radiator overheating when i turn the car off -__-

[sully1997]

hey guys,
im sure a few people have had this problem before,
but everytime i park and turn the car off the coolant comes to the boil and usually starts pissing out of the overflow.

i have recently flushed the radiator and used high pressure through it clean it properly,
it has had the radiator cap replaced and pressure tested and no leaks.

any idea what might stop it ??
cheers guys

[VrWagz1]

You have a tiny pin hole leak somwhere, possibly around a hose clamp that is old and rooted (lost its springyness) and dosnt pull tight right the way round the hose when you tighten it up or the thermostat housing aswell. Inspect everywhere, as it maybe so small you wont see the coolant, but you will see a white mark where its escaping and dryingup.

[Brett_jjj]

When an engine is first shut down,the coolant temp actually rises a bit as theres no longer any coolant being pumped around through the cooling system to disperse any heat away from the engine block and heads,so the coolant thats around the block and heads gets a bit hotter for a few minutes after the engine is shut down.This causes the cooling system to pressurise more then when its running for a few minutes after shutdown..Id firstly be checking the radiator cap again,some people have had problems lately with Trident brand radiator caps not holding their pressure properly and not sealing properly which causes the coolant to overflow back to the overflow tank, and then once the overflow tank is full ,out onto the ground..The CPC brand radiator caps are a lot better and were the brand of the cap that was fitted originally to these cars.Id get one of these CPC brand caps and see what happens then.

[VrWagz1]

Contrary to Bret_jjjj i would steer well clear of CPC caps. They are the reason i had to get my tanks resoldered recently. The rubber gasket on them is way to soft. Mine grew up the neck of the inlet and blocked off the overflow Not sure what brand i have now, but i made sure it had a much tougher rubber seal on it that wont spread.

[m1lky]

My vs did this exact thing. Replaced radiator cap and never did it again

[monkeys437]

My missus car was doing this a while back. Turned out it just needed the cooling system bled properly

[Brett_jjj]

Contrary to Bret_jjjj i would steer well clear of CPC caps. They are the reason i had to get my tanks resoldered recently. The rubber gasket on them is way to soft. Mine grew up the neck of the inlet and blocked off the overflow Not sure what brand i have now, but i made sure it had a much tougher rubber seal on it that wont spread.

If you've only have had one CPC radiator cap fail on you,then this doesnt prove that all CPC brand caps are the same, and is certainly no reason to stay away from this brand..Ive read quite a few cases here on JC,where people have had problems with Trident brand radiator caps,and most of these people who posted about this problem,fixed it by fitting CPC brand caps which are apparently the genuine cap originally fitted to these cars.Ive had a CPC brand cap on my VSV6 for 3 years now and it doesnt have soft rubber or whatever.Ive just had a look at the two different brand radiator caps,the Trident and CPC brands, and the caps rubber seal material looks and feels to be about the same softness on both brand caps.I dont think Ive ever read one complaint on here about CPC brand caps.Im not too sure how many other brands of radiator cap are out there besides these two.I know both of these are pretty common.

[sully1997]

alright, thanks for your help guys,
i'll have a closer look at it and see if i can find any leaks but i got a CPC cap and the problem continued, it might have just been that by the time i replaced the cap i had topped it up with water to many times so the coolant isnt actually working properly, hopefully if i give it a good flush and put some 90 plus in it it will fix it

would there be any point putting the red type coolant in it, i no that vz's have to have it cos its an alloytec motor, would it be bad in an ecotec motor ?

[m1lky]

Even with completely water it still shouldn't get hot. Personally I'd sort the problem before I paid for more antifreeze that you could just loose again.

Main purpose of anti freeze is freezing conditions and corrosion protection

[Brett_jjj]

Yeah,if its not the cap failing to hold pressure, then its something else,and as mentioned,even with plain water in the system,it shouldnt overheat.Does the cooling fan cut in at all?Does it come on when the A/C is switched on?

