Hi, I have recently purchased a '99 S40 T4.

First problem I had was in the cold weather when heater blower only blew cold air, this only happened twice on cold starts with minus temps outside, ran engine for short distance and engine overheat light came on. Checked coolant level and found to be way low, should've checked on purchase I know, topped it up and was running fine.

Second and major problem, drive home from work 3 weeks later and engine overheat light comes on, steam pouring out from bonnet. On checking coolant reservoir found milkshake mix in the tank!!!!

The question I have is will it be the head gasket thats gone?

I have drained the oil from the engine and it was clean, no obvious signs of mixing with coolant!!

 

More then likely, you have a crack in the radiator which is allowing the built in oil cooler's oil to leak into the coolant. Being the oil pressure is higher then the coolant pressure, this is why it gets into the coolant and not the other way around.

 

there is a test u could do to check if any combustion gas going in the coolant, if so u will @ least need to remove the head to diagnosis if there are any other damage or problems to the engine or head. the test is very simple, but require the equipment. is a tube w/special solution in it. place it on top of the coolant reservoir while running, if the solution turns it colour, then that mean the combustion gas is going in the cooling system