Oil and water are mixing

So I finished installing the Petronix distributor and coil. On a trial run the car does seem to be more peppy. I’m smiling, until…

I get back to the garage and see a slight stream of brownish fluid draining on to the garage floor about where the expansion tank overflow hose is. I don’t recognize the fluid; not brake fluid, not antifreeze, not oil, not battery acid. I wet a finger and sniff it. Smells like antifreeze but why is it so oily? I pull the dipstick; where did that quart of oil go? It was there the last time I checked the dipstick.

Apparently the car has decided it wants to mix oil with the antifreeze but not the other way around. The oil on the dipstick shows no sign of water being mixed with it. looks OK, no sign oil contamination. The overflow tank and radiator neck, on the other hand, show clear signs of oil being added to the coolant.

So some boundary between the cooling system and lubricating system has been breached.

What are the likely places to check? Where do I start. “Why me?” as Nancy Kerrigan once cried out (gotta keep one’s sense of humor in situations).

As always, any and all help greatly appreciated.

Here I am thinking out loud where is the oil pressure higher than the water
pressure in the water system and the possibility of a mix

Only two possible things, John. Either the head gasket or a crack somewhere. As the Queen of Hearts said, off with her head!

Wish I could suggest something easier.

Sorry for the bad news!! The only time I ever saw this was a blown head gasket… Austin Healey.

Oil pressure is nearly always higher than the water pressure which is controlled by the radiator cap in the area of 10-13lbs.

Who’s George? :slight_smile:

The consensus seems to be head gasket. I was considering pulling the head anyway and taking it to Dick at Coventry West for a rebuild. Looks like that decision is about made.

Sorry John, :blush: brain fart, lost track of the OP when answering…

No foul Jack, uh, Paul. :sunglasses: :grinning:

thinking out loud…but if engine is off and the engine/water is hot wouldnt the residual water pressure then be high enough to push back the other way causing water in the oil too?

just curious.

Bob F

Certain seems logical. I’m curious too. Maybe it does, just not enough to be noticed quickly considering the length of time the water pressure is higher than oil pressure. And that the motor isn’t running so not mixing the water and oil. Next engine heat cycle, water evaporates leaving a few drops of anti freeze. That’s a bad thing but might take a long time to build up enough to be noticed and/or do damage.

_I’ve got no solution_but I do note firstly that there is no pressurized oil near a water gallery, nor in the head gasket area, and secondly, after you shut the engine off and oil pressure goes back to zero there is still pressure in the cooling system that should now push coolant into the oil gallery if there was a crack etc there. One area that oil and coolant come close together is block coolant outlet into the water pump. The coolant has to pass through the timing chain cover, and if that area is not adequately sealed you can get water going into the oil, but the opposite isn’t generally true as there is no pressure in the timing chain cover.

When you first start an engine that has been rebuilt the engine “takes up” a quart of oil into various areas - like the head, oil filter and appears to be a quart down when you shut it off.

Have you tried pressure testing the cooling system? Did you put Bars Leaks or a similar fluid in? It’s got a brown yukky appearance.

Thanks Terry.

Knowing that is a fairly common problem I considered and then rejected it for the reason you cite.

The engine is not recently rebuilt nor was the oil recently changed. The fluid level in the expansion tank, on the other hand did increase to overflowing.

I did put in Bar’s leak, but this isn’t it. It is most certainly oil in the coolant.

I’m going to be doing that. I have a device I made a long time ago consisting of a pressure gauge, connected with valves and fittings and tubing. It goes in line between overflow tank and the radiator filer neck and can be pressurized with an air compressor. Pressurize the system, close the inlet valve and watch the gauge to see if it drops. Works just like the system they use to check the integrity of home plumbing systems during construction.

For oil to get into the coolant, but not the other way around, strongly suggests the fault is in a location where the oil is pressurized. There is very little pressurized oil in the head - it enters through the banjo fittings at the back, then goes through the cams. I think leaks from any of those places is highly unlikely, with the most likely being a crack between the water jacket and the (very short) passages between the banjos and the rear cam bearings. There is NO pressurized oil passing through the head gasket, so I see almost no chance this is a simple head gasket failure. The most likely source seems to me to be a crack somewhere in the block, where the oil galleys and cooling jacket are separated by rather thin cast iron walls.

Ray L.

To get oil in the coolant, you need a place where the pressure of the oil is greater than the water pressure. If you had a 2+2, the first question would be if it was an automatic as the cooler could have sprung a leak. The only area on the head gasket that would be a possibility is at the rear where the oil drains back to the sump. However, this is under no pressure so to migrate to the coolant and not the other way around is rare indeed. The water pump as mentioned in another post is common but usually getting coolant into the oil. Even cracks in the head result in water in the oil. Best to try to determine the cause before any major surgery as it will be hard to duplicate without it together. I would recommend retorqing the head for a start. Head gasket most likely as the pressure from the combustion will push into the cooling system. This usually results in coolant in the oil though. After retorquing, put a pressure gauge on the coolant system and pressurize the system to 10 PSI. Now start the engine and while watching the gauge, rev the engine hard and see if the gauge goes up . The gauge will rise slowly through normal warming up of the coolant. What you are watching for is the coolant being pressurized from combustion pressure leaking from the head gasket.

John, Sorry to hear this.Don’t forget that the timing chain cover is a place where oil and coolant chanels are close!

Oh, me. Tanya Harding ??? Nancy is living her life just fine.,
Tonya, not so much.

Barr’s leak, ugh. None great but there are better sealants. My opinion.

Yeah, if it was an auto car, that is where I would look. It isn’t, so, elsewhere…

As a past mentor often stated, "think it out’. Here, where do the coolant and oil systems get cozy?


I hope we resolve this because even tho its John with the problem I’m very curious to know what the mechanism is to get that oil into the water. And once we figure it out may we never see it again :slight_smile:

Sounds like a plan. Just so I’m sure, what is the procedure for retorqing the head?

Do I loosen all 14 acorn nuts and then retorque as per the pattern in the service manual?


Do I loosen and retorque each one individually.

Well, I for one am hoping to never see it again. :frowning:

John please remember there are 6 more nuts that need to be addressed. And just a question is your block original or from a later car?

Original block George.

To reask the question I posed to Dick. Do I loosen them all and then torque them down as per the diagram in the service manual?