My XC90 has had another weird problem which I couldn't find much info on, because I didn't know what to search for. Both driver and passenger seats developed a hiss noise that would cycle on and off over a period of a few minutes. It wasn't all that loud, but was audible under normal driving conditions. After poking around under the seat, I could see that there was a little tube that had cracked on both sides. I wasn't sure what it did, because I don't use the seat massage function, but my wife does though strangely she wasn't complaining that it didn't work any more.
It has been repaired for about $10 and is good as new. I've used 6 x 4mm Polyurethane (PU) tube from AliExpress, a few cable ties and some fabric tape. The seat massager seems to prime itself when the car is first started, when it can't get to pressure because the pipe is cracked, it keeps on trying to pressurise continuously.
The process involved
1) Remove each front seat, FYI XC90 seats must weigh 40kg, they are extremely heavy. The front bolt covers are easy to remove, press down with a finger on the springy plastic bit and slide forward. The rear ones need a little screw driver inserted into a small hole so that the retaining clip is moved, then they slide rearward. Undo the 4 bolts in each seat using a 13mm socket. I didn't undo the seat belt, just sitting the front seat on the back seat is enough, though put down cardboard or similar to prevent the sharp front seat brackets damaging the car. Undo the 3 small plugs, the one big plug (loosen the 7mm retaining bolt) and the air tube
2) Remove the door scuff trim and the little plastic cover bit bottom of B pillar
3) For passenger side, remove the trim retained by 2 x torx that sits below glove box
4) Remove the trim on the side of the transmission tunnel (or whatever it's called in a transverse engined car)
5) Remove the bonnet catch, there's one 8mm bolt
6) Remove the carpet/foam base from each side of the car. With all the trim pieces removed it will just lift up
7) Locate the air pump bag , unplug the electrical connector and release the little retaining clips holding it to the seat frame base thing. The pump can now be removed from the car.
8) Cut the cable tie holding the pump bag closed, remove the pump
9) Unwind the cloth tape, free the wiring, remove the quick release hose barb end and take the pipe off the pump. Note the length of the old pipe and cut the new pipe to match. The old pipe has a spring inside to prevent collapsing under a vacuum. Pull it out and slide it back into the new pipe.
9) Rewrap the wiring and the PU tubes. Reinstall in the pump bag and replace the cable tie
10) Reinstall everything back in the car.
Hope this helps someone
Pictures below:
