1989 740 brakes make the engine idle faster

Tiger17 · Post by **Tiger17** » 17 May 2009, 18:44

Hi,

I've got a problem with my brakes on a 1989 740 wagon.

When I press on them they make a compression noise, which is a bit like a hiss, and that's fine, they've always done that. But when the pedal is depressed fully they continue to make that hissing sound, and they make the engine idle about 200-300rpm faster, or 300rpm slower (although it only did this once - and the poor car almost stalled!) The brakes still work like normal, so the increase in revs doesn't move the car, but I'm unwilling to drive it because I don't know what's wrong.

Does anyone have any ideas?

Cheers

DeRail · Post by **DeRail** » 17 May 2009, 21:57

Hi Tiger17, welcome to Matthews Volvo Site!

It sounds as if you may have a vacuum leak somewhere. Check all vacuum connections and make sure that none of the hoses have developed any cracks.

When you leave the car overnight and start driving in the morning do you notice the brakes hard to press lately? If so, it could be indicative of the brake booster leaking, or it could be a small valve on the booster that is failing.

Post back with questions or findings,
Darrell