Temp gauge going nuts?!?

[Timborooni]

Hi all,

Just replaced my radiator, water pump, thermostat, radiator cap and completely flushed the system as i just bought my car a few weeks ago and the water in the "leaking" radiator was just sludge. Now my temp gauge is going nuts, it runs fine and temp is a few millimeters above 1/4 all of a sudden it will rise to hot and then slowly come back down. Have checked for leaks and checked coolant and all is fine and no signs of REAL overheating. The thermo fans also come on but i am assuming this is controlled by the guage somehow?? Could it be the sensor for the gauge or am i perhaps barking up the wrong tree.

Any help would be really appreciated. I have a V6 VT 99 model commodore wagon.

Thanks in advance.

Tim.

[ACEMonkey]

bleed your cooling system again. its probably air trapped in your system.

[mayes]

rooted thermostat?

[Timborooni]

UPDATE - Hoorah!! Problem solved... Thanks for the replies but was at Peps Autos buying a new coolant sensor and the guy suggested i check the heater hoses, now i know i know that shouldn't affect the cooling BUT when he said this it kicked my brain in and i remembered that it was only overheating when the heater was on (driving kids to school etc in the mornings, bloody cold in Windsor) and was fine every other time. Short version, replaced heater hoses and heater switch and another bloody good flushing and YES!!! Have test it all arvo using the hidden temp etc in the onboard computer readout and temp is spot on!! Bloody relief i tell you. Anyway, thanks to all and will be contributing this fantastic site as it has been a godsend since i bought my VT and has allowed me to fix quite a few things myself. Cheers!

[11gothevt11]

I have read up befor on here
Sometimes new termosats are faulty from new???
Boil a pot of water than drop it in and see if it opens
Also there are low tem opening thermosats that you can buy

[vtanthony]

its could be a sign of a cracked head i had the exact problem and the first time it was looked at they found nothing .weeks down the track i took it to get it Co2 tested and they found carbon monoxide coming through the radiator

.how is the car in the morning does it start ad idle rough for a few mins or less then settle .

i bought my vt and had that problem a week after i bought it .under waranty they claimed they found nothing but i knew something was wrong. mine was spitting water out the exhaust manifold in the morning .just before i was going to work i couldnt see it because it was still dark

[wonkaman]

I had the same problem with my VX replaced the radiator because that had split was told it was a faulty thermostat had caused problem and then discovered I had a cracked head after thet radiator lasted three weeks. Apparently its a common problem withy them cracking between the valves they also have a problem with warped heads. I would suggest using a lower temp thermostat so the engine runs a bit cooler. Hope we have all been of assistance