VT commodore temp rises then lowers wildly ???

[JakeysVT]

when driving the temp rise quite high the other day then it lowered agen but while idling it went right back up agen ? i have tested the thermostat, and drained the cooling system and put fresh water and coolant in it i have also bled the system too so there is no air in it

any help will be much appreciated

[jetboy]

It sounds to me that the thermostat is sticky and is not functioning properly , how did you test it ???? how highs ur temp getting are your fans working ???? . Best way to test your thermostat is to boil the kettle put the thermostat in a cup an pour the boiled water over it , if it dont open toss it . it also might be stuck open this will cause what your describing . For the cost of a new thermostat as opposed to a cooked motor its pretty cheap really . Oh an check ur radiator cap if its crook that will also cause wht u are describing as the recovery system wont work properly

[TonyJZX]

is it wise to use water at all? with coolant so cheap you may as well use 100% coolant?

[JakeysVT]

Hi Jetboy yes i did test the thermostat in the boiling water and yes the fans do work they kick in at about 104 degrees havnt tested the cap how would you test that ? its about a 60% coolant to water mix didnt think you could use 100% coolant :P
thanks for the quick replies btw guys

[lout]

I dont think it is bled properly
and as jetboy suggested i would replace the thermostat for peace of mind
has the car always had coolant in it or just plain water? pump impeller may be coroded

[DLFHUB666]

DONT use 100% coolant. coolant will not work alone ,It does not have the cooling properties of water, but coolant will lower the freezing point of water so that it wont freeze and it also raises the boiling point an has corrosive inhibitors in it aswell. If water didnt freeze at 0 or boil at 100 an carrode the cooling system you wouldnt use coolant at all.

[JakeysVT]

Its always had coolant in it, good idea lout i might go and change it just to make sure and im pretty sure it is bled properly because we used the bleed valve till just water came out of it, isnt that how you do it ? then tighten it back up ?

[lout]

the radiator filler neck needs an adaptor to be higher than the bleeder.and fill slowly with heater set to hot
i like to warm the engine slightly 1-2 minutes to pressurize system then open bleeder again until water comes out, then allow to cool ,open radiator cap and top up, and repeat as required

[JakeysVT]

alright will do that aswell, it did it agen but it just wentstraight to "HOT" and started beeping but stopped for 5 mins with it off then it was fine agen ? really weird stuff haha

[lout]

could also be a faulty sensor, wiring connection

[DLFHUB666]

i know it has been said but sounds like it hasnt been bled properly.

[JakeysVT]

ok thanks guys will get an adapter and bleed the system agen to see if that fixes it, thanks agen for the help much appreciated

[DLFHUB666]

you can just cut the bottom off a 600ml coke bottle an use that you dont need a special adapter.

[JakeysVT]

oh ok cool will do that insted thanks