Hi. Have recently got myself a 1998 mondeo 2.0 6v zetec. I noticed it had a slow water leak from the thermostate housing. It also required a new rad, as the old one had split at the top. I replaced the rad and will be sorting out the other leak very shortly. The problem is that after replacing the rad, the car over-heated very quickly, far quicker than with the damaged rad. I have very limited knowlege of fixing cars but i would hazzard a guess that this is due to that fact that now the radiator doesn't leak, there's nowhere for the pressure to release? So my question really is: Could it be the thermostat housing (or a part inside it) that is causing the overheating and maybe stopping the circulation? I also noticed that when i loosened the lid of the filler cap, it bubbled away frantically like a witches cauldron which led me to thinking that, for that much air to bubble, the water isn't circulating properly (if at all). I do realise that this could be the water pump but don't want to jump to too many conclusions as my brain is now hurting Any advice welcomed.

I'm no expert but if it over heated without loosing water then i would look at the thrmostat first. i think if water pump gone then they leak because its normaly the bearings that go in them. i've never had a car air lock so not sure if they do.