2007 S60 Vacuum Boost Operation Issue

BET76 · Post by **BET76** » 06 Apr 2021, 18:50

Volvo wizards - My 2.5T vacuum boost pump runs (buzzes loudly) for 1-2 seconds every time I step on the brake pedal. This happens whether the car was just started or has been driven for many miles. Twice the past year, it started buzzing and wouldn't stop until I cut off the engine. The brakes feel fine and work well. To troubleshoot I disconnected the switch's electrical plug in front of the air filter, and the pump never ran - as expected. I reconnected it and it went back to buzzing on every brake pedal press.

Suspecting a faulty switch or just to remove an old part that sometimes fails, I replaced it with a new Volvo one, but this made no difference. I'd appreciate your advice on what to check or test next. I've searched through the forum, but haven't found a match for this issue. If I missed it, please point me in that direction. Thanks!!

Post by **jonesg** » 07 Apr 2021, 00:13

vacuum leak?

BET76 · Post by **BET76** » 08 Apr 2021, 17:25

Thanks, jonesg. I'll start there.

Post by **firstv70volvo** » 08 Apr 2021, 18:00

Sounds like it could be the brake booster pushrod seal. This is the brake booster seal inside under the dash and it's the rod connecting the brake pedal arm to the brake booster. There's a large diameter white collar as part of the this rod and the seal seals vacuum in the booster around this white sliding part. With the engine running you should listen carefully for a hissing sound under the dash when the brake pedal is pushed and released and also listen when the engine if first shut off as the brake pedal is pressed and released.

BET76 · Post by **BET76** » 05 May 2021, 18:36

Thanks for the suggestions! I just got access to the car and listened to the booster on the firewall above the brake pedal. When I start the car and press on the pedal, I hear a whoosh or hiss sound each time as it moves. I assume I shouldn't hear any air noises if the seal is still working properly.

Looking at DIY fixes, I've found the new rubber seal online with instructions for replacing it with or without removing the booster. I'm fairly mechanical, but the stories of how difficult and awkward it is to replace the seal in-place are convincing me to remove the booster first. I'm not as young or thin as I used to be! Then, if I do that much work and have it out, I'm thinking why not replace the booster w/o the master cylinder with a new ATE one for under $200. I plan to keep the car for a good while. Thoughts??

Post by **firstv70volvo** » 06 May 2021, 10:52

BET76 wrote: ↑05 May 2021, 18:36 Thanks for the suggestions! I just got access to the car and listened to the booster on the firewall above the brake pedal. When I start the car and press on the pedal, I hear a whoosh or hiss sound each time as it moves. I assume I shouldn't hear any air noises if the seal is still working properly.

Looking at DIY fixes, I've found the new rubber seal online with instructions for replacing it with or without removing the booster. I'm fairly mechanical, but the stories of how difficult and awkward it is to replace the seal in-place are convincing me to remove the booster first. I'm not as young or thin as I used to be! Then, if I do that much work and have it out, I'm thinking why not replace the booster w/o the master cylinder with a new ATE one for under $200. I plan to keep the car for a good while. Thoughts??

If I were to do it again I'd do what you're thinking, buy a new ATE booster especially if you plan on keeping the car for a good while. Even a remanufactured booster doesn't replace all the parts I think should be renewed with a brake booster. Based on the experienced I had trying to replace this seal under the dash I would highly recommend not doing it this way. I'm impressed others were successful doing it this way but I still wouldn't recommend it.

Post by **KidsV70** » 11 May 2021, 23:56

+1 for firstv70volvo's solution.

I tried the rubber seal repair and failed. It's made by URO I think? I'm a decent mechanic, been fixing my own cars for ~30 years. I ended up buying the new booster. There may be others who know "tricks" to the fix.

Best,
Bert

Post by **chrism** » 12 May 2021, 09:11

If a person suspects a leaking brake booster is the cause of the vacuum pump running on it can easily be determined by disconnecting and capping the vacuum hose. If the pump still runs on then the leak is somewhere other than the booster.