240 DL intermittent power brakes

billhamel · Post by **billhamel** » 19 Jul 2004, 10:54

Hi, and Yes it is rather scarey at times.

Anyway, I recently came into a 240DL Wagon and it was given to me mostly because of an intermittent brake problem. (no jokes please)

Basically what happens is that if I am in traffic on and off the brake suddenly it feels like there is no power assist on the brakes. Just like if you were to turn the engine off and start pumping the brakes - once tha vaccum is gone that is the feeling.

A brake booster was replaced before I got it and didnt fix the problem.

I think this is a vacuum issue since when I go up a long incline my defroster vents shift from defrost down below where the heating mode usually is. Typically this to me is either a vacuum tank, tank valve or leak somewhere. Maybe this is a secondary nonrelated issue to...

I am not familier with Volvo that much. But I looked around for a vacuum tank thinking it may have a leak, but couldnt find one.

I also see that some Volvo's have a vaccum pump but am at a loss if this is directly associated with the brakes or not since it is labeled like it something for the EGR system.

Any input greatly appreciated.

Thanks in advance
-bh

ozzimark · Post by **ozzimark** » 19 Jul 2004, 13:36

yeah, it's highly likely that you have a vacuum leak... although they can occur in a lot of places, so i can't give you any advice on where to start lookin...

Guest · Post by **Guest** » 19 Jul 2004, 13:43

Hi,

Well, I guess I should have said that it idles smoothly, you'd think a leak that big would cause a vaccum leak .....

ozzimark wrote:yeah, it's highly likely that you have a vacuum leak... although they can occur in a lot of places, so i can't give you any advice on where to start lookin...

ozzimark · Post by **ozzimark** » 19 Jul 2004, 16:13

hmmm.... true. maybe something is blocking/pinching the hose that goes into the brake booster?

LaRy · Post by **LaRy** » 20 Jul 2004, 12:55

At the hose when going into the booster you will find a valve letting the vacuum through in just one direction. I think this valve is leaking. The vacuum differs a lot in an engine, depending on how much you press the pedal compared to the torque you need. This is one reason why the brake booster has a one way valve, the booster will in this way also work as a vacuum tank when the vacuum in the engine is less than in the booster. If I'm not wrong it has normally the capacity to make five brakings without getting new vacuum from the engine intake. If this valve is leaking, you just have the vacuum existing for the moment, sometimes good, sometimes less good.