1995 Windstar Air Entering Coolant System

[j_brand]

I have a 3.8L 1995 Windstar with 180k KM that has recently begun overheating. Air is entering coolant loop and forcing coolant into the radiator reservoir. On a 45 minute drive in 15'c (57'f) weather it will almost fill the reservoir and when it cools I have about 1/2 a reservoir of coolant ( over and above the minimum level that I fill it to) that does not get sucked back into the radiator as air has replaced it. Almost the same amount of coolant will be missing from the top of the radiator.

When the coolant system is full it functions fine, temp is maintained on the "A" in NORMAL and both heaters work fine. I can see the slight fluctuations in temp when the thermostat opens and I have felt the upper radiator hose heat up on opening. When too much air is in the system the temp fluctuates from N to A in several seconds, both up and down.

I can find no source of coolant leaks on the engine or vehicle and I see no oil in the light green milky colored coolant.

The oil does not appear sludgy.

Compression testing shows 155 to 165 PSI on all 6 cylinders.
Spark plugs all seem to look exactly the same.
While the engine is warming up it puts out a lot of steam and drips water out of the exhaust pipe every 3-4 seconds. Once warm the exhaust is dry.
Engine power seems a bit low and hesitant, but it's an old vehicle.

Fluid can move freely into and out of the reservoir and I have replaced the radiator cap already. I have not done a radiator leak test yet.

About 6 months ago I replaced my oil pan seal and it seemed to me there were drips of green antifreeze coming down from one of the middle cylinders (2 or 4). A friend suggested using radiator sealant (can't recall the brand I used but it was a small white bottle with an oily liquid and what looked like small ball bearings in it) and I have not noticed any sludge.

Question: Am I dealing with a Head gasket issue or is there another possible cause for air being forced into the cooling system?

Thanks

[phantom_smack]

I would have to agree with the head gasket issue

[BryanF]

could very well be a small head gasket leak that only presents iteself when the engine is cold. that's how mine started, and eventually worsened until it was buring coolant all the time. or it could be a leak in the lower intake manifold gaskets, where coolant leaks into the intake ports and ends up in the cylinder. but the fact that air is being pushed into the system somehow makes it more likely to be a head gasket, because if you are leaking coolant through the intake, coolant would be getting sucked out of the system (rather than air getting pushed in)

if you know there's coolant leaking down a cylinder and into the oil pan, that is definitely cause for alarm. consider getting a professional's input, because something definitely sounds wrong with your van.