New oil leak head gasket?

[Gmg31]

I started my engine for the first time ever last week, it only ran (quite badly) for about 10 seconds  and I immediately noticed a new oil leak at the back.  I tried to start her again today and she was very reluctant to go but again I managed about 10 seconds and once again the obvious oil leak.  Upon close examination it is clearly running down the outside of chain cover at the back. There is also very obvious oil splatter on the bulk head.  To me this points to high pressure oil spurting out of the head gasket. Could there be any other cause?  If you've been following my story then you may remember that this is a brand new but unused federal Renault engine that was gifted to the previous owner by Colin Chapman but has sat unused for 36 years.

[jbcollier]

Retorque the head and reset the valves and try again.

[EuropaTC]

You can't argue with oil on the outside, that needs fixing. Whether it's related to the rough running or a separate issue I've no clues.  My usual first check is the plugs to see if they're running about right, although 10 seconds isn't going to be very accurate unless the mixture is wildly out.

Given oil seems to be escaping the next one would be for oil in the coolant followed by a compression test to see if the oil is forced out from cylinder pressure or just the oil pump alone.

Brian

[Gmg31]

Today I tried to identify where the oil was coming from and tried to slip my mobile phone in the gap to film it but I couldn't quite get the angle. What I could feel is definite puffs of air on my hand as I cranked the engine. It is certainly coming from the back of the head exactly in line with the head gasket.

[EuropaTC]

If you can feel air coming out that is a big leak. Given the engine has already been running and fuel mixture presumably forced across the sealing rings around the rear cylinder I would replace the headgasket.

You might just get away with re-torquing the head as John suggested, but I think I'd be more comfortable with replacing the gasket and checking the head for flatness. It might be that it's just been loosely assembled in the past and it all goes back together fine, but having been let down on the road with a blown headgasket, I'd sooner check while it's all in the garage.

Brian

[jbcollier]

If you decide to just replace the gasket, please read the relevant sections of the workshop manual.  It is very easy to go from a simple gasket change to a major overhaul if you do not remove the head correctly.  Under no circumstances can a liner lift up.  Do not turn the engine over with the head off unless the liners are secure.  If a liner does lift up -- EVEN A LITTLE BIT -- you must remove, reseal and reinstall that liner as per manual (might as well do all of them at that point).

Renault engines are tough reliable units BUT: they do not like air in the cooling system, and you must replace head gaskets by the book or you will be doing it again and maybe damaging the engine.

[Gmg31]

Thanks for that, I didn't know that so I appear to have been very lucky because the liners didn't move when I took the head off earlier tonight, phew....

So you can see from the pictures that the rubber seal around the timing chain had not been correctly fitted and is the obvious culprit. The air I could feel coming out was clearly from that area so the big question is.  Is there enough pressure within the timing case to create the puffs of air and tiny oil splatter on the bulk head? Or was pot number 4 blowing across into the timing cover and causing enough pressure to creat the puffs of air?

It's also obvious that this head has been smeared with red gasket sealant and this isn't a "new engine"  the Pistons and bores are however perfect so this may have been a test engine which has had the head removed for a quick inspection and then quickly bolted back together.

[jbcollier]

The crankcase builds some pressure as the engine is cranked: blow-by and piston movement.  Get a new head gasket set.

Be careful removing the head gasket.  "Peel" it off do not "lift" it off.

Do Not Turn the Engine.

Clean everything up and check your cylinder protrusion.

Might just be how the engine is lit but the oil looks filthy.

Now, stop and read the manual.  You absolutely have to have head alignment tools to refit the gasket.  Do not "eyeball" it.  That way lies disaster.

[BDA]

I assume you have a working PCV valve or otherwise vented crankcase. My thought, which is not from experience, is that you are probably leaking from a cylinder. I would check that the head and block surfaces are flat and reassemble. It's too bad you didn't do a compression test before taking the head off.

[EuropaTC]

Is there enough pressure within the timing case to create the puffs of air and tiny oil splatter on the bulk head? Or was pot number 4 blowing across into the timing cover and causing enough pressure to creat the puffs of air?

I agree with John on the crankcase pressure.  Even on a perfect engine there's going to be some pressure down there from the piston movement, it doesn't have to be blow by from worn piston rings.   As you say, it could be any of the cylinders leaking into the cam area but you'll see that from examination of the sealing ring around the individual pots when you remove the gasket completely.

Given the evidence you've found I'd be happy (well, sort of  ).    I'd check the existing gasket for even compression then rebuild. Any doubt from the other side of the gasket  and I'd check the head for flatness.

Brian

[pboedker]

I agree with John on the crankcase pressure.  Even on a perfect engine there's going to be some pressure down there from the piston movement, it doesn't have to be blow by from worn piston rings.

I am not sure I understand this, and just have to ask:
Shouldn't the piston movements in a 4 cylinder engine cancel out regarding the crankcase pressure? When two pistons go up, the two others go down, leaving only the blow by to add to the pressure build up.
Or am I missing out on something, here?

[jbcollier]

In theory, yes, you are correct.  Practice is another matter and depends on crankcase design and where the breather is located.

[Gmg31]

Thank you all for your advice.  One of the things I have discovered here is that at some point the head was removed and then a load do gasket sealant has been used to put it back together. If you remember this is meant to be a new engine but when I spoke to the heritage guy he said this is a federal engine and was probably a test engine.  So it seems to me it's been used for a very short period and the head has been removed for inspection.  It's probably a good job this happened because the sealant had blocked up several of the essential areas so this would have gone wrong sooner or later.  The head is currently being inspected and parts are on their way from Banks. So hopefully I can get this back together next week. 

[EuropaTC]

In a strange sort of way, that's all good news.

Now you know the engine itself is in good nick and have explanations for the problems you've had.  From the photos you posted it did look like someone had been liberal with the gasket goo, so daft though it sounds it's probably worked out for the best. It would have been tragic if some of that excess had blocked an oilway and wrecked an otherwise new engine. It's a real world example of why you shouldn't be too liberal adding extra sealant that we'll all learn from.

Looking forward to next week's update - "the engine's running !!!!"

Brian

[Gmg31]

Skimmed head and re seated  valves £118. New gaskets and ready to go.