Hello everyone, we bought a used 2006 XC90 2.5t awd for my wife about 2 months ago. So far it's been the perfect fit for our family but I've run into an issue with the brakes.
My wife first notice that the brakes were very hard to apply first thing in the morning while backing down the driveway. I replaced the pads, rotors and bled the system with all new DOT 4 fluid. Helped overall braking but still had the cold brake issue that she was complaining of.
Thats when I found this site. I read about the vacuum pump and associated problems with the sensor for the vacuum pump. So I tested everything from the fuse to the switch to the pump. The pump was not responding at all and the switch was not responsive to any tests I did. Ordered up a new pump, pump to switch line and switch. All of it arrived today and I installed it. Finally brakes feel much better.
How ever....I noticed that the pump seems to run ALOT. Start the car, hit the brakes and it runs. Start backing down the driveway and hit the brakes again, pump turns on. Come to a complete stop at a stop sign and I can hear the pump turn on. So two questions
1: is it normal to hear the pump over the motor? It's just seems excessively loud considering how quiet everything else is on this car.
2. Is it normal for it to run this much? Or should I start looking for vacuum leaks or a possible leak in the booster?
Sorry for the long winded first post. Thanks in advance.
XC90 Vacuum Pump
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jimmy57
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What is your altitude?
Does it do this as long as engine runs or just within the first minutes of engine operation from cold start.
Altitude and engine temp affect manifold vacuum made from a running engine. Altitude affects all engines and engines with variable valve timing do things with valve timing during engine warm up that reduces vacuum produced.
If the two things above are not causes then there is a check valve in the hose to intake manifold that is connected to brake booster. This same plumbing had the vac pump switch attached to it. The check valve could be faulty or gummed up and not allowing engine vacuum to go past it into the section of the hose where vac pump is attached and onto the booster.
Does it do this as long as engine runs or just within the first minutes of engine operation from cold start.
Altitude and engine temp affect manifold vacuum made from a running engine. Altitude affects all engines and engines with variable valve timing do things with valve timing during engine warm up that reduces vacuum produced.
If the two things above are not causes then there is a check valve in the hose to intake manifold that is connected to brake booster. This same plumbing had the vac pump switch attached to it. The check valve could be faulty or gummed up and not allowing engine vacuum to go past it into the section of the hose where vac pump is attached and onto the booster.
Altitude here is about 4,500 feet and temp has been mid 50's the past two days.
I drove the car around the neighborhood and got it up to normal temp and it still seemed to be doing it. My wife drove it to the store and back last night and said it still did it just the same.
I will check all the connections again tonight as well as the check valve. That's a great idea. It could be clogged and that's what caused the previous pump to fail. Thanks for the tips.
I drove the car around the neighborhood and got it up to normal temp and it still seemed to be doing it. My wife drove it to the store and back last night and said it still did it just the same.
I will check all the connections again tonight as well as the check valve. That's a great idea. It could be clogged and that's what caused the previous pump to fail. Thanks for the tips.
Update from tinkering after work tonight.
Checked the vacuum connections, everything seemed tight, including the connection at the booster on the firewall
Pulled the check valve out and looked it over, not overly gunked up but cleaned and tested it by blowing one end and sucking the other. Seems to be operational. Reinstalled.
Same results. Fire it up, pump turns on. Hit the brakes, pump turns on. Back down the driveway/hit the brakes, pump turns on. Drive down the street, hit the brakes, pump turns on.
No wonder the previous pump burned out if it was running this much.
Just for the heck of it, pulled the line off the check valve going to motor with the motor running. It has good vacuum. I don't have a vacuum gauge so i don't know how much, but it had vacuum.
Checked the vacuum connections, everything seemed tight, including the connection at the booster on the firewall
Pulled the check valve out and looked it over, not overly gunked up but cleaned and tested it by blowing one end and sucking the other. Seems to be operational. Reinstalled.
Same results. Fire it up, pump turns on. Hit the brakes, pump turns on. Back down the driveway/hit the brakes, pump turns on. Drive down the street, hit the brakes, pump turns on.
No wonder the previous pump burned out if it was running this much.
Just for the heck of it, pulled the line off the check valve going to motor with the motor running. It has good vacuum. I don't have a vacuum gauge so i don't know how much, but it had vacuum.
Quick update (I hate finding posts that have my exact problem but without resolution to it, So here is my findings)
After testing and deciding that my vacuum switch was bad. I replaced it.
Pump would not come on with new switch. Replaced it too.
Pump ran, switch seems to operate normally, but the pump would run every since time the brakes where depressed. Regardless of engine temp or time running.
Ordered replacement push fitting at the vacuum pump, replacement O-ring grommet for booster and replacement check valve.............and finally, we have what seems to be normal operation. Somewhere it was leaking vacuum and causing the pump to run excessively. Hopefully this fixes the problem from here on out.
After testing and deciding that my vacuum switch was bad. I replaced it.
Pump would not come on with new switch. Replaced it too.
Pump ran, switch seems to operate normally, but the pump would run every since time the brakes where depressed. Regardless of engine temp or time running.
Ordered replacement push fitting at the vacuum pump, replacement O-ring grommet for booster and replacement check valve.............and finally, we have what seems to be normal operation. Somewhere it was leaking vacuum and causing the pump to run excessively. Hopefully this fixes the problem from here on out.
Root causes:
The vacuum hoses leading from the intake manual have rotted out ($6 replacement) and bleed/ leak vacuum, thus triggering the vacuum pump system to make up lost brake boost vacuum.
The brake booster canister is leaking and no longer holds vacuum. Replacing it is a doable diy project where you spend a whole lot of time on four small, hard to reach, nuts inside the car under the steering wheel. If manifold vacuum cannot be maintained in the brake booster, the vacuum valve calls for the electric vacuum pump to make up the missing vacuum. This comes in handy if the car turns off and still needs brake power. It is also active for 10-15 minutes after you shut off your engine.
Most likely is that the vacuum sensor/switch is stuck between open and closed after you overpressurized what should be manifold vacuum when you used Turbo boost. And, if it cannot trap manifold vacuum in the brake booster, it calls for the electric vacuum pump to turn on.
When all is working properly, you rarely hear more than a few seconds of electric vacuum pump buzz. When its not working well, the buzz will continue for many minutes and the pump gets too hot to touch.
The vacuum hoses leading from the intake manual have rotted out ($6 replacement) and bleed/ leak vacuum, thus triggering the vacuum pump system to make up lost brake boost vacuum.
The brake booster canister is leaking and no longer holds vacuum. Replacing it is a doable diy project where you spend a whole lot of time on four small, hard to reach, nuts inside the car under the steering wheel. If manifold vacuum cannot be maintained in the brake booster, the vacuum valve calls for the electric vacuum pump to make up the missing vacuum. This comes in handy if the car turns off and still needs brake power. It is also active for 10-15 minutes after you shut off your engine.
Most likely is that the vacuum sensor/switch is stuck between open and closed after you overpressurized what should be manifold vacuum when you used Turbo boost. And, if it cannot trap manifold vacuum in the brake booster, it calls for the electric vacuum pump to turn on.
When all is working properly, you rarely hear more than a few seconds of electric vacuum pump buzz. When its not working well, the buzz will continue for many minutes and the pump gets too hot to touch.
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