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

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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Year and Model: 1994 850
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brakes work but booster for them doesn't on 1994 850 wagon

Post by Chasma » Thu Jun 21, 2018 3:55 pm

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.

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

Post by scot850 » Thu Jun 21, 2018 4:11 pm

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.

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

Post by MDK » Thu Jun 21, 2018 5:57 pm

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

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