Cavalier with bad booster?

[iwannadie]

Trying to figure this out and would appreciate any input.

2002 Chevy Cavalier LS automatic.

While stopped holding the brakes the engine stumbles and if held long enough or pressing hard enough on the brakes the engine dies. Being in different gears has no effect. I can't hear any obvious vacuum leaks anywhere other than a hissing while the brakes are held inside the car.

I pulled the vacuum hose from the booster and plugged it and the problem goes away. Replaced the check valve and it had no effect. No fluid loss that I can see.

Just trying to confirm the booster before pulling anything apart. I think by plugged the booster vacuum hose and eliminating the problem that has to narrow it down to the booster and not a leak some where else.

 

[Bryan C.]

Sounds like you got it narrowed down. By disconnecting the vacuum line you isolated the issue to the booster. Internal vacuum leaks aren't very common but they do happen from time to time. Get a new one and see what happens. If it were me I would shy away from junkyard parts and buy a new one, I'm not one to take risks with my brake system.

 

[iwannadie]

Forgot to add, the brake pedal slowly sinks to the floor. I was reading that a bad booster causes a firm pedal(I've never had a bad booster on any vehicle). The brake pedal feels to me like a bad master cylinder but I haven't had a bad MC cause the engine to stumble or die before like this. The squishy pedal makes me want to focus more on the hydraulic side...

 

[Talyn]

Master cylinder could be leaking into the booster. How is the fluid level? Any fluid in the booster vac line?

The pedal sinking could be the booster some what holding vacuum when the pedal is pressed. Similar to what happens to a normal system when the vacuum is bled off then you start it.

 

[GrimmJeeper]

I'd throw my 2¢ on the stack here and agree with Talyn, when the piston seal leaks at the back of the master cylinder it can leak brake fluid directly into the internals of the booster, then the rubber of the diaphragm rots out and starts to leak.

It sounds like you definitely have a booster problem, but you may want to look into replacing the master as well.

 

[N8N_99xj]

+1, what he said.

 

[iwannadie]

Thanks guys, I was just going to replace the booster and try not to disconnect the MC but it will make it a lot easier getting the booster out with the MC out of the way also so doing them both sounds like a good plan.

Oh, I didn't see any brake fluid in the booster vacuum line but that doesn't mean it wasn't there. I was looking at it in a parking lot late at night(not my car).