BMW Repair: BMW 318 SE (Coolant/Radiator/Steam), radiator caps, combustion gases

Question
Hi

I have just bought a BMW 318 3 series SE, W Reg (2000), 1.9L.  I am at work and can't get access to the car at present to get the the last 7 digits of the VIN number - hope this doesn't cause a problem.

Shortly after buying the Coolant light came on so I bought some coolant, mixed it with water and poured it in.  The red marker popped up after only about 1.5L of liquid.  The next day the light came back on.  I checked for leakage and found nothing so I checked the coolant again.  The red marker had moved down so I added a further 1L of liquid.  The next morning the warning light was back on but I drove the car anyway as I needed to get to work.  After a 40 mile drive a lot of steam was coming from the bonnet.  I opened it and it looked to me as if it was the coolant that was burning and creating the steam.  There was a lot of liquid, condensation and steam all around the Coolant and radiator area.

Do you think I need a new radiator cap?  If so is this just as simple as buying a new cap £5 approx?

Any help would be great

Thank you

Pete  

Answer
Pete, have the system topped off and pressure tested for leaks. Radiator caps are a common leak point especially after the O-rings flatten out. It would be a good idea to replace the thermostat since the car has overheated. You can also have the cooling system checked for CO2 with a chemical "block" test. This will rule out combustion gases in the coolant, sign of a failed head gasket, cylinder head, or cylinder block.
-Evan