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Re: [T3] Brakes have me confused!


On 13 Oct 2003 at 9:49, Erik Litchy wrote:

> ok when i got my car i tried the brakes and they were frozen from lack of
> use, actually all the pedals were.  i sprayed penetrating oil on them and
> gave them a good kick that freed them.  but upon filling the brake resivor
> the fluid leaked from the piston area (even without pressing the pedal).  so
> i got a reman master and installed it.  same problem, the fluid leaks from
> the piston area for some reason.  so i returned it and got another from napa.
>  this one was another casting, i thought good.  so I install it diffrent,
> leaving off the switches and pour the fluid in unitl no more air comes out,
> then screw in the switches.  i had taken out the pushrod off the pedal
> assembly to make sure it wouldnt be a factor.  the fluid was leaking before i
> got to push the rod in.  can the seals be in backward?  is it my error? 
> wrong brake fluid?  does it take the british fluid?  Girling? 

It is most likely that the parts you're getting have sat too long on the shelf 
and have rusted in the bore. The rust pushes the seal lip inward, leaving room 
for fluid to leak out. Especially on the last one, where you left the pushrod 
out, I don't think there's anything you could be doing wrong. No special fluid 
is required.  

You really want to clean up the spilled fluid quickly, or it will peel up the 
paint, leading to rapid rust. It is completely water soluble, so it cleans up 
easily with water and a sponge, or rag..  

> so should i get a 4th master cyl, at this rate it makes me feel like its
> something im doing, but i have installed masters in other cars and trucks
> without inncident. 

If you do this again you might want to just open the mouth of the new MC and 
take the first piston out so you can inspect it there. Reject it right away if 
it is rusty in the bore. Rusting in storage is a big problem with brake parts.

If you still have your original ATe MC I can rebuild it, probably for less than 
what you've been paying for new ones. What does NAPA charge for one of these? I 
charge $45 to rebuild one, but, in general, I only have parts to rebuild the 
ATe ones.

> another question how does the rear brake system work?  i know that there is
> supposed to be in drum systems some residual pressure around 15 psi?  how is
> this accomplished? 

Older cars certainly did use the residual pressure valves, but none of the 
tandem cylinder type 3s ever have. No residual pressure valves are used in 
these systems, and none are needed.   

I've never understood why it might be desirable, but someone on one of the 
newsgroups claimed that some cars have the reservoir lower than the slave 
cylinders. In such a case you could get negative pressure in the slave 
cylinder, which might tend to draw in air around the seal lip. I have a hard 
time imagining any vehicle built like this, but if someone knows of one, or of 
any other reason why a residual pressure valve might be needed, I'd love to 
learn about it.   

-- 
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054
USA

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