Vacuum Brake Booster....can you test if it is shot?

[Buicksx2]

Hi All,

I got vacuum brakes in one of my cars and have never liked the way the pedal feels, too soft and to the floor.

I am wondering if there is anyway to test the booster itself and if so how do you do it?

Or should I just go and buy a new booster and re-bleed? Dont want to take car to track until I am confident car will stop.....kinda important......lol.

Thanks in advance for any and all help.

[Just a Six??]

My vacuum brakes are great with no pedal to the floor! If you had this problem from day 1 either bleed them again or just get another booster as they are not real expensive. Of course this is based on that the rest of the system is fine & working properly?

[Buicksx2]

Thansk for the reply, any idea how much the boosters go for? I will stop at NAPA on way into work tomorrow. Wanna get car to track but wanna make sure she stops.....lol.

Thanks again.

[Steve Wood]

You got an ac vacuum pump or something else that you can attempt to pull a vacuum on the booster and see if it will hold one? If the diaphram is bad, it won't hold vacuum...

Or, run the engine so the engine is pulling a vacuum and then cut it off and pull the check valve out of the booster after a couple of minutes and see if you hear the air rushing in.

[Rickracer 1]

Usually they will hiss like a vacuum leak underneath the dash when the brake is applied, or will just have a hard pedal. If you have a low pedal, it is most likely either a hydraulic or adjustment problem, or possibly a little of both. I would recommend a rear brake adjustment, parking brake adjustment, then bleeding the system thoroughly, starting RR, LR, RF, LF. It may be a bad master cylinder. To check for a bad master, try depressing the pedal very slowly, noting pedal height, (motor off, but with full idle vacuum stored), then crank it up for a few seconds to build vacuum again, shut if off, and depress it again quickly and sharply. If there is a difference in the pedal height, or if it drops gradually from the initial height, chances are it is bypassing internally and needs to be replaced.

[Buicksx2]

Hi Rick,

Thanks for the reply. Car has a Moser 9" and Wildwood brakes and we had to make our own brake lines and the Ebrake is not hooked up on this car. I have a Lokar kit to install to have it mate with the Moser rear.

I assume this original booster in car with well over 130k on it, so it probably wouldnt hurt to replace it and re-bleed everything all over again. Pedal is way way too soft and to floor.

Thanks guys for all the replies, keep em coming.

[Rickracer 1]

I added more detail. And you're welcome,

[Steve Wood]

What makes you think the master cylinder is good on both sides?

And, is it the right unit for your brakes?

[Rickracer 1]

?

[Steve Wood]

What is your question?

[Rickracer 1]

What makes you think the master cylinder is good on both sides?

This thread is almost an I/M, LOL.

[Buicksx2]

Thanks again guys, appreciate it. FWIW we used the original brake lines that go back over the rear and goes into that brass fitting (like a stock GN) and then line splits and goes into brake cyclinders. I know others have used this set up and PM set up with a Moser 9" and Wildwood brakes. I never thought to ask Moser if I needed a different brake/master cyclinder set up cause I didnt think it would be needed.

Thanks again guys.

[Red Regal T]

Really doesn't sound like a booster problem. Check booster as Steve suggested. Sounds like air in the system, poor adjustment, or bad master cylinder.

[Steve Wood]

No, Rick, I was trying to help Rich. I figured the Wildwood rears may take a different mastercylinder, and if he had a different mc, had he checked the function of both halves.

[Buicksx2]

Steve,

Shoot up to Jersey and gimme a hand......lol. We can hook up with Ed Baker and the boys and go to Etown and maybe visit the "other" RCA...........lol.

Thanks again guys.