Pierburg Pump, Brakes, etc., etc.

[E. Roy Wendell IV]

> On my car, it's the full-court, four-wheel press.  I've changed the  
> rear
> rotors, calipers, pads, lines, fluid, etc., and the fronts are  
> still in very
> good shape, so I'm left fishing at this point, and my first suspect  
> is the
> M/C.  Nothing's getting cheaper -- try finding a rebuilt for $40  
> anymore,
> but if replacing it solves the problem I'll be happy.
>
> What I'd *really* like to do once I put the new one in is cut the  
> old one
> open and have a look inside.
>
> Alex

No need to cut it open. Just drill a couple of small holes in the  
circlip so that you can extract it using standard snap ring pliers  
and then whack the master cylinder against the workbench a couple of  
times so that inertia pops the phenolic end cap out. Then be treated  
to the innards of the most complicated brake master cylinder I've yet  
encountered.

On my first go around with this problem on my 86 5ktq I installed the  
new master cylinder and took the old one apart expecting to find  
massive amounts of corrosion on the cylinder bore. I was completely  
puzzled when it appeared to be in good shape. At the time I just  
shrugged my shoulders and tossed it. After spending more than a month  
driving around with an 11mm wrench in the center console so that I  
could release the brakes every time I used them I was just happy to  
have the problem fixed no matter what the method.

When the same problem occurred on the 200tq I bought last November I  
decided to do some more research on the problem before ordering a new  
master cylinder. I was motivated by the fact that the 200tq master  
cylinder cost more than double what the 5k piece costs. I  
investigated backdating the brake system to the 5k parts and it's  
doable as long as the master cylinder and front calipers are  
compatible. In any case, I found a post from a fellow lister saying  
that the sticky brakes problem is due to a failure in the check  
valves built into the master cylinder pistons. While he recommended  
just replacing the master cylinder, economics and sheer reluctance to  
throw away anything that might be fixed motivated me to disassemble  
the master cylinder. When I did so I found the check valves in  
question. Unlike the master cylinder body and pistons they are steel  
and had a little rust spot on them where they met the port on the  
piston. I used a piece of scotch brite to get the rust spots off the  
check valve and used a shop rag with soap and water to clean  
everything else. I lubed everything up with brake fluid and put it  
all back together with the check valves rotated to a new position.  
It's been fine since November. YMMV of course.

E. Roy Wendell IV
erwendell at mac.com
Too many type 44 tq
A pair of MR2s