D5 (D5244T to 2005) Oil filler cap popping noise

[Povo]

Hi all,

My XC90 seems to be having the famous oil filler cap popping noise. I vacuum tested the engine mounts and one of them is leaking vacuum.

I blocked off the vacuum line to the engine mount but it didn't make the popping sound disappear.

I have vacuum tested every single hose in the vacuum system - from vacuum pump to T junction to the boost solenoid and engine mount solenoid and there is no vacuum lost.

I disconnected the hose the T junction that goes directly to the vacuum pump and tested it and it's also fine but I cannot get rid of the noise.

What else could be causing it?

This is what it sounds like:

+ YouTube Video

[GrahamBrown1]

I to have this on my v70 and am yet to find the cause, hopefully someone will
Be along with a possible answer

[cheshired5]

It's a vacuum/air/boost problem.
So mounts, tcv, boost solenoid diaphragm, intake hose, turbo to i/c hose etc.
My noise was identical but it's now silent and in my case it was solved with new engine mounts and removing, cleaning and reseating the turbo to i/c connection.

[5cilinder]

If there is no leak it should be silent.
But the vacuumpump itself could also be leaking , the popping noise is just air discharge in the valvecover, so if besides of the leaking in the pump internally the vacuum externally is sufficient for the mounts etc ,then i shouldnt worry

[Povo]

Originally Posted by 5cilinder

If there is no leak it should be silent.
But the vacuumpump itself could also be leaking , the popping noise is just air discharge in the valvecover, so if besides of the leaking in the pump internally the vacuum externally is sufficient for the mounts etc ,then i shouldnt worry

That's what I was thinking but I wanted to be sure and check the vacuum line running to the brake booster but I cannot get the line off at the vacuum pump end. No matter how hard I squeeze it, it doesn't come off

[cheshired5]

Originally Posted by Povo

That's what I was thinking but I wanted to be sure and check the vacuum line running to the brake booster but I cannot get the line off at the vacuum pump end. No matter how hard I squeeze it, it doesn't come off

With engine off, pump your brake pedal until it is solid.
Keep your foot on the brake pedal and start the engine.
Your foot and pedal should start to sink.
If it does sink, your vacuum pump is almost certainly fine.

DON'T LET THE PEDAL GO ALL THE WAY TO THE FLOOR WITH THE ENGINE RUNNING.

[zork]

"DON'T LET THE PEDAL GO ALL THE WAY TO THE FLOOR WITH THE ENGINE RUNNING."

Could you,please,explain why?Thanks...

[blueacid]

Originally Posted by zork

"DON'T LET THE PEDAL GO ALL THE WAY TO THE FLOOR WITH THE ENGINE RUNNING."

Could you,please,explain why?Thanks...

The rubber seals in the brake master cylinder will be dragged over the (presumably rough) inner wall by the bottom of the master cylinder. This knackers the seals, and ultimately wrecks the brake master cylinder.