Bad oil leak ?

[V40addict]

Car is a 01 V40 130 000 miles, petrol, auto gearbox, there is oil seeping from the cylinder head, oil makes its way to the accessory belt area (one pulley has a bit of oil on it). The rear of the timing belt plastic cover also has oil on it. My guess is it comes from the head (gasket ?) or the sparkplugs, but I am no mechanic and didn't have torx wrenches on hand to remove the plastic covering the spark plugs.

How bad is this if I wanted to fix it ? There is no other sign of head gasket failure. I didn't notice much oil under the car.

[canis]

Might be the oil seal. Each camshaft has an oil seal at either end. I'll keep it simple.

The top of the engine, through which the spark plugs go, is the "rocker cover". It's called this because underneath it are traditionally "cam followers", which rock, each actuating a "push rod", which forces open a "valve" in the cylinder. The days of cam follwers are gone, replaced by newer technology ("hydraulic lifters") but the rocker cover name has remained.

If you look closely at your engine, you'll notice there is a very fine seam between the rocker cover and the cylinder head, with black circular plastic oil seals halfway between the two. Behind the seals are the ends of the camshafts, which sit in high pressure oil, so the seals are important because the camshafts don't use any bearings, they literally just rest between the rocker cover and the cylinder head with high pressure oil squished between.

They all leak eventually.

I would change the oil seal before before blaming the head gasket for the simple reason that you can change these without splitting major engine components apart. Especially since you are not noticing any other symptom for head gasket failure. Changing a head gasket is very invasive and rather complicated.

Changing an oil seal is much simpler. Basically the procedure is this: Remove aux belt, remove timing belt, remove the pulley, pluck out the oil seal, knock the new one in, then put it all back together again.

So that's where I'd start if it was me.

[V40addict]

Thank you. It would make sense, if these seals are gone, oil under pressure is sprayed all over I suppose, therefore even the top of the timing belt cover is soaked in oil.

The procedure you describe involves a lot of work though, like changing the belts, and the timing belt has been changed 2 years ago so not coming due.
If the car isn't driven much , can you get away with not doing the repair ? Or is the oil really bad for the belts ?

[canis]

Difficult to be sure. You'd need to ascertain exactly where it's coming from to be certain.

[V40addict]

I read it could also come from a VVT pulley seal, would make sense since there is oil on its cover but on the other hand there is even more oil seeping from around the thermostat and down the accessory belt (exactly like I had coolant leaking on another car) so I don't think this would be the VVT pulley seal.
Either way, it looks like a costly repair. I read the belts can slip because of the oil. Does it do the same damage as a belt failure ?

I will try to look closer this week.

[canis]

Yes, that's exactly the seal I was describing. I said camshafts, but that's because the VVT pulley is attached to the camshaft, and where the shaft goes through the side (actually the front, but let's not be pedantic here, transverse engines like these are mounted sideways in the car just to confuse things) of the engine there is a seal.

I'm intrigued by the oil appearing on the thermostat housing though. Directly above that, on the very top, there is the VVT solenoid which controls oil flow to the VVT itself. So that's a potential source and much easier than messing around with belts.

Or even the rocker cover itself. It has a liquid gasket rather than a traditional cardboard one. Has the engine ever overheated?