Engine revs when press brake

[IIA]

I noticed today that when I press the brake pedal in my 1970 IIA, the engine revs higher. As soon as I release the pedal, the engine slows again. I'm not sure if it's related, but recently I've also started to get a strange creaking sound when I press the brake. Any idea what could be going on?

Thanks.

[stomper]

You need to replace your vacuum booster.

[IIA]

OK, confession of ignorance. What's a vacuum booster?

[east high]

http://image.ec21.com/image/bbpbrakes/oimg_GC08045095_CA08046160/Brake_Vacuum_Booster_Assembly.jpg

It's the big black thing in this photo.

[IIA]

Got it. Thanks.

[Revtor]

(probably)
your brake booster, servo, whatever you want to call it is what takes your engines vacuum and turns it into "power" brakes. It's the only thing that connects your brakes and engine and so logically it's causing the problem. Sounds like the diaphragm or something inside the servo has gone south so when you hit the brakes, you get a vacuum leak and weird revving.

OR your boots are too wide and when you hit the brake pedal you are also hitting the gas pedal. haha

~Steve

[Contractor]

(probably)
your brake booster, servo, whatever you want to call it is what takes your engines vacuum and turns it into "power" brakes. It's the only thing that connects your brakes and engine and so logically it's causing the problem. Sounds like the diaphragm or something inside the servo has gone south so when you hit the brakes, you get a vacuum leak and weird revving.

OR your boots are too wide and when you hit the brake pedal you are also hitting the gas pedal. haha

~Steve


Yep, I actually have the opposite problem but the only logical thing would be your servo. Mine actually kills the motor when the brakes depressed and I assume it's a faulty diaphragm.

Anyway, swap that out and you should be good to go.

[mearstrae]

Look the situation over carefully, it may be a bad vacuum hose or connection, not the booster (servo) itself. And a vacuum test gauge is a helpful thing in the toolbox, good for several things.

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'76 Series III Hybrid 109
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