Engine Almost Stalls When I Pump The Brakes (1 Viewer)

[GRM]

I'm trying to resolve a myriad of braking problems with my '86 which has been holding me back from driving it more.

One item I can't figure out, is that when I pump the brakes at idle, the engine RPM's drop to ~400, nearly stalling the engine.

Any ideas what might be going on?

 

[snobdds]

Where in the intake are you pulling vaccum for the booster? Is the hose and check valve good? Also, what's your warm idle set at?

 

[Mudder]

I second that it sounds like either the brake booster check valve or a cracking in the hose going from the booster to the intake manifold.

 

[KoffeeKommando]

You have a bad brake booster. Just went through this on a friends 1986 truck.
His check valve and hoses were perfect.

Everybody +internet will only tell you of the "hard pedal" brake booster failure mode.

Pay attention to what this guy says in beginning of video. His 1994 yota truck had exact failure mode as yours and my friends. None of the related videos on YT even hint at the "engine stalling" brake booster fail mode. It's weird that nobody mentions a failure like this. They all talk about the "textbook" hard pedal problem or hissing from pedal area.



Bonus...here is what a bad booster looks like internally: