Hi all, and thanks Anth for the detailed reply.
It's now fixed. I installed a new booster though there was a bit of a journey getting there. I swapped the seal as I mentioned in an earlier post but after spending a day on it, there was no difference to the hissing sound. The booster was shagged so I bought a new one from an eBay store in Lithuania. It was exactly half the price of a new one from Volvo dealer in my city and while it does not have Volvo stickers on it, old and new are both Ate brand.
Removing the booster from the d5 XC60 is fairly easy. The engine does not need to get dropped. Here's a picture of the engine before pulling anything apart to show what type I'm working with in this scenario.
![Image description](https://cdn.ozvolvo.org/assets/files/2024-05-19/1716118811-953011-img20240518110055.jpg)
Picture under the dash after removing trim panels but before I pulled anything brake related apart. The white pin attaching the booster to the brake pedal needs to be removed. It has little clips at the bottom of the shaft but it just comes out with gentle but persistent levering of the head with a screwdriver. The four bolts around the bellows need to be removed with a 14mm deep socket and about 40cm extension. I was also able to fix a really annoying squeek that occurred every time the brakes were applied by lubricating the two switches on the brake pedal located close to the accelerator pedal, one is the brake light, not sure about the other
![Image description](https://cdn.ozvolvo.org/assets/files/2024-05-19/1716119392-35844-img20240518110211.jpg)
In the next picture I'm showing the extent of what needs to be removed to allow enough space for the booster to come out.
Wiper cowl
Just remove the six clips and the windscreen wipers, and the side pieces in the lower windscreen corners
The sound deadening firewall
Just the 2 x 8mm bolts in front of the booster are enough to allow the metal panel to move forward by about 40mm giving enough clearance for the booster to come out. It is not necessary to remove the entire panel.
Windscreen wiper assembly
There are 3 x 8mm x 40mm long bolts to remove. Also undo the electrical connector and move the wiper assembly out of the engine bay
Master cylinder
Unbolt the master cylinder from the front of the booster and move it well out of the way. Conveniently Volvo build in a short section of flexible brake lines to allow this.
Vacuum hose
The vacuum hose just pulls out. There are no sensors in this booster, the xc90 and v40 have 2 sensors but the XC60 gets pedal pressure and speed from somewhere else.
In the picture below, I'm pulling back the metal panel about as far as it needs to to provide enough room for the booster to come out
![Image description](https://cdn.ozvolvo.org/assets/files/2024-05-19/1716119335-140119-img20240518113754.jpg)
Here is the old booster out of the car.
![Image description](https://cdn.ozvolvo.org/assets/files/2024-05-19/1716120717-64123-img20240518114944.jpg)
I took a look at the old booster to see where the problem was and a crack is quite obviously in that plastic piece. The new booster looks to have replaced that with metal. It's very frustrating that Volvo/Ford would use such poorly designed product that is designed to fail. I've had older cars where the booster is over 40 years old and it's never misbehaved. In may respects we are going backwards with our cars.
![Image description](https://cdn.ozvolvo.org/assets/files/2024-05-19/1716120808-163645-img20240518115402.jpg)
New booster compared to old booster
![Image description](https://cdn.ozvolvo.org/assets/files/2024-05-19/1716121029-155257-img20240518115114.jpg)
![Image description](https://cdn.ozvolvo.org/assets/files/2024-05-19/1716121071-610962-img20240518115154.jpg)
The job took 2 hours going fairly slowly to swap the booster after the practice run a fortnight earlier that was unfortunately a waste of time.
It's great to be able to enjoy driving the car again without the incessant hissing