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[05omegav6]

The cooling system on the Omega is designed to work as a complete system... yours has/had at least two failed elements:

1. Fans not working correctly.
2. Stuck thermostat.

So it would have been slow to warm up, but once upto temp, it would quickly cook.This left only natural, unforced airflow to cool the radiator. Had the fans worked correctly, it would have run cold as you expected

[Andy A]

The cooling system on the Omega is designed to work as a complete system... yours has/had at least two failed elements:

1. Fans not working correctly.
2. Stuck thermostat.

So it would have been slow to warm up, but once upto temp, it would quickly cook.This left only natural, unforced airflow to cool the radiator. Had the fans worked correctly, it would have run cold as you expected

That's what I thought. I have now fitted another known working fan switch so fans are working correctly but it is still overheating and reaching 100degC on the dash with the thermostat stuck wide open. What else could be the problem?

[Nick W]

It's probably worth checking the waterpump; the impeller inside the block might be loose and not circulating the coolant. This is quite a common problem on other engines, so might be the case here.
At least that's a cheap check for you to do, and a new pump isn't expensive if needed.

[Andy A]

Thanks Nick for replying. I will have a look into the water pump but when I drove it on the motorway there was no problem with high temps. This points to the pump probably working fine.

[05omegav6]

Thanks Nick for replying. I will have a look into the water pump but when I drove it on the motorway there was no problem with high temps. This points to the pump probably working fine.

Au contraire Rodney, Au contraire...

That confirms pump is shagged as it's the increased airflow from higher speed doing all the work.

The fans will help keep the temp down when in slower traffic, but the fans only kick in when then radiator reaches 100 degrees. Could also be the ecu coolant temp sensor playing up...

What state is the coolant in?

[Andy A]

Thanks Nick for replying. I will have a look into the water pump but when I drove it on the motorway there was no problem with high temps. This points to the pump probably working fine.

Au contraire Rodney, Au contraire...

That confirms pump is shagged as it's the increased airflow from higher speed doing all the work.

The fans will help keep the temp down when in slower traffic, but the fans only kick in when then radiator reaches 100 degrees. Could also be the ecu coolant temp sensor playing up...

What state is the coolant in?

It was very clean to start with red coolant additive. But just to make sure I flushed out fully and put in proper VX coolant anti freeze 50/50 and tested. Heater matrix flushed and blowing very hot. Radiator flushed and hot with no cold or warm spots, just hot all over. Even flushed the engine through and it was fast flowing and very clean.

Can anyone help with my 2.6 overheating problem please?

Any help is really appreciated.

Thanks

[Andy B]

....
Can anyone help with my 2.6 overheating problem please?

Any help is really appreciated.

Thanks

How about Al's suggestion of a fubar'd pump 

[05omegav6]

Actually Nicks suggestion I merely explained why...

[Andy A]

I tested the pump and the pump is fine. 

I still think its to do with the fan switch's. The old one is definitely dead and the new one I bought was turning the fans on at a much higher temp that it should. This is what I believe is happening. I'm sure its faulty.

I then got hold of and tried a known good one that was working when it was taken out of the engine over 4 years ago. I now think this is switching the fans on at a much higher temp that it should. I believe this is faulty as well.

I have a friend is bringing his 2.5 down today and that is running at a perfect temp.

I will try his switch and hopefully put this problem to bed, once and for all. My gut feeling is that the switches I have tried so far are all faulty. Its the only explanation that I can come up with.

[omegod]

I tested the pump and the pump is fine. 

I still think its to do with the fan switch's. The old one is definitely dead and the new one I bought was turning the fans on at a much higher temp that it should. This is what I believe is happening. I'm sure its faulty.

I then got hold of and tried a known good one that was working when it was taken out of the engine over 4 years ago. I now think this is switching the fans on at a much higher temp that it should. I believe this is faulty as well.

I have a friend is bringing his 2.5 down today and that is running at a perfect temp.

I will try his switch and hopefully put this problem to bed, once and for all. My gut feeling is that the switches I have tried so far are all faulty. Its the only explanation that I can come up with.

How did you test it?

[Andy A]

On my 2.2i when I flushed the coolant I pulled of the small return pipe that connects the the expansion tank and monitored the flow at different rpm's.

I did the same with this one and it was a good flow rate match. 

[Andy A]

Swapped over the fan switch from my friends engine and now the fans come on when the car is parked up at around 93degC and shut off at 87degC on the dash. Took the car for run and as expected with air flow the car runs cold because the thermostat is stuck wide open. I will buy a genuine fan switch from VX tomorrow.

Talk about unlucky.

Thank you all for all your help and advice.