Booster leak causing increased idle speed?

DV8

Amateur Racer
Nov 14, 2005
134
0
0
Bucyrus Ohio
When I depress the brake pedal it causes a hiss from the booster and the engine idle increases a couple/few hundred rpm.

I just installed ALL new brake lines & hoses (rust damage & age) and everything bled out nicely with a real good pedal. The booster seems to be working ok, pedal is not heavy.

I've had boosters fail before, but they always gave a real heavy pedal and killed the engine......
 

81classic

Top Fueler
Jun 5, 2003
2,833
0
0
North Port, Fl
thats generally what happens when you get a vacume leak
 

JRodS79

Pro Stocker
Nov 28, 2005
1,567
0
0
kansas city mo
it may be about to let go but if you pump any booster fast it will increase idle. it may have a small vac leak and making it hard to come back to idle
 

DV8

Amateur Racer
Nov 14, 2005
134
0
0
Bucyrus Ohio
Well guys, did some more screwing around with the heap, and found the problem.

Under the dash, below the brake light switch, is another switch w/ a purple wire and a pink w/black tracer wire, AND A VACUUM LINE attached. I don't know what this is for exactly, but when the switch is activated (when the pedal is depressed) the switch starts leaking vacuum and the idle increases. No idea where the wires go (they dissappear into the harness) but the hose is connected to a T in the PCV hose.

This car was originally a diesel, had a truck 350 swapped in before I got it, but no sign of a hydraboost. Also has what might be aftermarket cruise on it? Car has buckets/console, PW PL PS PB.

I put visegrips on the hose, and no hiss and no idle change. But what is this switch for?
 

WEBBER

Pro Stocker
Apr 25, 2004
1,828
0
0
80 miles west of Joliet IL.
That switch would be for the cruise control. It kicks the cruise off when you hit the brakes.
 
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