Temperature Light and Gauge Hitting H but engine or radiator not hot...

[Harry Krishna]

Hi,
I have a 2002 Holden VX Calais. Over the last week a couple of times the temperature light has come on and the temperature gauge has hit the H mark. When I pull over and look under the hood there is no steam or heat and everything looks ok. The only thing is the one of the cooling fans is spinning (loudly) and the second one isnt. Its only after about 10 minutes of driving. When I get back in the car and drive off after a minute or two the temperature gauge drops down to normal and everything is fine.

It's intermittent too... only happened 3 times out of about 15 seperate drives over the last week. Some short distance, some long....

So not sure if this an easy one for you or not....I know its hard to diagnose without seeing the car but if anyone could give some indication of the problem and possible cost that would be fantastic !

Cheers

[astormsau]

There are 2 coolant temp sensors on the VS... I expect this is the same on the VT.

Assuming the car is not overheating consider the following;
1 sensor sends a signal to the guage in the dash, the other sends a signal to the computer to control fuel mixture and turn on/off the fans, they have separate wiring circuits.
The one for the dash has a simple rectangular clip which goes over the end of the sensor, the one for the computer has a 2 wire connector with a clip.
They are located right next to each other, on the motor, below the thermostat housing where the top radiator hose exits the motor.
There is a chance that either the sensor or the wiring to the sensor is playing up for the dash circuit, this is causing the problem you are experiencing where the guage goes crazy.
I would start by inspecting the wiring and perhaps replacing the sender, its about $15 from Holden.

If the car is actually overheating then it is possible that the second sensor is playing up causing the car not to turn on the thermo fans.
A simple test is to disconnect the computer sensor wires from the sensor and then start the car, the car will start and then within a few seconds the fans will turn on, first at low speed and then at high speed.
This is a rough test to tell you that the fan circuits and associated stuff in the computer is working correctly. You will also get a check engine light on the dash to tell you that the computer isn't getting signal from the sensor.

Hope this helps you diagnose.

Drew

[Dayvo]

Check the coolant level and condition in the radiator and overflow bottle.I'd be tempted to flush the cooling system if it hasn't been done for a while and don't forget to bleed it too.

[chargedvx6]

If it happens in the 1st 10 or so minutes after starting to drive from cold it will be a sticky thermostat. Very common on commodores and the symptoms sound like that's what it is

[Harry Krishna]

Hi all... thanks for all the information.. I suspect it is either the thermostat or one of the sensors... doesn't sound like a costly repair so I'll take it to the local mechanic... the car is certainly not running 'hot' and in the last 3 days hasn't done it again so its only intermittent.. but still will get it checked out. Will also get the radiator flushed and re-filled the last time I had it serviced they recommended this and with summer coming up better do it now... thanks for all the replies... doesnt sound too expensive !

[tairvine]

Harry,
I have exactly the same problem to yours. You've described what's happening to me down to a tee. If you find out what the cause is, could you let me know?

Thanks
Tom

[hug624]

I had the exact same problem. It went away when I topped up the coolant via the radiator cap, I think the problem is accumulated gunk blocking some part of the coolant system, probably the connection between the radiator and coolant tank.There was a bit of gunk floating in the system, I haven't flushed the system yet but I think that should solve the problem properly.

[Harry Krishna]

Hi, I ended up flushing the radiator out and topping up with new coolant... when I examined the fluid from the radiator and the subsequent flush there was indeed quite a bit of 'gunk' for want of a better word !!!! So i suspect that it has been a long time between flushes for the radiator (I certainly havent had it flushed since i got it over 4 years ago).... so I think a bit of 'gunk' must have gotten stuck somewhere... because now it works PERFECTLY and i haven't had any problems since the flush... (although I did notice a bit of a strange smell for the first few days... but thats gone too...)