Hi Folks. Just a (hopefully) wee problem perhaps someone has the answer to. On raising the bonnet on my 96 GS300 this morning found the top hose flat and the expansion tank over full. On releasing the radiator cap the hose popped back so guess a vacuum must have been caused somewhere. As there was no obstruction to the pipe between the header tank and the radiator just cant work out what this could have been caused by. Any ideas and do you think it's ok to drive - am off on a fairly long trip tomorrow?

Has it had any radweld or somilar put in it? There are a couple of rubber seals on the radiator cap that all work together to allow the expanding water to get to the header tank and then back into the rad when it is cooling. If the route back through the rad cap is blocked then you may well get the same symptoms. Maybe just a new rad cap required?

On the mazda's, there is a two way valve in the cap that is nearest to the expansion tank..

It holds up to a certain pressure, but then allows coolant to flow into the expansion tank..
As the engine cools, the valve allows the coolant to flow back into the engine, if the valve is faulty, then there is a negative pressure and the hoses suck in..

Sounds like this is your problem, and a new cap should cure it..


John

i had the same thing with my old chevy camaro when the rad cap vent hole was blocked..

my 94 GS300 has a stuck thermostat, its wide open so its over cooling.. will try and get round to sorting that this weekend