Mystery oil leak

[Cubieman]

What could cause oil to build up on the edges of the HG besides the HG itself being bad?

I am getting a bit of what I believe to be oil building up under the vanos in the highlighted area. I have not found any significant amounts of oil/drops, the highlighted area is simply greasy/dirty.

I have checked the following items and do NOT believe the cause to be:

- Vanos gasket/o-ring plate
- Vanos line
- Timing chain tensioner
- VCG

When driving the vehicle with the windows down I have been smelling burning oil that I believe to be seeping from this area, the harder I drive the worse the smell when comming to a stop.

Could a timing cover leak cause oil to form on top of the HG like I am seeing? I will have to pull the front clip/radiator and clean this area up and see where the oil forms.

[sapote]

Have you checked the upper right chain guide mounting bolt and its crushed washer? also, the vanos metal gasket still a prime suspect to me. If the timing cover is leaky then I would expect to see more oil at its bottom than at the top.

To really avoid any leak, I would add a little sealant on all gaskets and crushed washers before installation, except the head gasket as it has tremendous clamping force.

[Cubieman]

Have you checked the upper right chain guide mounting bolt and its crushed washer? also, the vanos metal gasket still a prime suspect to me. If the timing cover is leaky then I would expect to see more oil at its bottom than at the top.

I have not checked that bolt nor know it's specific location but I'll find it, not all that familiar with this area of the engine as I haven't done removed anything except the vanos.
Its quite hard to get a good look at this area without removing the vanos/front clip.


I also will reluctantly do a compression test, just afraid what I may find out per usual.

I wiped the oil and dirt off of the exposed parts of the HG both right/left sides, I'll see how long it takes to come back.

When under the vehicle I can see and feel oil under the head/HG that I believe to be running down the engine from the front.
Never drops of oil, just a thin film.

[FBloggs]

Vanos sealing or cam cover, I would think.
The scent of oil while in motion suggests oil on the headers.

Is a 3rd party oil/vapor separator installed?
I got the oil/fuel scent in the cabin after installing one of these.

[heinzboehmer]

Yeah check the bolt sapote mentioned. It goes through the head into the timing chain guide on the driver's side and is obscured by the thermostat housing. If you shine a light in the space between the head and housing you can just barely see it.

Compression being okay or not would not tell you if the head gasket is bad at the front of the engine. Head gasket holds compression between the block and engine, but the block ends before the head does. So the role of the head gasket in front of cylinder 1 is just to seal oil in. Point is, don't rely on compression test results to tell you if the head gasket is leaking between the head and timing cover.

[Cubieman]

Vanos sealing or cam cover, I would think.
The scent of oil while in motion suggests oil on the headers.

Is a 3rd party oil/vapor separator installed?
I got the oil/fuel scent in the cabin after installing one of these.

No catch can, and oil may very well be making it to some of the front most header flanges. I did notice this smell increased after installing a CSL airbox fwiw.

I'll pull stuff apart soon and report back. I have used a borescope to inspect the underside of vanos and that metal gasket appears very clean. But this oil leak is so slow its entirely possible it comming from the vanos, dripping down, then the oil the leaked from vanos has as burned away once I am looking around for it.

I am interested in the bolt sapote mentioned and heninz noted location as there is a bunch of wet dirty grime right around where that bolt is located, or so it would seem.

Also, if that bolt was leaking it would make sense to have oil in the areas that I currently do, the slant of the engine would move oil to the pass. side and wind would allow oil to roll back along the underside of the head back to about cyl. #4 as it does.

Edit: Is this the bolt in question?

[heinzboehmer]

Yeah that's it. No need to take anything apart to check if it's leaking. Just shine a bright light between the head and thermostat housing and check for oil/grime beneath the bolt.

If you see some, try cleaning up the area as best as possible. It's hard, but can be done by spraying brake cleaner and using a rag on a screwdriver. Don't get brake cleaner on your belts. Then drive the car around for a week or so and recheck. This is necessary to rule out the possibility of oil being there from an old valve cover leak or from spills when changing the oil filter.

[sapote]

Have you checked the upper right chain guide mounting bolt and its crushed washer? .

These are #7 and 8. Upper right when viewed from driver seat as standard in all books. I didn't mention the #10 and 11 parts because most people had changed the upper right chain guide which worn thin and broke after 70K miles.
Yes, check #7, 8, and 10, 11.

[Cubieman]

These are #7 and 8. Upper right when viewed from driver seat as standard in all books. I didn't mention the #10 and 11 parts because most people had changed the upper right chain guide which worn thin and broke after 70K miles.
Yes, check #7, 8, and 10, 11.

I replaced #8 when I changed out my upper RH chain guide which was indeed broken at 67k miles.

This area is quite hard to inspect with everything in place unfortunately, even with a borescope albeit mine is cheap and low resolution.

[heinzboehmer]

No need for a borescope, just shine a light from a bit further up and you should be able to see. Have to play around with angles but it'll work. This is a vid I managed to get of mine when the bolt broke:

https://youtube.com/shorts/u9VNHvYrD4Y

You'll be able to see all the way down to the block without a screwdriver in the way


Edit: found a couple pics that show the bolt and the angle necessary to look at it with everything still on:

[Tbonem3]

How much needs to be removed to R&R that bolt (well, crush washer I assume)?

[heinzboehmer]

How much needs to be removed to R&R that bolt (well, crush washer I assume)?

Just the thermostat housing.

Which is honestly a pain because you get to deal with coolant spilling everywhere. And you probably want to take the belts off so they don't get soaked in coolant. And that means taking off the mechanical fan if you have it installed, etc. etc.

[Tbonem3]

Thanks

[Cubieman]

My bolt definitely wasn't loose like your Heinz, not to say it's not leaking. There was most definitely grime under the bolt head and ~3" rearward of the bolt as well.

Something upfront is leaking and I assume the air is blowing the leak (presumably oil) around the edges of the engine where the heads meets the block.

I was able to position a small mirror and did not see oil comming from either of the top chain guide bolts, but this leak is quite slow.

Last oil interval (2,800miles/12month) my on OBC indicated that I had lost .4l over that period of time, however my dipstick did not show any oil loss.

I have a tendency to discount the digital oil readings, specially the average. Right now my average after 300miles shows .1 on the display but the real-time digital display shows .6 and the dipstick is almost 3/4th's up between the two marks.

I'll let it go now that I cleaned the dirty areas up and check it out in a while. It sure does smell like hot oil when I am driving, almost stings my eyes sometimes though like an uncatted vehicle which is odd.