lengths of the tips.

question - did you just recently change your brake booster?
 

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Local mechanic (smarter than me and a whole lot more expert) did the work. However he did screw the pooch by leaving the washers I put on the booster studs (temporarily) to diagnose the original brake binding problem. That did make the problem go away. The leaking developed later, after we changed just about everything but the booster and the MC twice. And by shims I mean washers yes. The shimming should have nothing to do with the fluid leaking if I understand how this works. That just allows for the right amount of play before the booster kicks in.
 
// and fwiw the WN kit does NOT include a dust seal, and the included grommets are the large hole variant not the small ones that we needed. We had a good set of new small hole grommets from a prior attempt though. I have extra WN kits for anyone who wants one, believe me you do NOT want to deal with UPS/customs what a cxxxrfxxk that is.
 
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