79 ZX burning brake fluid?

[hitch]

I sold my ZX about 18 months ago. The new owner called today to ask if I knew why he was loosing brake fluid. Said there were no leaks and no residue showing on the wheels. Then told me that at idle, parked, if he pumps the brakes hard that it creates smoke from the exhaust. The only thing I could think of is the booster is bad and pushing fluid up the vaccuum tube? I don't recall how the booster is configured on the ZX, so I'd love help or suggestions.

[I'm BLUE]

Try the one way check valve , also master cylinders can leak from the rear and not show much if any signs of leaking ( think going into the booster ---> then sucked through the engine :blink: ) IDK , just a theory :D.

 

New owner absolutely sure nothing is leaking ? all lines checked 2-3 times.

 

My guess is Master Cylinder Leaking into Booster , then sucked through Booster with a possible bad check-valve from the intake to the booster.

 

Good Luck either way , this is something I would have to see in real life

[hang_510]

My guess is Master Cylinder Leaking into Booster , then sucked through Booster with a possible bad check-valve from the intake to the booster.

X2

 

remove the vac line and see if the smoke stops, solved if so!

[Pumpkn210]

Sounds like it needs the magic combo, master and booster! Usually the master goes bad and is either changed or ignored. Then cause of the brake fluid in the booster eats away the bellows in the booster. Then the engine sucks it in. However, it is usually caught before it gets to that point. Because by that time the vacume loss makes the brakes not work and the engine acts up, for there is a Huge vacume leak!

[datzenmike]

Try the one way check valve , also master cylinders can leak from the rear and not show much if any signs of leaking ( think going into the booster ---> then sucked through the engine :blink: ) IDK , just a theory :D.

 

New owner absolutely sure nothing is leaking ? all lines checked 2-3 times.

 

My guess is Master Cylinder Leaking into Booster , then sucked through Booster with a possible bad check-valve from the intake to the booster.

 

Good Luck either way , this is something I would have to see in real life

 

Why would the check valve be bad? It allows air from the booster to be sucked into the intake. One way, booster to intake.

[I'm BLUE]

Why would the check valve be bad? It allows air from the booster to be sucked into the intake. One way, booster to intake.

 

:rolleyes: ^^^ You just answered it , if it was 2 way then it would be bad wouldn't it ? :P :lol:. I have seen these go bad alone on other cars , and wreak havoc since they are an entirely different system/maker.

 

Some systems ( newer cars ) freak out with a little variance in the vacuum , even if leaking just a bit or not opening all of the way.

 

Check Valves go bad more frequently than credited for.

[datzenmike]

Brake fluid is (apparently) finding a way from the booster through the hose to the intake. Since the one way valve allows air in the booster to travel TO the intake and NOT the other way, how is a failed one way valve affecting anything? :blink:

[thisismatt]

Brake fluid is (apparently) finding a way from the booster through the hose to the intake. Since the one way valve allows air in the booster to travel TO the intake and NOT the other way, how is a failed one way valve affecting anything? :blink:

Shhhhh, Mike. Just slowly back away, don't make any brash movements...just back away...

[Pumpkn210]

Shhhhh, Mike. Just slowly back away, don't make any brash movements...just back away...

If you can, throw a bottle or something shiny to the other side of the room :lol: :lol:

[hitch]

Thanks everyone, and Hang 510 for the easy diagnostic method. Ratsun is a great forum. Mike, you are correct, after I thought about it, the check valve is allowing air or fluid to travel the correct direction.

[I'm BLUE]

Brake fluid is (apparently) finding a way from the booster through the hose to the intake. Since the one way valve allows air in the booster to travel TO the intake and NOT the other way, how is a failed one way valve affecting anything? :blink:

 

---- "how is a failed one way valve affecting anything" ----

 

try to hollow a brake booster check valve ( one way ) out with a drill bit or just simply hoke a hose straight hose from intake-to-booster , and get back to me if it doesn't affect anything you shouldn't feel a difference right ? :huh: ^^^ I also said it is a "possible" failed for helping diagnosing the one way valve, you know ---> as another item to check while he is tinkering on his rig to figure out the brake issue.

 

you must have you not experienced the fun side of "failed" check valves when trying to chase something down. To calmly put it check valves do fail , don't let anyone else tell you otherwise :D. Although some of them will just get full of crap or fall apart/stick open that I have seen. Not all from brake booster systems.

[datzenmike]

Not saying they don't fail only it doesn't really affect this problem I think. The one way valve is there to help store a reserve of vacuum in the booster. Without it, the booster would only have the same as what's in the manifold at the time. Worst case: You are accelerating hard (maybe on an on ramp, whatever) and suddenly a deer jumps in front of you. You instantly hit the brakes but manifold vacuum is very low from full throttle and your booster does not help you.

 

With the one way valve working properly you would have had vacuum stored and ready for use.

 

I found my 620 brakes rather weak after sitting all winter after an engine swap. Yes the booster hose was off and a lot of other things from the swap. Spiders or something had crawled up and into the one way valve and jammed it closed so no power brakes. I just threw another one in and they worked just like they should. Not quite the same thing but I have experience with them malfunctioning.

[I'm BLUE]

Not saying they don't fail only it doesn't really affect this problem I think. The one way valve is there to help store a reserve of vacuum in the booster. Without it, the booster would only have the same as what's in the manifold at the time. Worst case: You are accelerating hard (maybe on an on ramp, whatever) and suddenly a deer jumps in front of you. You instantly hit the brakes but manifold vacuum is very low from full throttle and your booster does not help you.

 

With the one way valve working properly you would have had vacuum stored and ready for use.

 

I found my 620 brakes rather weak after sitting all winter after an engine swap. Yes the booster hose was off and a lot of other things from the swap. Spiders or something had crawled up and into the one way valve and jammed it closed so no power brakes. I just threw another one in and they worked just like they should. Not quite the same thing but I have experience with them malfunctioning.

 

^^^ Agreed 100% man :P ;)

 

Interesting insight with the bugs/spiders crawling up there , mice tend to find the shelter in my area when it gets cold ( the cars of course :rolleyes: ) and tend to chew on wiring :angry: :lol:

[datzenmike]

I know the brakes worked well the summer I pulled the motor. I slipped a Z24 in and partially hooked it up and finished it the next spring. Damn the pedal was rock hard and at 3,400 lbs the truck felt like it was going to roll through stop signs. Had to use two feet. Checked for vacuum at the booster and there was none. A hose is a hose so that only left the valve and it had been left open on the manifold side all winter waiting for the engine hose to be mounted to it.