VT overheating

[Malcolm Logan]

I may have done something real stupid! I added coolant through the radiator cap instead of the reservoir. A day or so later the temperature cycles high-medium-high. I engaged my brain and started to fault-find, I has about to remove the thermostat and saw the air bleed valve. I have parked on level ground, started the engine, opened the heater, waited for the temperature to rise, felt pressure and heat in the radiator inlet hose then released the bleed valve. After several minutes and 3-4 attempts air is still blowing out.

Have I blown a head gasket?

What is the best course of action?

[MoSkA]

Keep filling the radiator with coolant till it can't take no more, turn it on for a little while then stop it. Open the bleeder valve(s), put you're mouth over the radiator filler and blow.
I had a problem with my bro's VX, I forgot to turn the cap when I took it off to check the level (I forgot that you don't need to take it off). 20 mins down the road I could smell burnt coolant and a lot of steam from the engine bay, coupled with mass overheating. Turns out all the water had come out of the system.
Went to a servo filled it with water till it overflowed from the radiator.. opened a bleeder and got nothing but air. So I blew in the radiator openeing till water came out, closed the bleeder and topped her up.
Drove it home and didn't drive it again till I took it to Holden for a complete drain and refill.
My main concern was cracking the head because I put water in a very very hot completely dry system, as soon as it got into the actual engine the water immediately started boiling. (like when you put a teaspoon of water on a hotplate).
If you're concerned, take it to Holden.

[9C1pack]

When refilling an empty cooling sytem, the panel shop I worked for used the following method.
Open the heater tap (turn the heater control to the red area).
refill the system with the coolant mix.
Run the motor with the radiator cap off,
As the engine warms up, the thermostat will open, letting air trapped in the engine block come out through the open radiator cap hole, it may take 5 or 10 mins for the engine to "burp" out all the air as each time the cold coolant hits the thermostat it will close, until all the coolant is the same temp and the thermostat stays open.
Then replace the radiator cap, allow the cooling system to build up pressure and visibly check for leaks, especially at hoses/housings that you may have had undone.
Be wary of moving belts and fans, as thermo fans may start up unexpectedly.
If there are bleeder valves, of course open these before the coolant gets too hot or you may get burnt,
The blowing (while the coolant is cold) method, mentioned in the post above, sounds like a good idea also.
On some cars that had the heater in odd spots, it was sometimes nescessary to slip a heater return hose off momentarily to allow trapped air to escape (before the coolant gets too hot)
You can trouble-shoot air in heaters or faulty heater taps by feeling the hoses, if all is well they will feel the same temp as the radiator hoses, if blocked or full of air they will feel cooler. Sometimes squeezing the hoses is enough to burp the air on further in the system to where it can find its way out.
If you have to add water to an already hot engine, do it while the engine is running and add it slowly as there is a risk of cracking blocks and heads and also of boiling water erupting out the filler hole and scalding you, better to wait for it to cool naturally, much safer.
I always check my vt coolant via the radiator cap (when cold) as I do not trust sealed sytems, how they work is, as the water expands with heat, it is pushed out into the radiator overflow bottle, when the engine cools, it is sucked back into the engine. If you get a small leak in the system
(EG:pin hole in radiator or hose), then when it cools, air is sucked back in via the leak. So when you check it via the dipstick in the overflow reservior, all seems ok, but the engine can be half empty.
Just my 2 cents worth, not claiming to be an expert.

[MoSkA]

Yeah good point about making sure everything is cool before puting your mouth over the radiator.
When I said run it then stop it, I mean like a minute just to get things flowing...
Even though I put fresh water in the radiator, I can still taste coolant whenever I lick my lips. I did this 3 weeks ago.

[Coolvx]

Hi Malcolm

The way to bleed the cooling system is

1 Turn heater on then open or remove the bleeder and fill the radiator until a steady stream coolant comes out from the bleeder. ( this may take some time )

2 Close bleeder and start motor, then add more water to radiator if the level drops.
When radiator is full, close the cap and let the engine reach normal or above normal operating temp.
If you here any strange noises during the warm-up dont be concerned but switch the motor off and feel the top radiator hose. If it is hot then thats good but a lot of times the hose is still cool and it sucks itself in, this tells you that the thermostate has opened and the water has gone into the block which causes a vaccum as it cools the block temp.


3 Carefully remove the cap then start the motor and fill the radiator.
When the radiator is full replace the cap and check the temp gauge and if everything is ok then the normal running temp should be seen.

4 Now is the time to fully bleed you system.
With the motor not running carefully release the presure and remove the cap, open the bleeder valve and continue to fill the radiator until a steady stream of water is comming out. ( If the water is spitting out then there is still air in the system ) Then start the motor and do the same thing. ( no spitting ).

5 Close the bleeder and refit radiator cap, fill the overflow bottle and test drive the car . If everything is ok then normal running temps should be seen.
If engine is still overheating then do steps 3 and 4 again.
I have seen mechanics do this 2 or 3 times before all the air has been purged from the system.

6 After the engine has cooled over night or at least 3 hours check the water level in the radiator.

7 JOBS DONE

8 NEVER OPEN THE BLEEDER WHEN THE MOTOR IS RUNNING AND THE COOLING SYSTEM IS UNDER PRESSURE.

Hope this helps
Ron R

[pizzo]

could be low fan speed realy playing up