You have vacuum assisted brakes. The only thing that can leak fluid is the master cylinder. The other possibility would be water that somehow got between the 2 parts but that is not a normal problem.

Either you spilled some brake fluid or you got a bad master cylinder. If you did not spill any brake fluid take the master cylinder back.

 

Alright thanks man, I asked my buddy who's a mechanic and he said the same thing. I guess I got a faulty master cylinder. Ill be buying a new one tomorrow

 

If any brake fluid makes it's way into the booster it will rupture the diaphragm inside due to the fluid's corrosive nature... It's always a good practice just to replace both at the same time, especially if your old MC was leaking out of the back of the piston. Brake boosters usually cost 2-3 times what a reman'ed MC cost, which is why they typically don't get replaced... Plus, the mounting bolts can be hard to get too if you're not well seasoned.

You can alway go drive the trucks around for a bit and then rebleed the brakes. Sometimes air bubbles get stuck in hard to reach places.

 

Always try to buy a new master cylinder, remanufactured are junk and will almost always leak out the cap.

I also went through 3) A-1 Cardone junk brake boosters in a row from Napa to get a working one.

Jim

 

Yeah the master cylinder was new.. Don't know why it would be leaking. I ordered a new booster too

 

Bringing my thread back.. I got a new booster and a new MC and it was leaking from the MC. I had Advance Auto Parts order me a new one and it is leaking again. I just had them order me a third one. Any ideas why it is still leaking? Anyone else have this problem? It looks like it is coming from the cap seal.. but not certain.

 

Is it leaking from under the cap?
Every re-manufactured master cylinder that I have tried leaked profusely from under the cap because the sealing surface was all dinged up.

The last one I bought was new and I still had only a very slight leak, just enough to get one side wet so I removed the rubber gasket and cut a shim out of a Manila folder and placed it behind the rubber gasket, this applied just enough pressure to seal the cap, I also lowered the fluid level to about 3/8"
thinking my rough ride must also be splashing the fluid over the top.

It worked for me.

Jim

 

could maybe hit the top rim of the master cylinder with a sanding wheel? make a better mating surface. this is something i've been wanting to try, that top is just a rough cast edge

 

i bought my truck about 2 months ago, my first ctd, and it was leaking out of the cap. i had never seen this before so i was doing a little research as to why. someone on this forum said they've been driving these 1st gen trucks since they were new and every single one of them leaked out of the cap eventually, especially these trash reman MC's that they sell at the local parts store. i've been meaning to ask the forum, does anyone know of a plastic reservoir MC that will work on these trucks? I guess a little research could solve this (piston diameter/bolt pattern)

 

Thanks for all the replies guys. I think it is the top of the master cylinder where my leak is coming from. I would think a new one wouldn't leak..

 

well doing some research, apparently the MC from a 90-97 dodge van will fit the 1st gen booster. it has the same size bore, connectors, and a plastic reservoir with screw on caps. i will be getting one very soon and will follow up on how the install went.

i think this is the part i'm going to try first

NAPA AUTO PARTS

 

It looks like it would fit.. I might buy that as well. It shouldn't leak with the screw caps!

 

I bought the van master cylinder today... It does not fit

 

damn, that's disheartening, i went to a few parts houses yesterday trying to find one that had both M/C's in stock to compare side by side, no luck. i guess the search continues then. is the bolt pattern to the booster just different?

 

The bolts line up but are smaller on the MC so it would need to be drilled out. The rod also is too big for the van MC

 

is the rod too long or wide? it is the same size bore (1 1/8") which would make it odd for it to be too wide. i've been researching more today, that is the only one i've found in any tech articles to be "compatible".

 

Rod is too long