Brake Booster Vacuum Switch #31400608 Top Popped Off

[wanderdüne]

Hi, I'm cross posting this here:

Funny story. I just moved my snow tires over to my 2004 XC90 2.5T because the vacuum pump on my 2003 XC90 T6 was running steady for several minutes after the ignition was switched off. It also ran several minutes when the key was turned on (brake pedal not depressed). Went out this morning to compare the two systems and found that the top of the switch on the 2004 2.5T is popped off, revealing the spring inside. Looks like the pump on that one has seized; didn't really notice because it has been driven sparingly since I got it while I a rehabbing the suspension. Delicious irony in that I moved the tires over and then found an even worse issue on the same system.

Anyway, looks like I will be ordering at least one new switch and one pump. A couple of questions first.

-What are the ramifications of running the vehicle in this condition and how does it affect the vacuum in the three lines that run off the switch?

-On the 2003 T6 with a working pump: What is a good test procedure to find out where the leak is coming from? Looking for kind of a walk-through.

Both vehicles have (minor) booster diaphragm leaks. There is no constant hissing however, and at least in the 2003, the pump comes on steady without the brake pedal being depressed.

Thanks

[abscate]

The leak should are more likely in the hoses the switch than the booster itself.

You can get a leak at the master cylinder sleeve on the V70 chassis, I’m guessing the XC90 is similar

You can replace that switch with hand tools and it’s important to do so. The vacuum pump is a low duty cycle design so if it’s running constantly it will burnout.

...you rock for putting part number in title by the way.



$80 from cheapest source I quick scanned , plus shipping

$90 shipped from FCP with lifetime warranty. You don’t get to use the warranty across multiple car stuff though, that’s rude.