I had my '87 944 N/A at the track for a DE day. Son driving it, actually. He brought it off the track and parked it and it proceeded to expel a good 1/2 gallon of coolant. In the puddle, it showed foamy oil on top.

Turns out the temp switch is the radiator had failed. I jumpered the relay connections in the fuse box to bring both fans on, topped up the coolant and sent him out again.

The car made a couple of more runs and barfed coolant after most even with both fans running and turning the engine off. I did bleed the radiator correctly with nose up and venting through the vent bolt.

The coolant that came out always seemed to have some oil in it. Once the car cooled there'd be some drips floating in the reservoir.

I was out fixing it today. Drained out the coolant and it looked oily. I replaced the thermostat (why not) and while it was out overnight that outlet on the pump collected some fresh oil. Not just oily coolant but, it seemed, some mostly-oil puddling there. Maybe a couple of tablespoons but that all unwelcome.

I've looked the engine over and don't see an oil cooler on it. I was thinking "cracked head" but I don't see how that'd drip into the water pump. The car drives fine on the street with the fans jumped ON.

Any thoughts or ideas from the collected wisdom?

 

My first thought is that your oil cooler seals are failing requiring new seals and a system flush, but I would do a leakdown check first to confirm everything is ok up top.

 

The oil cooler is what the oil filter screws onto. It's a boxy looking thing on the side of the engine.

 

Thanks. I've swapped engines and didn't figure that out along the way.

 

On an 87 NA, you won't be able to see the oil cooler (oil/water radiator) externally, it's inside a casting.

Oil and water interfaces are isolated by multiple gaskets/orings.

With one, or the possibility of multiple gaskets/orings leaking, keep this in mind when making a diagnosis....., when the engine is running, oil pressure will overcome coolant pressure (even 20 psi OP at idle overcomes 15-18 psi CP limited by cap release pressure), thus, oil would leak into coolant. When engine is shut off, OP will be -0- but coolant pressure can remain at <18psi until engine cools down so coolant would enter oiling system.

With oil pressure at -0- on a cooled engine and most/all the oil back resting in the sump, the only way you should be able to get oil into the thermostat opening of the water pump (which is higher than oil in sump) would be from gravitational feed from above the water pump. The only parts of the engine that would have a quantity of multiple teaspoons of oil stored would be the cylinder head/cam housing, the oil-coolant radiator (internal cooler) and the oil filter.

Both of these would have enough weight to leak into a drained and unpressured cooling system...., upper engine oil could theoretically leak into coolant passages at the head gasket where cylinder head/cam oil feed passes between the block and head but the pressure reducing valve would have to be failed open to allow drain back.
The weighted oil in a full oil filter or internal cooler could slowly leak into the cooling system as long as the system was opened without pressure or weight of water counteracting.

Seems that if your cooling system checked good, in that the hoses would remain hard with pressure after the engine was shut off, you'd have coolant in oil too.

If there's a leak between oil to water, there is nowhere that it would not be bi-directional that I can think of if coolant pressure was present like a healthy system when the oil pressure was -0- with the engine killed.

Fill cooling system and bleed (with just water for test).

Drain engine oil.

Apply radiator pressure tester and pump to 15 psi.

Place clean pan under open oil drain port and watch for water dripping into pan.

T

 

Thanks for the ideas. Doing a bit more research I think the oil cooler is very likely. Not sure if it'd just drip out of there into the water pump but the two bit are right adjacent.

The water system goes to 15psi and the oil goes to 5 bar which is 75psi. Still no obvious contamination of the oil. Perhaps lucky. I'll likely be tossing the 2 gallons of Amsoil racing oil that's in there.

 

Correct. But when engine is shut off, oil pressure goes to zero but coolant system pressure is still present, evident by the firmness of your hoses.

The 8V NAs have the internal oil-water radiator (cooler), the turbo cars do not but they exhibit the same type of failure so it's not necessarily the internal cooler itself but the o rings at the cooler connecting piece and/or housing gasket.

You can pressure test the cooler once you have it out, they were known to fail.

There's a factory bulletin on how to properly shim the cooler during service as it's kind of wobbly fitting in the housing.

If you find it's leaking, a good used one should be easy to find (I have several) because race dedicated cars usually have this piece deleted in exchange for the type without the oil-water radiator in favor of an external air-oil cooler like the 944T has.

You could probably convert to external type for the price of a new factory internal cooler. They used to be pretty pricey.

T

 

As a related side note, I've often wondered whether an internal cooler is better than an external one. Also fitting an external 951/S2/968 cooler to cool efficiently on a 944 front valance is difficult without cutting holes.

I'm guessing but I would think an internal cooler works better on a road car as it's constantly getting cooled by a flow of coolant even with the car stationary, whereas an external cooler only gets airflow while the car is moving. Likewise, I can see why an external cooler is fitted to track cars as there is no constant stop-go traffic and plenty of airflow.

 

Good points.

The cars with external would have sat at red lights and stop and go too though.

Maybe on the turbo,and other higher hp cars (the radiators are taller), cooling the oil overtaxed the cooling system....?

The important feature for the street car is that the coolant is held in the block by thermostat to warm quicker and in turn warms the oil on sub freezing days.

The oil thermostat in the external types address this by only allowing oil through the cooler once a preset temp is reached but there's no additional warm up feature like the NAs via interface with warming coolant.

T