GVR-4 Brake fluid disappearing!?

[Spookcorleone]

Well its not really disappearing, I know its ending up on the ground in my driveway.

Every 3 days or so I have a "REFILL" my brake res. Its leaking badly some place in the front (it appears to be coming from that big black housing with the name leaves me right now... brake booster? I forget.) it managed to run down the oil-pan and onto the ground from there - which at first tricked me into thinking it was a oil leak... har har har ... love DSMs.

Either way wondering if there is a part of my system that for the most part dies off at around 130K miles, just started recently.

Thanks guys.

 

[ChicksDigBoost]

Sounds like one of the seals in the master cylinder is leaking.

 

[boostedinaz]

Sounds like one of the seals in the master cylinder is leaking.

I agree.

 

[Spookcorleone]

like I said before I didn't get a chance to jack up the car or even really get a detailed look under the hood (to damn hot out and I had to drill/tap/helicoil an exhaust stud so I had my share of fun for now!)

Either way I felt under the master cylinder and I don't feel any fluid on it - it appears that the black thing that the master bolts to might be the problem... that is the brake-booster correct?

Either way I'll check it most likely this weekend and I'll have a reply posted if thats not the problem! Thanks for the help as always.

 

[boostedinaz]

like I said before I didn't get a chance to jack up the car or even really get a detailed look under the hood (to damn hot out and I had to drill/tap/helicoil an exhaust stud so I had my share of fun for now!)

Either way I felt under the master cylinder and I don't feel any fluid on it - it appears that the black thing that the master bolts to might be the problem... that is the brake-booster correct?

Either way I'll check it most likely this weekend and I'll have a reply posted if thats not the problem! Thanks for the help as always.

The brake booster doesn't hold fluid so that is not the problem. The problem is most likely a bad seal in the master cylinder that is causing the leak to drain into the brake booster.

 

[Iluvskanks]

when you go to the parts store ask for brake fluid stop leak see what they say. Then if they are smart enough and say there is no such thing then say does that mean the rest are gimmicks.

 

[boostedinaz]

when you go to the parts store ask for brake fluid stop leak see what they say. Then if they are smart enough and say there is no such thing then say does that mean the rest are gimmicks.

Oh my god.

So the only thing that will stop your car and you decide to use some BS stuff to half ass fix it. I would hate to be the person in front of you when that shit doesnt work.

Why not just save a few bucks and actually fix the problem?

 

[Defiant]

Don't feed the trolls.

 

[Spookcorleone]

Ok well I took Iluvskanks's advice and now I'm not leaking any more! I hope that stuff holds out!

!!!!
I'm joking.

Its leaking right where the master cylinder bolts to the brake-booster.

I didn't take it off yet but thats the place. There is a gasket between that I am guessing correct?

The car wasn't driven hard for awhile (until I recently got it on the road) so now alot of problems are poping up - guess once I got it under a good bita pressure the gasket gave me the finger and quit on me...

Also whats a good site to buy a DSM engine from? (92 or 93 the best head-wise? I plan to port/polish and build up so I can swap into my car - will be my first DSM swap so I wanna see how it goes.)

Either way... yeah.

 

[Spookcorleone]

Ok I have the master cylinder off - but now I don't know what I'm doing!? I am pretty sure it was leaking where it bolts to the brake booster, but I've no idea how to inspect this thing. I know I've got to remove the ring to disassemble it - but how do I tell if it is 100% the master cylinder?

Thanks!

 

[boostedinaz]

Ok I have the master cylinder off - but now I don't know what I'm doing!? I am pretty sure it was leaking where it bolts to the brake booster, but I've no idea how to inspect this thing. I know I've got to remove the ring to disassemble it - but how do I tell if it is 100% the master cylinder?

Thanks!

I promise you it is the master cylinder. Just buy a new one and put it on.

 

[MGushard]

So this thread answered my question, had the exact same problem and wasn't even driving the car. Fluid just went away after a few days, thanks! Now I have a question, can the master cylinder seal be replaced or do I need a new unit? I'm sure it could use a new one but just to get it on the road..

