Power Steering Reservoir Cap Question for 94' 530i

[bmw530]

It appears my car has been losing power steering fluid through a hole on the powering steering fluid reservoir cap. There is a small hole located at the side of the cap where your hand fits to turn the cap and it looks like a vent. The ps fluid reservoir has been needing refilled every couple of days and some of the fluid has made it onto the engine cover and surrounding area, leading me to believe it came from this vented cap. Also, when I have removed the cap after driving, the fluid seems bubbly and I have noticed a mist inside the reservoir almost like steam. Does anyone have any similiar experience or know about the operation of the cap? Thanks.

[yaofeng]

Unrelated question to the cap. Do you know if your car uses ATF or Pentosin?

[bmw530]

CHF 11s

[joshua43214]

It is possible, but unsusual for the suction hose from the resevoir to leak air into the system, this air will compress and at engine shut down will expand and force the PS fluid out of the vent. Also check the PS oil cooler, its a looped pipe either between the condensor and radiator or in front of the condensor. make sure its not covered in leaves. The oil does need to be cooled or it will expand and leak out the vent as well.

Do you have self leveling? Make sure you are using the proper fluid as well. Also make sure the fluid is warm when you top it up, it will expand a fair amount when it warms up.

[bmw530]

Thanks, I will check the items you suggested. The car does not have self leveling. I have added fluid when it wasn't very warm, so this may be compounding my problems.