Vauxhall Astra G Petrol - Over heating astra

Honest John Back Room » Technical matters
What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks
View Threaded
Fri 11 Nov 2016 13:53
Vauxhall Astra G Petrol - Over heating astra - Jonathan buchner

I need advise please

My Astra g is over heating. apon start up all is good. the temp gauge takes along time to even move to the first notch. as the car heats up, the gauge quickly moves up to 80 and the water in the reservoir starts to boil and steam out.

The fan doesn't come on, And I don't know if this is because the gauge only goes to 80before the water is boiling. the heating system inside the car pushes out hot and cold air so no issue there.

I still haven't manually test to d c if the fan is working, but was wondering if the coolant temperature sensor could be the fault?

Any help will b most appreciate.

Thanks

Reply | Report as offensive | Link
Fri 11 Nov 2016 14:39
Vauxhall Astra G Petrol - Over heating astra - Railroad.

If the heater is hot you should be able to cool the engine by using the blower to draw heat. Open the windows, put the heater on hot and the fan on high speed. The engine should start to run cooler and temperature gauge should come down. If it does it's more than likely that the water pump is working as it should.

The most likely problem then is either the thermostat stuck closed or a blocked or deteriorated radiator. Check the radiator fins for condition and change the thermostat anyway. Blow compressed air through the radiator fins if they're in good condition to remove and dirt and dust which may be restricting the air flow. Cooling fan or no cooling fan, the engine will not cool if the radiator is cold when the engine is hot. The radiator is a heat exchanger, and the engine cools by the radiator dissipating its heat into the air.

Reply | Report as offensive | Link
Fri 11 Nov 2016 15:06
Vauxhall Astra G Petrol - Over heating astra - hardway

Well I did a head gasket on one of these then began to slightly panic as I usually run them until the fan kicks in to check the cooling system,

No temp gauge on this one so I had the diagnostics plugged in to monitor actual temperature.

Anyway after mild concern about the high heat/no fan I bought a new CTS and fitted it then re ran the engine,

Well the fans did cut in then out but only at something lioke 96 Degrees!!

Popped the old one back in and it performed exactly the same.

These b*****s really have to get very hot before fans come on and then they do not stay on for long at all.

So I'd not worry about the fan and like Railroad stated check for blocked rad or weak pump.

Reply | Report as offensive | Link
Fri 11 Nov 2016 15:12
Vauxhall Astra G Petrol - Over heating astra - RT

Temperature gauges aren't accurate - they're electronically adjusted and sit at normal for a wide range of actual temperatures - part of the reason Vauxhall dropped them for many models.

Reply | Report as offensive | Link
Fri 11 Nov 2016 15:10
Vauxhall Astra G Petrol - Over heating astra - Jonathan buchner

Thanks

I think the radiator was cold to the touch even though the water pipes we're hot. would u say a failed closed thermostat?

Reply | Report as offensive | Link
Fri 11 Nov 2016 16:04
Vauxhall Astra G Petrol - Over heating astra - Railroad.

Renew the thermostat regardless. It's a waxstat type which means inside the body of it is wax. When the engine gets hot the wax expands and pushes the valve open against a spring. As the engine cools down the wax contracts, and the spring pushes the valve closed. If the engine gets too hot the wax will overheat and get very thin. The liquid wax will leak from the thermostat body and become lost. Having lost some or all of the wax the thermostat will no longer work correctly or even at all.

Reply | Report as offensive | Link
Fri 11 Nov 2016 16:25
Vauxhall Astra G Petrol - Over heating astra - Jonathan buchner

Thanks for the advice. I was trying to only go down this route as a last resort due to where it sits in the engine, but needs must. thanks to all for commenting

Reply | Report as offensive | Link