over heating

[crew.man]

hey guys im one of those who loin the site when they need help and rarely look around on it after. i will be the first to admit.....
but in saying that i need some help and thought you guys would be able to produce that.
99 vt series 2 v6 auto. i was taking the gf to work this morning and after about 10 mins of driving the warning light came on saying "HOT" i looked and the temp gauge was ojust over 3/4 so i let it cool down and topped it with coolant and got another 10 mins out of it b4 i had to stop and repeat. any hits? plus air con doesnt work but i think it just needs re-gassing.
engine fans work though so it tries to cool down
oh and about 2 weeks prior the heater slowly stopped working. cheers guys i will appreciate any help at all.
Pete

[accentstencil]

It could possibly be that the thermostat is not opening as it should. You can test it by removing it from vehicle and putting it in a pot of water on the stove. Heat the water and if you have a thermometer, the thermostat should begin to open at between 89 - 93 degrees C and should be fully open at 106 degrees. If it doesn't open properly, replace it.
Your problem could also be air in the system which can be fixed by bleeding it.

[ACEMonkey]

Its a little hard to boil water to 106 degrees as water already boils at 100, but nonetheless your thermostat should still open.

[crew.man]

ok as im not that mechanical minded you will understand me when i ask as to where the thermostat is situated and what it looks like

[WAGON MAN]

Its a little hard to boil water to 106 degrees as water already boils at 100, but nonetheless your thermostat should still open.

If he put some salt into the water,

it would raise the boiling point of the water above 106 degrees.

[accentstencil]

ok as im not that mechanical minded you will understand me when i ask as to where the thermostat is situated and what it looks like

The top radiator hose connects to the thermosat housing. Undo the 2 bolts that hold the housing in place and you will find the thermostat in there. Take note of which way it sits.

[commsirac]

Id only bother taking out the thermostat to test if there are symptoms that show that it is at fault.
What to look for: engine getting hot and radiator staying cold. If the bottom hose of the radiator is noticeably colder than the top hose when the motor is in overheat conditions, then not enough coolant is circulating. This could be due to clogged radiator, water pump, partially closed thermostat or other restrictions. Better still actually get infra red temp gauge to test these points for accurate diagnosis within a matter of seconds.

The heater not working may be related in that circulation pressur isnt good enough. (ie prob with pump)

[Holdens Rule]

My guess if the heater isn't working is the water pump. I'm saying that cause a few weeks ago my mechanic had a VT come in with the same problem, after a lot of rooting around and checking various things he found the water pump had all its fins worn down so it wasn't pumping water around the engine.

[Harvs82]

Its a little hard to boil water to 106 degrees as water already boils at 100, but nonetheless your thermostat should still open.

Actually if your cooling system is filled with the proper coolant concentrate and water mix, and not just water, then you will find that the boiling point of the coolant is much higher than 100 degrees C. The other point to note that the system is under pressure, which further raises the boiling point again. Assuming that the radiator cap is working properly and the coolant mix is correct then the coolant will actually boil at around 135 degrees celcius!


I'd be doing a full cooling system flush in this case, and replacing the thermostat at the same time. If the engine hasn't had the coolant changed in a long time, or its just running straight water, there is every possibility that the fins on the water pump have rusted away, and that the radiator is clogged up with rust and scale too. If the car is still running too hot after that, I would suggest that either the cooling system or radiator is blocked, or the water pump is buggered. New water pump for the ecotec 6 is only about $80 anyway, so its not a huge expense, but you do need to flush the cooling system and then bleed it after installation.

[vxcalais_01]

Actually if your cooling system is filled with the proper coolant concentrate and water mix, and not just water, then you will find that the boiling point of the coolant is much higher than 100 degrees C. The other point to note that the system is under pressure, which further raises the boiling point again. Assuming that the radiator cap is working properly and the coolant mix is correct then the coolant will actually boil at around 135 degrees celcius!


I'd be doing a full cooling system flush in this case, and replacing the thermostat at the same time. If the engine hasn't had the coolant changed in a long time, or its just running straight water, there is every possibility that the fins on the water pump have rusted away, and that the radiator is clogged up with rust and scale too. If the car is still running too hot after that, I would suggest that either the cooling system or radiator is blocked, or the water pump is buggered. New water pump for the ecotec 6 is only about $80 anyway, so its not a huge expense, but you do need to flush the cooling system and then bleed it after installation.

I always understood that that figure was its boiling point, so coolant plus the pressure from the cap actually only caused it to boil at 120 degrees plus ? The whole idea is to stop it from boiling. Water on its own pulls more heat than when its mixed with coolant, but it boils too readily. Coolant and pressure from cap raise the boiling point. Coolant also reduces its freezing point to below zero as this is when water freezes. Ice already starts forming at around 3 degrees.

[commsirac]

I always understood that that figure was its boiling point, so coolant plus the pressure from the cap actually only caused it to boil at 120 degrees plus ? The whole idea is to stop it from boiling. Water on its own pulls more heat than when its mixed with coolant, but it boils too readily. Coolant and pressure from cap raise the boiling point. Coolant also reduces its freezing point to below zero as this is when water freezes. Ice already starts forming at around 3 degrees.

I dont really understand the point of your post vxcalais. Are you just restating what harvs has already said.

You could always research the issue?
100% ethylene glycol has a boling point of 195C and 50/50 water mix has a boiling point of 107C at atmospheric pressure.
Each rise in pressure of 1psi will cause an increase of the boiling point by 1.4C for water and about 1.5C for the glycol mix.
Water does have a higher heat capacity than a 50/50 mix. This would be relevant to cooling capacity if we were not getting rid of the heat from the water.
However, that is not how a commodore or any other water cooled engine works, it is done by exchanging the heat to the air. While it takes less energy to heat up the same amount of glycol mix as water to a particular temp, it is also loses temperature more quickly as it goes through the radiator and even more quickly if it goes in at a higher temperature. To cater for the quicker rise and fall of the glycol mix's temperature the water pump simply has to run faster than if it were for straight water. Modern engines will not run cooler on straight water. However, some older cars with marginal cooling systems are at risk of overheating on a 50/50 mix if they were designed for straight water simply because the water pump isnt going fast enough.