2 days ago my Volvo S40 began overheating. Upon initial insepction, anti-freeze was pouring out of the reservoir. I was able to refill it with water and drive about 10 miles to my father's house. During this drive the car did not overheat. My father, who is a mechanic, looked at it, and his first thought was that the head gasket had blown because the oil and anitfreeze were mixed. However, after further inspection, we have come across some new findings. 1. Oil and coolant are in the coolant reservoir. 2. There is no antifreeze in the internal engine such as head or oil pan. 3. The transmission oil cooler is not leaking. 4. There is oil and antifreeze in radiator and engine block. 5. There are only transmission cooling lines to radiator, but no engine cooling lines to radiator. If there is no leak in the radiator or head, then where else could the leak be? and why has oil leaked into engine cooling system and not to internal parts such as the head or oil pan?

• 14 minutes ago
• - 4 days left to answer.

Additional Details

This is a 2000 Volvo s40
13 minutes ago
Yes, it has an upper and lower radiator hose that carries antifreeze from the engine block to the radiator, and is cooled by the cooling fan. There are are no engine oil lines attached to the radiator. there are only 2 lines to a transmission cooler which cool the transmission fluid. This is an individual cooler which is not integrated with the radiator. it is a self contained unit.
41 seconds ago

 

The turbo has both oil and coolant in the center section. Maybe they are mixing there.

 

If you're sure about the oil in the coolant being engine oil and not trans fluid, then the head gasket is the likely culprit. Engine oil pressure and combustion pressures are both higher than coolant pressure.
The oil cooler is on the right rear of the oil pan and is worth investigating also. Both, head gaskets and oil coolers, fail after so much time.
Ed

 

Sure sounds like a blown head gasket to me. Like Ed said, the high pressure in a cylinder or two is pushing oil and air/exhaust into the cooling system, which is pushing coolant out of the reservoir.

Time for a rebuild.

 

There is some cooler inside the tranny which when it leaks the tranny oil shows up in the reservoir.