 

[Dericsh]

So this thread answered my question, had the exact same problem and wasn't even driving the car. Fluid just went away after a few days, thanks! Now I have a question, can the master cylinder seal be replaced or do I need a new unit? I'm sure it could use a new one but just to get it on the road..

I haven’t seen any rebuild kits. I did a quick search to make sure and didn’t come up with anything. I found a clutch master cylinder rebuild kit but not brakes. Looks like you’ll be sourcing a new one.

 

[MGushard]

I haven’t seen any rebuild kits. I did a quick search to make sure and didn’t come up with anything. I found a clutch master cylinder rebuild kit but not brakes. Looks like you’ll be sourcing a new one.

Thank you! After more troubleshooting and research I discovered the brake booster is bad. This explains the fluid leak and the idle dropping when pushing on the brake peddle, and it running very poorly when on a test drive.

 

[1990TSIAWDTALON]

Make sure you have a check valve inline with the booster.

1992 EAGLE TALON 2.0L L4 Turbocharged Master Cylinder Repair Kit | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

www.rockauto.com

Boosters don't leak fluid though, master cylinders do. Just to clarify.

 

[MGushard]

So another brake booster related question.. and I think I know the answer but just want to verify before I spend any more bucks. Before I put the new booster on and all back together, I want to make sure the master cylinder is good. I have it off the car and it has no fluid in it, but don't have plugs for the outlet ports to bench test it as recommended. I can plug up both outlets and one inlet with my fingers and blow into the other inlet, air still gets out. No matter which combo I use of plugging up ports and blowing into the 4th one, air still gets out. Does this mean it's bad or do I need to have fluid in it to test properly. When I took it off there were no obvious signs and fluid leaking, it was dry except for a bit inside where it connects to the booster by the plunger. I don't mind getting new parts as it has been sitting for quite a few years and I want to cover everything that could be a serious problem. I'm almost ready for new tires to get on the road, ya'll been very helpful, thanks!

 

[CKOPOCT]

Conceptually the brake booster is nothing more than a soda can with a rubber diaphragm in the middle of it - no fluid of any kind. The vacuum hose is plugged in on one side of the booster, and the vacuum pulls on the diaphragm. It is a booster because of the amount of force it takes for you to apply the brakes - you are trying to use one foot while driving to apply over 100psi to your brake system. The vacuum booster helps to "pull" the brake pedal down when you step on it. When brake boosters go bad it is the diaphragm that gets a hole or tear and the booster no longer holds a vacuum. As a result your brake pedal gets stiffer - it becomes harder to push on the brakes. (There are other ways a booster fails, but don't need to go into that right now.)

The brake master cylinder uses what is called an umbrella seal. Imagine if you put an umbrella in a pipe and opened it up so the edges of the umbrella touched the entire diameter of the pipe. If you were to pull on the umbrella the edges would scrape against the pipe and the umbrella would be hard to pull. In contrast if you pushed the umbrella forward it would slide easily because it is designed to collapse that way. In a similar fashion the umbrella (or cup) seal of a master cylinder widens outward when you press on the brakes, forcing the fluid through the lines. When you let off the brakes the seal relaxes and the pedal easily returns back to the top. Master cylinders generally "fail" because there is a problem with the umbrella seal - a tear or crack that lets brake fluid get past the seal. The result is a leak that comes out where the piston/plunger is (where the master cylinder bolts to the firewall).

If you have disappearing brake fluid and a brake leak at the master cylinder you may have weak brakes (depending on how bad the leak is) and you'll probably see an area at the bottom of the brake booster where the paint is blistering or coming away. This is because brake fluid absorbs water, and it also soaks into paint - so the water in the brake fluid reacts with the metal and breaks down the bond between the paint and the metal (forms rust). Easiest way to tell a brake leak - paint problem.

Anywho - all of that to say that if you had a fluid leak it is not your brake booster. Inspect the old booster and the areas directly below it to see evidence of brake fluid. Given what you have shared I would guess you have a bad master cylinder and should replace it.