Bad booster? (brake pedal comes up hard at shutdown)

[hooziewhatsit]

This is my BILs '94 Loyale.

 

I haven't noticed this on any other cars I've driven, which makes me think his brake booster may be bad.

 

Whenever you turn the engine off, the brake pedal comes up pretty hard under your foot. It comes up enough that you'll start to roll unless you really push it back down.

 

Before turning the engine on, pumping the pedal brings it up pretty hard, then after turning the engine on the pedal goes down a bit, like it should.

 

Otherwise the brakes are a bit spongy, but that's probably because they need bled (yet) again. He has to add 1/2" of fluid every few months I just replaced the rear wheel cylinders, which had seen better days, so that should help I hope.

[presslab]

It might be the check valve located inside the booster hose.

 

Pull the hose off the booster and see if it holds vacuum with a MightyVac. Then use the MightyVac to make sure the check valve is tight.

[hooziewhatsit]

Are you sure there's a check valve in the hose? I sure don't see one.

 

In other news, I really need to get a mityVac one of these days

[presslab]

Are you sure there's a check valve in the hose? I sure don't see one.

 

In other news, I really need to get a mityVac one of these days

 

Yeah there should be one inside the hose. You can't see it, maybe a little lump, but if you squeeze the hose you'll find it. Unless it's missing, and that's your problem. :-p Sometimes there is a bit of white paint where the valve is. On some models I believe the valve is located at the fitting on the booster.

 

In any case you should be able to pull the hose off the intake manifold, suck on it with your mouth, and it should hold the vacuum.