Brake Problem?

[stefan]

So i'm minding a few weird brake things that I've never noticed before. One is that in the morning the pedal is hard (as though you pressed it several times with the engine off). Two, is that I seem to be able to overwhelm the system a little too easy, even when the car is running. Like 2-3 presses of the brake pedal with engine running and it is hard again, then slowly it goes down to the floor as it catches up.

I'm not sure what symptoms of a brake booster issue vs a master cylinder issue (and then I believe there is a servo in there somewhere too??) To me this seems like a vacuum issue with the brake booster. I checked the main lines to it for cracks, and all looks good. Solid vacuum up to the booster, and the check valve at the booster seems good. So if this is an issue, it seems to be within the unit.

Does this sound familiar to anyone? Does it make sense that this could be the booster?

[BaggedGLI]

Re: Brake Problem?

If it was master, holding pressure on the pedal you would see the pedal slowly go down as fluid leaked past the piston.

Sounds like a vacuum issue with the booster, faulty check valve, faulty pump? Those pumps are notorious for the fitting leaking. Possibly the booster but few and far between on booster failures.

[stefan]

Re: Brake Problem?

If it was master, holding pressure on the pedal you would see the pedal slowly go down as fluid leaked past the piston.

Would this be the case even when the car is off? If it is off it stays high. If running, it gets hard after a couple presses and stays high, but then slowly moves to the floor (booster catches up and assists, in my mind... but admittedly don't know 100% how the parts interact here).

The tandem pump is pulling a lot of vacuum. I'm fairly certain it is ok. The check valve right at the booster let out a big hiss when I popped it out of the booster (with car off) so it was at least working at that moment. I was pretty sure I hit all these lines with a mityvac when I was trying to work out my idle issue and found everything holding, but maybe I have to re-visit the stuff right at the pump. Should everything hold vacuum after the car is off? If I pull a vacuum with mityvac on the line coming off the tandem pump with the car off, should that be sealed?

Thanks for response!

**Update: Took apart the large vac line at the fitting at the firewall. Line from there to booster seems to be holding (hard to load that side up with a lot of vacuum - must be a large volume of air to suck out from the booster... but once I got some vac, it held). Then tested from the same fitting the other way (so capturing everything coming off the pump), and that also held vac.