V40, 2004, Brake Booster or Vacuum Hose

dsilber · Post by **dsilber** » 18 Mar 2009, 08:30

I have a problem with my 2004 V40's brakes that has confounded 2 mechanics, so I thought I would bring the question to the experts.

When I back out of my garage, I push the brake pedal so as not to run over anything. On most mornings, the pedal is as hard as a rock and hardly moves. Even pushing with all my strength, the car continues to roll backwards. This happens for the first few times the brakes are applied, and seems to occur only after the car has sat for more than 10 hours and when it is colder (below 50F).

The Volvo dealer said that nothing is wrong with the booster (which is covered under warranty), and that nothing is wrong with the pads, calipers, etc. Only after I asked them to look at the hoses around the booster did they say that the hose needed to be changed (not sure which of the hoses they meant, but I think it is the relay hose). I had the car there 3 times and each time they couldn't get the problem to repeat, so it took some convincing on my part to get them to check different things. In short, I'm fairly certain that they diagnosed the hose to placate me - and because it is not covered under warranty.

My neighborhood mechanic looked at it and didn't find anything wrong with the hoses (after the typical spray with carbuerator fluid). What makes him think it is the booster is the fact that the problem goes away with a few brake applications (i.e., a leaky hose would always leak).

Any suggestions on a diagnosis? Thanks in advance.

cmj912 · Post by **cmj912** » 23 Apr 2009, 09:02

I wanted you to know that I have had exactly the same problem. One fine day, the dealer told me that my brake booster was not functioning correctly (unbeknownst to me) and that it needed to be replaced under warranty. That was fine with me.
After that, I noticed that even though the pedal feel was a little more "normal", I began to have the problem where if the weather was cold and the car had sat for 10-12 hours, the first two depressions of the brake pedal felt almost as if the pedal wasn't working at all.
Two different Volvo dealers and one independent mechanic have noted nothing wrong with the car. No leaks, no sensors, and the booster is performing normally. Still, as the weather warms I note that I don't have the problem as often if at all.
Still, it freaks me out, and what I am hoping is that one time when the car is in for service it will do it for them. Bringing it in expressly for that problem gets me simply shrugs and "there is nothing wrong with the car".
They say the same thing about the occasional upshift flare that the car exhibits, but I've learned to live with it...

dsilber · Post by **dsilber** » 23 Apr 2009, 09:17

Thanks for your reply. Now that the weather is warmer, my brakes have been fine, too. It is comforting to know that I'm not the only one with this weird problem. If I ever get it diagnosed and fixed, I'll let you know.

My V40 hasn't had the upshift flare, but the 2002 S60 does that every so often - the car is great otherwise, so I've learned to live with that quirk, too.

dsilber · Post by **dsilber** » 24 Jan 2010, 12:36

I bought a brake booster on ebay and had my neighborhood mechanic install a new vacuum hose piece (the little plastic part that sticks out of the brake booster unit). It has been fine ever since. I also saved about $130 US by circumventing the dealership.

Post by **OEMVolvoParts** » 25 Jan 2010, 08:50

There is a brake vac. switch that is a common failure. We hardly ever sell an entire booster for these cars, but we do sell the switch like hotcakes. There is a vin break for the part number but either way they are almost exactly the same part. For the late -04 car it would be pn 30620958. Check this part carefully before you go to the booster for your problem.