brakes work but booster for them doesn't on 1994 850 wagon

Chasma · Post by **Chasma** » 21 Jun 2018, 15:55

When I brake while driving, the booster starts, but gives out almost immediately, so I have to basically stomp on the pedal to actually stop. I tested the hose going to the booster, there's no leak. If I start the car with the brake pedal held down, it drops like usual, but a second or so after it drops further again lower than it seems like it should.

Post by **scot850** » 21 Jun 2018, 16:11

There is a valve in the booster which holds the vacuum pressure. I'm not sure exactly where it is on 94, but on later cars it is fitted on the front of the booster where the pipe from the manifold connects. There is a chance the booster diaphragm can also fail, but I would check the simpler things first. The valve is not expensive, but if you have a junkyard nearby try pulling one but do check they are the same as I have a recollection they changed somewhere along the line.

Also really carefully check the pipe from the manifold to the booster, they go hard and split with age, and sometimes finding the failure part can be hard to do.

Neil.

MDK · Post by **MDK** » 21 Jun 2018, 17:57

Hey there Chasma.. MDK here. There are several things to check for when you have what your describing. First... how's the brake fluid level? Is there any sign of leakage at the wheels or the brake lines themselves? I've seen master cylinders actually leak internally and actually have brake fluid in the brake booster and there by rotting out the brake booster. If you're mechanically inclined, they are not too hard to change. I suppose you could buy one from salvage yard for about 20-30$ as a new one would be very expensive. I would get a friend to help check out the entire system with a good strong flashlight... I wouldn't drive it until I knew what is going on... hope this helps..MDK