[JJ's VR]

hey guys,
im sure a few people have had this problem before,
but everytime i park and turn the car off the coolant comes to the boil and usually starts pissing out of the overflow.

i have recently flushed the radiator and used high pressure through it clean it properly,
it has had the radiator cap replaced and pressure tested and no leaks.

any idea what might stop it ??
cheers guys

I agree with monkeys437, If replacing radiator cap hasn't solved your problem, it sounds like you've got air trapped in the engine block. Did you bleed the cooling system after changing coolant etc? You need to bleed it from the highest point on the cooling system, with the engine running and at operating temperature and also with the heater turned up full ball (not fan, just temperature control dial, turn fully into the red) then on top of your thermostat housing is a knurled screw, undo it (not all the way, one to one and a half turns is enough) once correct conditions are achieved and you'll see and hear the air gush out. Then tighten screw back up tight. Be careful not to get burnt from expelled hot coolant, I usually place a heap of rags around the area and use a long screwdriver!!!! If nothing comes out, then your thermostat is stuffed! Not opening. Around the $15 mark from memory. Was the thermostat replaced as well? Whatever you do, DONT put the red coolant in your motor!!! Thats why they are red, for quick reference as to what type of coolant it is!! You need the green stuff :-) the red stuff may destroy o'rings, gaskets and worse case scenario, destroy your heads Good luck buddy.

[VrWagz1]

I agree with monkeys437, If replacing radiator cap hasn't solved your problem, it sounds like you've got air trapped in the engine block. Did you bleed the cooling system after changing coolant etc? You need to bleed it from the highest point on the cooling system, with the engine running and at operating temperature and also with the heater turned up full ball (not fan, just temperature control dial, turn fully into the red) then on top of your thermostat housing is a knurled screw, undo it (not all the way, one to one and a half turns is enough) once correct conditions are achieved and you'll see and hear the air gush out. Then tighten screw back up tight. Be careful not to get burnt from expelled hot coolant, I usually place a heap of rags around the area and use a long screwdriver!!!! If nothing comes out, then your thermostat is stuffed! Not opening. Around the $15 mark from memory. Was the thermostat replaced as well? Whatever you do, DONT put the red coolant in your motor!!! Thats why they are red, for quick reference as to what type of coolant it is!! You need the green stuff :-) the red stuff may destroy o'rings, gaskets and worse case scenario, destroy your heads Good luck buddy.

WTF theres no bleeder screw! What r u on about???

[m1lky]

Should be on the thermostat housing. At the end of the top hose

[barnsey91]

yeh just bleed it properly, i had the same problem

[sully1997]

alright, thanks for your help, yeah i i bled it the first time but i think i needa do it again and i didnt do it with the heater fully turned up so ill try that and i'll use the 90 plus probs
much appreciated

[Brett_jjj]

When you refill the radiator, park the car so the front end is up higher than the rear.(car ramps?).This will cause any trapped air in the engine block to come forward to the front of the engine and to the radiator where it can be expelled from the cooling system.Ive replaced the coolant in these cars heaps of times now,and I never use the bleeder screw,just have the front higher than the rear like I mentioned,and thats it,just refill it.Ive never had one car overheat or have problems with trapped air when refilling the radiator this way.Also make sure that the interior heater is set to hot, as the heater system is part of the engines cooling system and having it set to hot will help purge any trapped air in the heater core or hoses etc..

[The1]

Whatever you do, DONT put the red coolant in your motor!!! Thats why they are red, for quick reference as to what type of coolant it is!! You need the green stuff :-) the red stuff may destroy o'rings, gaskets and worse case scenario, destroy your heads Good luck buddy.

Coolant colour has nothing to do with it.

Coolant for ecotec is holden HN 2043 which is type A. I use tectaloy big red / hi load which is type A but red in colour, it also has a indicator colour so when the coolant starts to change colour the ingredients arn't doing they job anymore.

Some reading.
Electrolysis in the cooling system - Ford Forums Online - Ford Discussion & Enthusiast Forum