Bubbling sound in the rear trunk

[dezpimpdada]

Hi all,

i recently noticed a strange sound when i opened my rear trunk to take out my computer bag. it sounds like something is boiling..........like a bubbling sound when you boil water. as i listen closely i noticed its coming from the oil cap. the sound is louder if i remove the oil cap. the car drives fine and engine is not over heating. i had the AOS replaced some 20k miles ago. car has about 104k now. i brought the car to the mechanic and he has no clue on what could have caused it. its only making that noise when the car is hot, after driving for a long time. does anyone know what's going on? i just want to make sure this is not something big waiting to happen. thanks

by the way, the engine is off

Paul

[wvicary]

Replace the coolant cap. It has been updated several times over the years.

[dezpimpdada]

the sound is coming from the engine oil cap and engine itself not the coolant area. as i listen closely its almost like a high pitch vacuum sound........

Replace the coolant cap. It has been updated several times over the years.

[Steve Tinker]

If the noise is actually caused by a strong vacuum and the oil cap is difficult to remove with the engine running, there's a good chance that your AOS is failing.

A faulty AOS is also usually accompanied by exhaust smoke on startup.,

[wvicary]

The coolant temp rises after you shut off the engine which can overcome a weak pressure valve in the coolant cap. It's cheap/easy to replace to see if that cures the fault.

[kbrandsma]

If your cap ends in 01, It should be replaced. I replaced mine last summer and I believe they end in 04 now.

[CarreraLicious]

Yep, they end in .04. Just picked one up to replace my cap ending in .01 even though I've had no issues.

[dezpimpdada]

i just checked the coolant cap and sure it was ending in 01......i will go pick one up and see if that fix the problem. i don't think and hopefully not another AOS issue since i had already replaced it once.

[dezpimpdada]

opened oil cap with engine running............there's some suction but not difficult to open. i think my replaced AOS is still holding ok. now all i have to do is to pick up a new coolant cap and hopefully its that easy.