Engine 'saying' its overheating

[Chalky01]

Heyy all and thanks in advance who can offer any help. Just recently my car all of a sudden displays that its quite hot. So hot infact that it surpasses the actual H on the temp gauge. Now while this is happening, i've jumped out of the car and used a laser temp sensor. It displays that the temperature is only 87 degrees. Now to my understanding the average temperature of the Commodore VS running temperature is 108.

Ive bled the non existant air out of the bleed valve above the thermostat and also we've replaced the sender unit (or thermometre pin thingo) and still it displays that its hot .

Thanks to anyone who can help, and sorry if this questions already been answered .

Matt

[Vee-ard]

replace your temp sender unit.

[Chalky01]

Im under the impression that this is a Temp Sender Unit. Am i correct? lol if so i've already replaced it. Thanks for your help

[BlackVXGTS]

Try replacing the coolant temperature sensor. That's what tells the PCM/ECM how hot the coolant is and when to turn on the fans. First, check that your fans are working properly, both low and high speed. If your coolant is really getting that hot I would have expected coolant to have been forced out of the tube in the overflow tank onto the ground especially when you turn the engine off.

[Chalky01]

Well thats what i mean, its not getting that hot. I could even touch the radiator cap with my hand just afterwards.

[aceventura]

Maybe it's just your gauge?

If you have a multimeter, next time the engine is hot, record the resistance between the centre pin of the temp sender and the outer part (or the block for that matter). I can do the same for my car - this will tell you whether or not the temp gauge is the problem.

[Chalky01]

Thanks!! Would you be able to do that for me mate? It would be a great help!

[keygen]

i just emailed you a multi-meter .
shudn't take too long to get there as i'm in rocky

[Chalky01]

Lol thanks, ill start using my atomiser to produce it so i can use it!

I've got a multimeter, i meant the reading of the resistance on the Temp sensor unit.

[hako]

The 108 deg running temp of an Ecotec is at the thermostat housing and you have to measure the actual coolant...but anyway thats irrelevant. Your problem is that you have either a dead short or an open circuit somewhere in the temp gauge circuit. This causes the gauge to go straight to H. Usually it will be where the cable connects to the sender - the wire can break internally and the insulation will appear to be perfect. If not there then I'd check further along the cable.

[Chalky01]

Thanks mate! ill give it a check.

[aceventura]

Ok, I took a reading as of the temperature sender as the fan came on (105 C) - at which point the gauge was reading half way and the sender was reading ~80 Ohms (make sure you disconnect the lead here or your measurement will be screwed up by the resistance of the gauge).

From memory at ~25 C my sender reads about 2200 Ohms - but don't quote me on that.

But is the car reading hot all the time (even when it is cold)? If it is I tend to agree with Hako, the sender wire is earthing onto the block somewhere making the gauge read high.

[chrisdoesitbetter]

the temp SENSOR actually reads how hot the coolant is and the SENDER sends a signal to your dash, so if u replaced the sender and nothing try replacuing the sensor...i read on here they are about $100 from a holden dealer