Could it just be a faulty thermostat? Easy to replace and if it has never been replaced would be one of the first things to try before spending big bucks.

Checked the car today. No loss of water overnight. Fan comes on when A/c button pressed. Fan comes on occasionally when A/c turned off and driving, so assume (risky) it's (hopefully) not anything major and may have been more related to hot day hot engine and reversing for a minute =no air flow. Into garage tomorrow for a refill and see if anything forthcoming.

You're right there David except that your radiator fan should have triggered and provided air flow. Best to check it.

Simon

Hi Simon

Just wondering if you could let me know how you test both fan speeds on a V8 using the demist test

Regards Dave

Highly unlikely though, really in the realms of "has been known". It's not a Rover engine, after all. Looking on the Two-Sixties shows only a handful of failures reported going back to 2006, and mostly explained by the obvious, like running dry of coolant, and two on supercharged engines.

David

If it is losing coolant one place you can check is the inlet manifold. The rubber gaskets between the top alloy part and the plastic can leak, it's quite subtle and can be hard to spot ;)
You need to check both sides.

The alloy corrodes and distorts the gaskets, in extreme cases it can crack the plastic ;)
Good old OAT strikes again.

I've got one sat in my kitchen at the moment have got it all cleaned up and ready to re-assemble.

If anybody wants a spare inlet manifold give me a shout.

Russ

Is there a way to test the fan other than to run the engine until it is up to temperature and see what happens? It comes on when I press the demise button, beyond that it's hard to tell because I'm behind the steering wheel driving the car.

Thanks for testing your fan's slow speed David.
The fast speed can be checked in the same way as for the other engines, by removing the trinary switch connector and joining the light green/red and black wires together provided that the V8's ECM allows it.

It would be more useful to activate the instrument pack diagnostics test no. 7.0 to monitor the engine's actual coolant temperature. The fan should start running at 99˚ and increase to fast speed if the coolant reaches 109˚C.

I suspect however that the unexpected overheating you experienced the other day was due to low coolant level of which you were unaware. Given that your fan is working on its first speed, I would continue to drive your car but check the coolant level on a cold engine every week. Ensure that the expansion tank is filled no higher than the MAX tab which should be visible by looking through the filler neck. If you can't see it your tank is overfilled and is liable to eject coolant which is what you don't want.

Please keep us up to date David.

Simon

Hi David

I would not advise joining any of the wires together as most of the systems on the v8 cars are totally different, As Big Russ has said look for leak of coolant on the inlet manifold and any other parts you can see if you cant find anything keep checking the coolant level and see if it is dropping, As for checking the fan operation is there anyone local to you that has a T4 if so they can easily check the fan operation for you

Regards
Dave

Fan definitely works on "demist". Absolutely no sign of life when up to temperature, engine running, parked. I would expect something, one of my long gone v6s did nothing but run on whether parked or driving - but that's another matter.