Filler cap oil leak - BEW Golf

So I've been fighting this silly oil leak around the filler cap for some time.

I already replaced the gasket with a brand new one, i even doubled up the gaskets just to make sure there's enough down pressure on the gasket to seal the oil (new one touching the head). That slowed down the leak, but didn't stop it entirely.

I normally wash out the head cover every time i change the oil, so that's how i know when it starts and how far it goes. I did notice that when i use the pedal a bit harder than usual, it tends to leak more - i would say anything over 3k - although it's hard to watch the leak as i'm driving.

The rubber collar fits snug around the neck of the filler hole, but doesn't seal it (don't think it's meant to).

Here's the cap with the leak around it - circled in red


This is the back of the engine as the oil moves down:



On a slightly separate note, the dipstick gets oiled somehow also ... no idea how, as there's nothing in front of it to blow oil on it the way the pattern suggests (just on that front face of it):


Here you can see what's in front of that dipstick



Any ideas on these, but especially the top filler cap leak?

Is it a high milage car? This could be blow by but I could b completely wrong

Mine's a low mileage BEW and it does the same thing (the cap, not the dip stick). I sort of ignore it...

04trd said:

Is it a high milage car? This could be blow by but I could b completely wrong

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I got 220 on there now. Maybe about half way through her life : -) but it's been doing it for a while. What's the blow by refer to?

BEEnTDI said:

I got 220 on there now. Maybe about half way through her life : -) but it's been doing it for a while. What's the blow by refer to?

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Crankcase pressure from combustion getting past the pistons.

El Dobro said:

Crankcase pressure from combustion getting past the pistons.

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If it is that - is that to be expected for the mileage?
I imagine replacing the cylinder sleeves would somewhat resolve that if it were the problem. Right?

there are no cylinder sleeves in the stock engine

I have a suspicion that the CCV baffle inside the valve cover maybe be getting restrictive and the blow by finds its way out of the oil cap or gaskets

Dimitri16V said:

there are no cylinder sleeves in the stock engine

I have a suspicion that the CCV baffle inside the valve cover maybe be getting restrictive and the blow by finds its way out of the oil cap or gaskets

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We have to take the valve cover off to check the CV baffle?

it is built in

As long as milage and everything seems normal I wouldn't worry about it. Diesels leak here and there and oil gets here and there just the joys of owning a tdi!

You can try replacing the valve cover but I would have the compression checked first

If the rings leak , blow by would be too severe anyway

Run the engine with the oil filler cap off, if the blow by gases come up about 6" from the top of the oil filler cap hole you have way to much blow by, like said earlier this is caused by excessive crank case pressures, the textbook test is to check this pressure with a Manometer for the allowable Hg's....

volkswheels said:

Run the engine with the oil filler cap off, if the blow by gases come up about 6" from the top of the oil filler cap hole you have way to much blow by, like said earlier this is caused by excessive crank case pressures, the textbook test is to check this pressure with a Manometer for the allowable Hg's....

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this is largely false on our tdi's ... the vacuum pump exhaust creates an incredible amount of flow that can be mistaken for "blowby" ... true blowby is coupled with smoke, vacuum pump exhaust is clear air with oil droplets mixed in ... i've experienced an 203k mile ALH with the vacuum pump deleted and there is virtually zero air flow coming from the valve cover ... the same engine with the vac pump in place you could feel air flow eighteen inches from the cap hole ...cap off test is not valid in most cases on our tdi's, if it was then they would be "worn out" off the dealer's lot

Vacuum pump exhsust ??? Why would the vacuum pump exhsust be put into the crankcase? If that was the case the oil dipstick would also be forced out from the pressures.... Where on an ALH does the exhaust from the vacuum pump enter the engine?

High side of vacuum pump does go in the engine

volkswheels said:

Vacuum pump exhsust ??? Why would the vacuum pump exhaust be put into the crankcase? If that was the case the oil dipstick would also be forced out from the pressures.... Where on an ALH does the exhaust from the vacuum pump enter the engine?

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all i can say is next time you have an ALH vacuum pump off take a closer look

I've read through this thread a few times now and i'm not sure what to think. The one thing i can add to the OP is that the leak is very small if not accelerated over 3 or 3.5k. as soon as it goes over that level, i can expect to open the hood up and see the fresh oil on the valve cover.

So low RMPs (up to 3k) no leak, anything higher starts leaking ... This is based on visual inspections after having cleaned the valve cover with degreaser every time.

Is there a CCV valve that needs replaced? It does seem like it's built into the valve cover. I imagine just like anything else that might also wear out in time and need either replaced or cleaned. Right?

Any new thoughts on this would be appreciated.

It's a BEW with ~230k on it currently.

volkswheels said:

Vacuum pump exhsust ??? Why would the vacuum pump exhsust be put into the crankcase? If that was the case the oil dipstick would also be forced out from the pressures.... Where on an ALH does the exhaust from the vacuum pump enter the engine?

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What has to come in has to come out.

Jimbote is bang on.