Are you overfilling it? If you put too much in, when it heats up and expands, it'll be forced out somewhere. Only fill it to the max mark, no more. Otherwise it's got to be leaking somewhere, plain and simple. Wait 'til the engine's up to normal temperature then have a look over it to see if you can see anything. Watch the electric fan cutting in if you're leaning over the engine when it's hot!!! It'll come on suddenly. Also, don't touch any of the cables. It may be leaking from the rear of the engine and be impossible to see. The thermostat housing is down the bottom of the engine at the back...could be from there. Is there any sign of water on the dip stick when you check the oil? That suggests waters leaking in around the head gasket...nasty!! Best idea if you can't see a leak is to get a test done at a garage. Just tell them you want a colling system pressure test. They'll seal the top of the expansion chamber then pump it up over pressure to see if that shows up a leak. They may need to do a cylinder leakage test as well. That shows up any head gasket problems or any other naughties. It should cost too much. Best of luck!!
Denis Langley, February 2012
