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[irratic]

2.5 omega elite, 98.
  car runs normal temperature untill i use the air con. then after a run its running in the red, turn off the air con with the eco button and temperature start to come down settling about 100.. turn air con back on and it starts to climb... all fans are working and as the car usually sits just below 100 i assume the stat is working ok... any ideas any one? thanks

[darren5354]

hi irratic, I am no expert so take what I say with a pinch of salt, there should be a refrigerant condenser connected to the top right hand side of the radiator. while the engine is running at normal temp and the air con is on, this should remain very cold. if it is warm there may be a fault there that isn't allowing the water to circulate the engine/radiator.


anyway just a thought & good luck

[irratic]

cheers mate, i'll have a look at it, i was thing that there maybe a bypass valve that wasn't working... it gives me the impression that when the a/c is on it stops the circulation.. if you switch to a/c when the engine is hot the temperature climbs alarmingly fast..

[razzo]

could this be a faulty HBV as it is supposed to stop coolant flow into heater matrix when aircon is working

[irratic]

ive been loosing some coolant, which i thought could be the HBV valve at fault.. if that also alters the flow when the air con is on.. it could well be....

[markrl]

Check that the two Auxilairy Fans are switching on in front of the a/c condensor behind the grill. They should come on together slowly at first then fast as the temp and a/c gas pressure rises. (just sorting out a small problem I have in this area myself). There are 3 fans in total and a rather complicated circuit of temp sensors and pressure switches with a small test point in the relay box next to the battery.  

[irratic]

all of the fans are runnig. thats what the problem is.

[Admin]

No, your problem is that your engine is running way to hot to start with!

It should run at 92-94 normally (on pre facelift).
When was the coolant last changed and properly flushed out?

Start with draining coolant then flush out thoroughly (please tell me you have not been running just water).
I would recommend using a proper coolant flush to really clean things out.

Then once clean fill with 50/50 mix and run it.

As for the coolant loss.
It could be the HBV. Look for water around the back of the engine on the drivers side, often drips down the bell housing.
If it is the HBV then also you are likely to get overpressurising of the system as air gets in and causes lots of problems.

[irratic]

its not been drained since ive had the car. no, its about 30 to 40 percent antifreeze.... whats the best way to flush it out? put a hose pipe on tyhe block and wash it threw with tap pressure??

[Dave-C]

Hi Russ,  watching this thread very closely!!!  Having a similar problem on my Elite...  it's sitting at about 98 deg's when running at normal temp.. had a new water pump belt n' coolant several months ago..   flushed and reverse flushed the rad really well...  it appears really clear, no cold spots!!!!..  doing my gearbox fluid tomorrow by the way...  all the above for towing again soon!!!  Keep us updated with your progress...

Dave C

[TheBoy]

I rate the Forte Cooling System flush. Good, but bloody expensive!

[Dave-C]

I rate the Forte Cooling System flush. Good, but bloody expensive!

I only had hot probs since I flushed the system 12 mnths ago, the red light came on whilst towing and it spat some box fluid out...  wondering if I've partially blocked my rad, causing the box to overheat...  thinking of taking the rad off and Fernoxing it,, heard the Forte is good from many other folks....   may try that myself too...

DC

[Matchless]

Overheating when a/c switched on and / or towing (auto box).

This is telling you that your cooling system is only just coping under normal circumstances due to : clogged radiator waterways / choked radiator or condenser air-ways / corrosion or lime deposits in engine waterways / poor fan performance / etc.

When you run the a/c the condenser in front of the radiator raises the air temperature a few degrees before it reaches the engine cooling rad.
When you drive hard or tow with an auto box the autobox cooler dumps more heat into the coolant.

The thermostat controls coolant temperature by varying the flow rate, if the system is not working efficiently then the thermostat will already be wide open under normal conditions...add some extra themal load and there is no extra flow rate available to increase cooling capacity so the temperature starts to rise.

So make sure the fins are clear on both condenser and radiator. Flush coolant system with something designed to remove limescale and oil residues. If all else fails, fit a new rad.

[Mike Collins]

Just a thought, if cooling ok when a/c is off, HBV will be letting your heater matrix act as a cooling radiator. Turning on a/c causes the HBV to stop flow through the heater. If your main radiator is is partly blocked, either internally or to airflow, now you have only a restricted coolant radiator to cool the liquid.

I had a bout of very hot running some years ago on a 2.5 that was finally cured by removing the coolant radiator, flow testing and replacing the core.