The thermostat housing is, facing the engine from the front, at the front of the engine, on the right, down at the bottom, near the turbo. On mine, a '99 E300td estate, I had to buy a new housing as well. Incredibly in my area, the third largest in the UK, it had to be ordered in. Apparently it is because it is so old........................And it has a 30 year Mobilo warranty!