My '87 240 wagon has developed a problem with the power brakes. If I have to jab the brakes hard and fast, it feels like there is no power assist. They feel Like power brakes, with the engine off, for a few seconds, then they finally get the power assist they need and work normal.

If I apply them gradual, in normal driving they wotk alright, although a little stiff as long as you don't apply them fast, and all at once. This can be dangerous, having the brakes very hard to push, in a panic situation. Could it be as simple as the one way valve in the vacuum hose, or is the booster going bad? What are the simptoms of a booster going bad?

Hello,

There are two different Brake Boosters ATE and Girling. The colors are Silver and Black. I had the same thing in my 1981 and could not figure out why the idle was rough, as well, until I had a Valve Adjustment at Volvo, who told me my Brake Booster was suspect. I got a couple sad looking ones from the Wrecking Yard. I removed mine. That was a Pain in the Butt to crawl under my Brake Pedal to remove the 4 Bolts. I took my Brake Booster apart. They more or less unscrew about 1/4 turn. Caution, there is a huge conically-shaped Coil Spring inside. And, once inside, those Black Parts also unscrew. What I found was that there are two very large Bakelite Plastic Discs with corresponding Black Rubber Diaphragms. I have been told that the Diaphragms tear. Maybe. They seem to be made out of the best rubber I have seen, but there does seem to be a lot of sticky goop inside. The rear Black Bakelite Disc had a 2" crack in it from the center radiating outward, thus leaking vacuum. The previous owner probably made a panic stop. I took the other Black Brake Booster apart. It was rusted and rough looking. I removed the bits and pieces I needed. Put it all back together again. For $10 a Brake Booster overhaul shop compressed the two halves together and told me it seemed to hold vacuum, fine, because that is what they use to help get the two halves together.

So . . . Brake Boosters can be repaired, like most other parts on your cars.

you are describing the symptoms.

there is one thing you can replace to see if it would make things a bit better (see below), but Boosters are non-servicable and if they go, there is no going back.

To me it sounds like you have a leaking diaphram in your booster, but try replacing your check valve and your hose (if it is hard or cracked). It may just be a leaking check valve, but you will only find out if it is the booster or not if you replace the check valve.

good news, if you need a booster, just swap the check valve to the new one.

good luck
Chuck in mpls.
--
'87 BMW 325e 190K (used to feed a '84 245, '88 244, '84 244, '85 744)

cbremski,
Thanks for the fast response. I do have a spare check valve on an old parts car(a 1980 240 that I drove for 23 years!!!!). Is it much of a pain to change out the booster? I have two spares, still on the car.

Thanks,
Jeff