Oil Filler Cap Leak

[andyf1140]

Has anyone else had problems with the oil filler cap leaking on the 2.0L 4 pot? I've had this a couple of times and can't figure out what is going on. I even bought a new cap which sealed well to start with but soon started to exhibit the same behavior. It also seems to affect the tick-over as well as liberally spraying oil over the engine bay

 

[mac27040]

are you sure its the cap and not a oil pressure issue ?

 

[mac27040]

could also be the crankcase ventilation hose is blocked or collapsed.

 

[andyf1140]

The CCV was recently changed for a genuine BMW item. This always seems to happen after the cap has been removed to top up with oil, or to remove the cam cover, the plastic cover that hides all of the wiring. It's been fine for a few weeks and then I removed it to clean up a small amount of oil that was under the cover last night and new it leaking really badly again. When it's done this before taking it off cleaning up the mess and putting it back on has "fixed" it... It seams like the cap is not fitting properly.

 

[synthedup]

could also be the crankcase ventilation hose is blocked or collapsed.

Hi Mac.

How could someone check to see if it is blocked?

 

[mac27040]

can you take a pic of underside of oil cap and hole it sits in.

 

[mac27040]

looks like your missing the bottom plate to the oil cap.

https://www.rmeuropean.com/Products/11127500568-MFG9.aspx

http://www.realoem.com/bmw/enUS/showparts?id=BZ12-EUR-06-2005-E85-BMW-Z4_20i&diagId=11_3179

 

[andyf1140]

Here are pictures of them before and after cleaning...

 

[andyf1140]

Ok, so I've bent the tangs on the filler cap so that they are applying more pressure and cleaned up the mess and now it's running smoother again. I also checked the there is a slight vacuum in the rocker cover using a plastic bag.

 

[R60BBA]

Ok, so I've bent the tangs on the filler cap so that they are applying more pressure and cleaned up the mess and now it's running smoother again. I also checked the there is a slight vacuum in the rocker cover using a plastic bag.

This is a common problem on BMW models in general.

It occurs because the rubber which sits on the bottom half of the filler cap perishes and subsequently allows a vacuum effect into the cylinder head. As a result, when the car is driven hard, oil pressure increases yet due to the perished rubber, the pressure cannot be contained, which ends in the oil pushing up and through the bottom of the cap.

In my case just cleaning the cap did not solve the problem and I was forced to buy a new one.

 

[andyf1140]

Ok, so I've bent the tangs on the filler cap so that they are applying more pressure and cleaned up the mess and now it's running smoother again. I also checked the there is a slight vacuum in the rocker cover using a plastic bag.

This is a common problem on BMW models in general.

It occurs because the rubber which sits on the bottom half of the filler cap perishes and subsequently allows a vacuum effect into the cylinder head. As a result, when the car is driven hard, oil pressure increases yet due to the perished rubber, the pressure cannot be contained, which ends in the oil pushing up and through the bottom of the cap.

In my case just cleaning the cap did not solve the problem and I was forced to buy a new one.

Thanks that's reassuring