1981 brake booster

[fstf2v]

My 81 toyo brake pedal goes to the floor. Push on pedal and it slowly goes to the floor. seems only back are working. How do I check the vacumm booster. When the brake started doing these it seemed to need brake fluid ,but didn't. Master cylinder is full and is about 8 months old.No leaks are visable. thanks- fstf2v

[Harvester]

The condition you describe is typical of leakage inside the master cylinder. I think you need to replace it. Leakage inside the master cylinder won't show up as external leakage or fluid loss. It allows fluid to leak past the internal seals and return to the resevoir instead of holding pressure in the lines.

Harvester

[fstf2v]

Thanks Harvester, I'll open her up and see if this solves the problem. fstf2v

[fstf2v]

OK ,here is what happened. My old master cylinder is the original one and the one I got 8 months ago is aftermarket, (china) I suspect. My old one has better quality pistons and springs. So I replaced the old into the new cilinder body(case). Then bled the truck brakes , now they are hard and firm. Thanks, Harvester for your info.... I didn't know a master cylinder could leak without leaking. [smilie=pdt_aaa.gif]

[Harvester]

Glad to hear you have the situation corrected.

Thanks for letting us know the outcome.

Harvester