06 S60 R non-responsive brake pedal at startup Topic is solved

[oragex]

I had to change the brake pedal position sensor in the brake booster (I didn't change it with the brake booster a year ago). This helped and the system now holds vacuum for the whole night.

If I'm not wrong, I think it's called a brake booster diaphragm position sensor. It had a small seal and needs be seated properly or it won't seal. Pretty tricky to seat this sensor, needs be pushed quite firmly before the retaining clip it's engaging and locks it in place.

[oragex]

So, is the seal gone too, based on the whoosh sound and the black marks?
Video.MOV

Yes, those are the two symptoms. New seal if you want to try replacing it (eBay item number: 253648287399). Someone said he replaced the seal with the booster in place and skin damage but I think it's quite tricky. Removing the booster needs 3/8" wobble, 2-3 long extensions, 13mm deep socket, and a powerful corded drill to turn the nuts: these are secure nuts really hard to turn with the ratchet. I'm working on a DIY video on this.

I suspect the pump is also gone by now. You can undo it's connector and plug it to the alternator (red cable) with a long wire, second wire to a ground nearby (engine off). When removing the pump, it's attached with some tricky bolts and bushings - I actually remove it with the whole bracket (see it at 5:30). Used one should be fine if tests good.

[zjevik]

I had to change the brake pedal position sensor in the brake booster (I didn't change it with the brake booster a year ago). This helped and the system now holds vacuum for the whole night.

If I'm not wrong, I think it's called a brake booster diaphragm position sensor. It had a small seal and needs be seated properly or it won't seal. Pretty tricky to seat this sensor, needs be pushed quite firmly before the retaining clip it's engaging and locks it in place.

That name would actually corresponds to what the sensor does but they call it brake pedal or brake booster position sensor (https://www.ipdusa.com/products/16513/1 ... ion-sensor, https://www.fcpeuro.com/products/volvo- ... o-31687032). The sensor went bad and the cruise stopped working so replacing it was no brainer for me.

[zjevik]

...

Side note, the booster starts leaking slowly but enough to engage the pump - this can last for years causing the pump to wear out then as mentioned there may be no more boost at a cold start. Perhaps the original poster can check the booster at the seal near the pedal by tossing the grey dust boot, if the white plastic tube has black marks on it it means the seal is damaged
...

So here is a video just taken of my car. Is the seal gone too, based on the whoosh sound and the black marks?

The seal looks pretty bad but here is how mine looks and sounds: https://photos.app.goo.gl/LW86tuS87bqk3jUt2

The brake boosted is about a year old and you can hear the vacuum pump whining in the background.

If I was in you I would order the pressure switch, pedal position sensor and the vacuum pump if you already checked all the hoses. Make sure to inspect the portion of the hose under the air filter housing. I would try to change the switch first (10 minutes job) if that doesn't help then you should do the pump and/or the pedal position sensor. If the switch helps you then you can return the rest and be done.

[oragex]

That name would actually corresponds to what the sensor does but they call it brake pedal or brake booster position sensor (https://www.ipdusa.com/products/16513/1 ... ion-sensor, https://www.fcpeuro.com/products/volvo- ... o-31687032). The sensor went bad and the cruise stopped working so replacing it was no brainer for me.

Great info with the cruise control relation

[oragex]

...

Side note, the booster starts leaking slowly but enough to engage the pump - this can last for years causing the pump to wear out then as mentioned there may be no more boost at a cold start. Perhaps the original poster can check the booster at the seal near the pedal by tossing the grey dust boot, if the white plastic tube has black marks on it it means the seal is damaged
...

So here is a video just taken of my car. Is the seal gone too, based on the whoosh sound and the black marks?

The seal looks pretty bad but here is how mine looks and sounds: https://photos.app.goo.gl/LW86tuS87bqk3jUt2

The brake boosted is about a year old and you can hear the vacuum pump whining in the background.

If I was in you I would order the pressure switch, pedal position sensor and the vacuum pump if you already checked all the hoses. Make sure to inspect the portion of the hose under the air filter housing. I would try to change the switch first (10 minutes job) if that doesn't help then you should do the pump and/or the pedal position sensor. If the switch helps you then you can return the rest and be done.

I'd say the seal is gone. The black stuff is actually seal material. This seal needs a very specific grease over the white cylinder, silicone-teflon stuff

https://www.ebay.ie/itm/MERCEDES-W163-M ... Swt5VbCLo8

https://www.ebay.ie/itm/Lubricant-TF-Gr ... SwsFVaqY0b

[jimmy57]

The highest likelihood is vac pump since the OP says they are good after a few minutes. Even a leaking booster is usually overcome by the pump vacuum capacity. The dual cvvt engines have very little vacuum until engine temp warms a bit. There certainly is the chance that it has a booster issue too. Some booster leaks are worse until engine compartment warms and hardened seals soften.

[erikv11]

So I pulled the vac pump and it is dead, 12V will not make it go. And as jimmy57 points out everything is fine after a few minutes, so I will assume the pump switch is OK, that everything else is OK. At this point the likely summary is

- booster seal went bad
- bad seal overworked the pump, and the pump died.

Went to the junkyard to get another pump and ... closed for the holiday weekend.

I think I will put in another vac pump so my wife has brakes at startup, while I make plans to pull the booster and replace the seal. The seal repair is not going to happen right away, though.

[oragex]

I suspect the pump was killed by the old booster, it's just a back up vacuum pump specifically for cases when there's a leak at the booster

[jimmy57]

They fitted electric vacuum pumps due to low vacuum when the cam timing and ignition timing are adjusted for catalyst and engine coolant warming. The settings that accomplish these goals lowers manifold vacuum a lot. Altitude lessens manifold vacuum even more. Audi, VW, BMW , MB, Foed, GM, FCA, etc., etc. fit electric and now mechanical pumps for the same reasons.
I don't see brake booster failures on Volvos being any worse than other brands. The fact we keep cars longer makes brake boosters showing up on the list more likely.