Strange overheating problem

[andrew123]

Hi,
I'm hoping someone here can help me with my slightly odd overheating problem.

The car, 407 2L petrol overheated. The radiator wasn't hot so I went straight to the thermostat and, as I needed to get home, permanently opened it. Everything went well until I put a new thermostat in and, again, the thermostat failed open. The pipes to the blowers got hot but no heat in the rad.

I have no idea why the thermostat would fail to open.

Any ideas are much appreciated.

Thanks

Andy

[CitroJim]

On a 407 diesel I've seen a similar problem... Had us scratching our heads for a bit and found it was caused by the water pump. It had a plastic impeller and this had come adrift from the drive shaft so was not spinning and hence no circulation..

With the 'stat removed it's potentially possible there was enough natural thermo-syphon action going on to just about cool things...

The replacement was all metal and could not cause the same issue... Worth a check. Shame it's behind the cambelt.

[andrew123]

Thanks Jim,

Looks like I'll be booking it in then - it sounds like it's getting past my skill level.