03 S60 brake booster and vacuum pump issue

radium2013 · Post by **radium2013** » 10 May 2019, 19:59

I've been doing some research on the brake booster and vacuum pump. I hope I can figure out what's wrong with my 2003 S60 AWD (YV1RH59H).

My question is: when I turn my key to position II without starting the engine, is the vacuum pump supposed to provide me with some vacuum? In my case, I can hardly push the pedal in contrast to normal braking when the engine is on.

Thanks for any tips and if you want to see what happened to my car you can read the following.

There were twice when I pushed the brake pedal while driving but the pedal was too stiff to move at all. Then I immediately pushed the pedal again and fortunately it worked. Other than that, the brake works fine when the engine is on though it feels spongy.

Post by **oragex** » 10 May 2019, 22:35

First make sure you have a pump down there, it's down under the air filter box, and you should see the switch attached to the front of the box as well. Start by looking at the switch, the plastic cover does break and fall. If replacing it, test the pump as explained here below.

If you have a pump, just by turning the key to POS II without touching the brake pedal, the pump needs not running if everything is fine, the booster should keep enough vacuum for several days/weeks. Now, if at same moment you depress the brake pedal, then the pump should run, because the booster is loosing vacuum to apply the brakes. If you don't hear the pump when depressing the pedal with the key in POS II, then possible the pump has burned out. You should be able to depress the pedal 2-3 times before it gets stiff. If when you get inside the car, before even turning the key, the brake pedal is stiff at the first touch, then there is a problem. Either the booster seal, or the pump switch - or both. Start with the switch but keep in mind the booster seal gets very soft after 15 years, and starts loosing more or less vacuum.

radium2013 · Post by **radium2013** » 11 May 2019, 08:42

oragex wrote: ↑10 May 2019, 22:35 First make sure you have a pump down there, it's down under the air filter box, and you should see the switch attached to the front of the box as well. Start by looking at the switch, the plastic cover does break and fall. If replacing it, test the pump as explained here below.

If you have a pump, just by turning the key to POS II without touching the brake pedal, the pump needs not running if everything is fine, the booster should keep enough vacuum for several days/weeks. Now, if at same moment you depress the brake pedal, then the pump should run, because the booster is loosing vacuum to apply the brakes. If you don't hear the pump when depressing the pedal with the key in POS II, then possible the pump has burned out. You should be able to depress the pedal 2-3 times before it gets stiff. If when you get inside the car, before even turning the key, the brake pedal is stiff at the first touch, then there is a problem. Either the booster seal, or the pump switch - or both. Start with the switch but keep in mind the booster seal gets very soft after 15 years, and starts loosing more or less vacuum.

That makes a lot of sense. I watched several videos of yours before I got here. Thanks!

Post by **oragex** » 11 May 2019, 12:29

Welcome. I'm working on replacing the booster seal 'in situ' this summer, so if you find this issue, I'll put a video with a DIY this summer

radium2013 · Post by **radium2013** » 12 May 2019, 15:52

oragex wrote: ↑11 May 2019, 12:29 Welcome. I'm working on replacing the booster seal 'in situ' this summer, so if you find this issue, I'll put a video with a DIY this summer

It will be great if you can demonstrate how to replace the seal without removing the booster and brake fluid container.

I also followed your diagnosis video. What I've found is:
(1) the booster lost vacuum within 60 seconds after I turned off the engine, which probably means the booster has a leak(seal or check valve I don't know).
(2) the vacuum pump is definitely not working since I got no vacuum when I turn my key to position II. (I also disconnected the pump switch and I found no difference while driving.)

I plan to first replace the vacuum pump and hope that will give me a little more vacuum. After that, I will try to mimic your video attacking the booster seal with or without removing the booster from the engine compartment.

Thank you.