Coolant in oil is easier to diagnose, but how about the other way around? Car is an early 2 valve Countach. Engine has maybe 1000 km since crank up rebuild, 4 years ago. It runs very well. I am finding some oil in the coolant reservoir, but no coolant in the sump. No condensation, no milky residue, no water vapour from the crankcase. Heads were checked for porosity and some pinholes were fixed (welded) before engine assembly. I recall the shop did some pressure testing then, but that was some years ago. What is a likely source of oil in the cooling system? Liner o-rings? Bad head gasket? Some porosity in a head we did not find? Liner deck heights all checked out ok when we built it. As oil is getting into coolant, it would seem that oil is being forced through a hole or crack from a passageway where oil is under pressure into a coolant passage. Next stop may be to pull the engine, pull the heads and get them pressure tested. Any ideas where else to look? I thought about a water pump seal, but two seals would have to fail and there is no dripping from the bleed hole at the underside of the pump.
I have no idea how an early Countach motor is designed, so let's get that out of the way first... Generally oil in the coolant stems from a failure in the head gasket where the oil passes from the block up to the heads (since coolant passageways are also typically nearby). When you shut your engine off, the cooling system contracting can also produce a vacuum which can suck oil in. Does your motor employ any sort of dry sump or oil cooler that might also utilize coolant? Perhaps there is a failure in some heat exchanger or something. Have you considered using one of those chemical test kits that detects exhaust gases in the coolant? I think that would be a good next step and could perhaps help highlight whether a head gasket issue is lurking. Again, no first hand experience with Lamborghini motors. Ray
Countach engine architecture dates to 1963, so it is pretty basic. The quality of casting of blocks and heads, even in the early 80s when this car was made is pretty atrocious. There is no dry sump, or water/oil cooler; the places where oil and coolant are near to each other are all inside the engine. A good idea to check for exhaust gasses in the coolant - I can do that. Finally, a good observation on the head gasket - there are places where the distances between the oil and coolant passages are not large. Many thanks.
I know nothing of Countach motors but in many italian motors the water pump is a path for oil/water interchange.
In the 400, the oil filter risers are notoriois for enabling such "exchange". Maybe you should use a pressure cap that allows the air to "get in" while the system cools down. This would adress Ray's concern (under pressure when engine is cooling down). Stant 10231, with a "dangling" valve, or Calorstat rc0153 if you are based in Europe.
Apparently the water pump seal drain hole is too small and can block with corrosion. The coolant is then forced into the oil over time; in extreme cases the coolant can wash out the bearings and wreck the engine. There is no coolant in my oil as far as I can tell; there is only a layer of oil at the top of my coolant reservoir. The water pumps seems ok in any event, the bleed hole seems ok, no dribbles. I cannot entirely rule out the water pump (which is an unbelievable pain to change, let me tell you!) but it makes it slightly less likely. Some examples apparently had problems with too high oil pressure when cold which could cause issues. I never rev it much until the oil temp gauge moves, and never saw any excessive readings. The radiator cap on it is rated for 1.1 bar; were excessive pressure to be there I could see an issue. I will probably replace it anyways. If one or more of the liner o rings were bad, my guess is that the coolant would make it into the sump. All this did get pressure tested when the engine was built. It did sit for a few years after assembly, probably not ideal.
Too much pressure on the coolant should result in coolant in the oil, not the other way. The radiator cap with dangling valve allows to avoid negative pressure in the system: once the pressure reaches zero the valve "floats"/"dangle" which lets air into the system. Most modern cap are "sealed", as the old-school caps let fresh air and oxygen in the system which is not good for corrosion (at least on cars that do not see frequent coolant changes). However these old type of caps prevent the cooling system from sucking oil when the system cools down. (I frequently go the Alps, so I prefer to let the system equalize its pressure.) Please note that I used to have some inorganic coolant that would leave some oily residue under the radiator cap (IGOL coolant). The residue was some kind of petrol jelly. This was "minimal", like a 2mm layer on the radiator cap. I suspect this was related to the additives. Not experiencing this any-more (I now use SiOAT).
A while back I encountered excessive amount of coolant-in-oil in a early seventies V12 Ferrari engine and after various preliminary diagnostic tests along with review of previously performed service records (of someone else's work) showing a "water pump rebuild" done several years ago (but hardly any miles driven since) lead me to take a closer look at the water pump, only to discover its seals had been incorrectly assembled (or should I say "butchered" in to place?) and were blocking the weep hole in the housing. There were other signs of "butchering" in that water pump assembly, but these were likely not directly contributing to the aforementioned problem. I am monitoring the issue with periodical oil testing and so far, things look promising.
I spent a few hours on this yesterday. What is remarkable is actually how little oil is needed to produce that film at the top of the reservoir tank. Maybe a few cc at most. I drained the reservoir, cleaned it, refilled it and ran the car for an hour. I will go back today and check the amount of oil in the system. Perhaps the cooling system was not clean when we assembled the car? I know they use something on the o rings when they insert the liners into the block. Is it possible it could be something thar simple? I rechecked, the water pump bleed hole is clear and clean. Joy.
