Head Gasket Oil Weep

[david.g.chapman]

Well, we have all had these before!

I have had one at the back of the head on the right hand corner, as viewed from the front of the car, for some time. Not a problem, just a bit messy after 2000 miles, then its a quick wash with paraffin.

In one of my idle bodgy moments, I thought of cleaning the area up with meths and slapping some RTV over the head joint, 2mm thick, to about 10mm above and below the joint and 30mm along either side of the corner. I then did 30 miles of mixed motoring, and looked again, fully expecting the oil to have forced its way out again, backed up with 35 psi of pressure. No sign of a leak!

Then I thought about it, and there is only a head bolt hole near that corner, then a waterway opening on the back side.

Where was the oil coming from, and what pressure would be behind it? Spooky

Note - oil is not seeping down the head from the cam cover joint and the D inserts.

Dave Chapman.

[leifanten]

Dave,
with the caveat of sometimes getting confused with right and left on engines, it sounds like you are talking about the rear end of the exhaust side of the engine. (right side looking at the engine from front) ? I thought the oil pressure side of the engine was on the inlet side & front end where the oil gallery and the feed to the cam shafts are. I must say I struggle to see where you could have an oil leak at the rear&exhaust side that was backed by any pressure from the oil pump.

Is the compression on #4 cylinder ok? Even with a leak down? That is the only source of pressure that could blow oil out in the mating surface between head and block in that area, and even then only through a roundabout route from the opposite side of the engine?? Otherwise this corner is occupied by a cooling water duct.

[david.g.chapman]

Yes, it's the back of the exhaust side.

I had a leak before the head gasket was last changed, and compression on no. 4 is OK at 160psi with my low compression head (same as the other 3, more or less). There is no cross-contamination of coolant and oil that I can see.

Is is possible that oil is getting into the bolt hole in that corner from the camshaft space? The oil would have to pass the top of the torqued head bolt and its washer. It is then only 5mm to the outside world across the head joint. I think the bolt holes in the block are blind.

So that could be why the RTV is working so far - there is no back pressure apart from the column of oil surrounding the head bolt.

If the RTV fails in future (quite possible) then I could try removing that head bolt and sealing the top - would the head distort with one bolt temporarily missing?

Dave Chapman.

[leifanten]

David,
I dont think there are any oil return paths on that side of the engine. Here is a theory for you: If the bolt hole was not cleaned up before putting the head back on, then the residual oil from the bolt hole would be forced out when torqued up and make its way out. That would certainly explain that a bit of RTV fixed the problem. I always use a hole bunch of Q-tips (cotton pins) to completely dry out the bolt holes to avoid an issue with oil being forced out of the hole when torqued.

[leifanten]

To answer your other question on distorting head from removing one bolt. That is one of those maybe, maybe not issues. I would be reluctant removing one bolt and retorquing it, simply because it does not feel good. I have done it once (to re-position one of the D-washers during assembly - it had rotated to where it touched the cam thrust bearing and had to be re-positioned) and it worked fine (so far) but, I was really not feeling all pepped up about it when I was doing it.

I find it highly unlikely that oil creeps down around the bolt, it forms a metal to metal seal with the aluminium at high load.

[david.g.chapman]

Very strange.

When the oil was leaking it worked its way down the engine to the clutch slave cylinder, covering a fair amount of area. It was as if it was being fed from the rest of the oil in the engine. The fact that it is not leaking now with the RTV just over a section of head joint means the leak was coming from that area as well

The only thing left is a route though a internal void/crack/flaw in the head (or block) from the oil galleries to the bolt hole. There is no external sign of anything amiss, and as it has been leaking there (on and off) over 9 years and 40000 miles I will motor on with a smile on my face.

When I pull the head next I will have a good look there.

Thanks,

Dave Chapman.

[nico506]

Hi All,
I have just finally got my engine started and running after a long resto programme, and have notice head gasket ol weep at the rea of the block on the exhaust side. At the moment oil pressure is holding a 40 psi , compression 170 all cylinders, runs fine and as far as can tell no water in oil or loss of coolant, oil coating is like a black mist on side of block. Checked head bolt torques- all ok.

Should I leave this and run the car for a while as have hd comments 'like the oil is under alot of pressure and is bound to leak'-albeit weep.

Is this normal and should I lift the head and put new gasket on for peace of mind.

I know some of you hve lived with this issue for a while with no adverse problems -but thought of oil coating the exhaust pipes - worries me a little!- petroleum based product + heat= fire

Any one willing to offer suggestions as to how best to approach this - as like evryone else- had setbacks and keen to resolve this before it gets worse if that's the case.

BTW- head has been skimmed- could this be the problem?
Thanks in advance for comments and tips

Nico

[david.g.chapman]

Hi Nico,

Check that it is not the cam cover joint and D inserts that are leaking. If the back and side of the head is dry then it's not that. You will have to feel for oil at the back to be sure.

There is also a brass gallery plug just above No 4 manifold in that area (not sure if it oil or coolant). Look for leakage there as well.

Otherwise look for oil tracking across the block from somewhere else (blown back by the airstream)?

De-greasing the entire area with paraffin/turps substitute and test running the engine will help you see where it is coming from.

Dave.

[kstrutt11]

one of the tricks i've seen used to find oil leaks on test engines is to clean it up then spray the offending area with the white developer used with crack detection fluid, the location of the leak is then easily identified.