7mge - Overheating - radomly.

[79GT]

Hey guys,
So here is the deal, bought an mx83 did the headgasket, all sweet. car overheated constantly. assumed very blocked water galleries. FLushed system. then it was all good for 3 weeks.

Suddenly car overheats, carry out normal checks, radiator isnt hot, fluid is not low, top hose is pressurised. Released the pressure, refilled. water seemed to be being pushed out the top of the radiator...confused. Let it do its thing for a litle bit, turned the car off, refilled again. car seemed to be running fine at idle, took off and in 30 seconds of driving, car overheats again.

Pull over - carry out normal checks, radiator is cold. release the pressure, fill up system again, turn around and head home. car runs fine, no worries, no overheating. all sweet. get the 7 minutes back home. grab some more tools, and head out again...just incase to test it and get were i need to be. car worked fine no worries. this was thurs arvo taken the car on 2-3 trips since then, no sign of overheating.

could it be an issue with my water pump.
could it be more blockages in the system.
any help would be appreciated.

Cheers.

[ollie83]

thermostat?? engine is getting hot, but the rad is cold... possibly stuck closed?

[79GT]

thermostat has been replaced, unless it has screwed up again...likelihood of that happening??

[crowncustom]

Don't be suprised that your new thermostat isn't stuffed.Wont be the first or last time that this occurs.
Just pull the thermostat out and test it.
Cheers Brett.

[Guyana00]

Is it staying up high or going up and down? If the latter it could just be air.

[79GT]

Its really quite weird, The temp would start rising, and continue to rise at almost a steady rate.

Then i would turn the car off as i rolled to a hault. get out of the car and pop the bonnet. I would then turn the key back to the on position and the temp would be normal again....could my temp sensor be fcuked...

It actually would make sense now i think about it.

[river]

Hi,

Remove the thermostat. The engine should not get up to temp. If it still gets hot then you have an issue with some blockage in the radiator or water galleries in the engine.

If the engine does not overheat, then you can assume the thermostat was not operating properly.

Removing the thermostat won't fix your problem, but it will at least point you in the right direction.

seeyuzz
river

[79GT]

cheeeeeers, will investimagate.

[Guyana00]

Good suggestion. If it still overheats and and it's the original rad they get clogged and pretty much just can't be cleaned out. Get a replacement.

About the air, since you did a flush I recommended that. Also happens easy on the 7Ms because of BHG and air gets in, but you said you took care of that.

Drive the car, when it overheats turn the engine off and power back to on, see what the needle does. If it doesn't fluctuate it can be the air because the engine isn't cycling. You have some options now.

[river]

Hi,

Any update on this?

seeyuzz
river

[CrUZida]

Just a note to anyone reading this, whenever you do any major work on the cooling system (head gasket, new water pump, or even an engine swap), get the radiator cleaned.

Assuming they don't stuff the core when removing the top tank (which is a possibility) then its about an $80 cost.

Cheap insurance.

[Pimpin_1JZ]

I'd also put it done to a sticky thermostat. Boil a cup of water, drop the thermostat in and watch to see what it does. I'd say more than likely it is your problem.

[kickstartRA28]

If car has overheated before radiator will have picked up debris from engine and will cause blockage in radiator......get it cleaned out.

[Bananaman]

Did you make sure to get all air out of the system? Not getting airlocks?

[79GT]

hey guys, had a chance to have a proper look at this. guess what lucky me, i have bubbles coming up through the radiator. the car has done about 1050-1100ks since the engine was put together. it was due for a retorqueing but i didnt think it would pop a head gasket sooooo soooooon.

I am gonna try retorqueing the head before i go any further and see if that helps, but otherwise. back to step one again....sigh....