VH Overheating when using heater

[ezkii]

Hi,

My VH SL/E runs fine but when i turn the heater on the gauge says its overheating then takes about 5 mins to come back to normal temp range after i turn the heater off. The car doesn't seem to be overheating when this happens tho? The other prob is that even tho the heater is on it does not heat up and just blows cold air.
Have only just got the VH and can't find a Gregorys manual or anything to see what could cause these problems, i'm pretty simple when it comes to this stuff.

Any help is appreciated, Thanks.

(P.S. the radiator has water, pipes are only 2 years old as is the radiator, )

[commsirac]

Sounds an interesting problem. 6cyl or v8?
Havent really heard of it b4, but will give it some thought.
Here are some things that you can check that may provide some insight on what the problem is:

1. find the hoses that go from the motor to the heater box under the bonnet
2. are they cold or warm when you dont have the heater switched on, and compare how warm they are when you do have the heater on.
3. when the temperature gauge goes high after switching on the heater check how hot the bottom hose of the radiator is......is it as hot as the top hose.
4. start with the heater on when you start the motor from cold, does it do the same thing.
This would tell us something about the thermostat, it may suffer some sort of closure when the cold water from the heater circuit first comes in contact and then take time to re equalise again.
Replacing the thermostat isnt a difficult or expensive job.

5. are there other water hoses that run off the motor, bypass hose or lpg or manifold heater?

The heater not getting hot indicates that water isnt getting there, but lets see the results of your hose temp test for that.
What could be happening is that the water pump is struggling to provide an adequate flow with the heater circuit in......but other things dont add up here.
One thing you can do:
actually disconnect the top heater hoses and put a garden hose down one and see that water runs through it....it could even have a giant air lock in it but this is rare in Holdens of this age. As best you can, run the water through and reconnect the hoses without letting the water drop out of the core. I typically do this by putting the garden hose in the top heater hose, take the cap of the radiator and fill till water comes out the radiator and the heater outlet on the top of the motor, put the cap back on and quickly connect the top heater hose.
Warning, dont try and pressure test using your garden hose, mains water can be at 100psi and this can blow out a heater core easily.
Being an sle you probably have air and there is a vacuum tap that controls the water flow to the heater. It should normally be open when no vacc is applied,(actually have the heater switched to on while you have the motor running, then turn the motor off, this will keep the tap open when you flush it) but testing whether this tap works would be one thing Id be looking at too.

[ezkii]

thanks, i will check all that, i quickly checked the hoses and they seemed to warm up, then i noticed a fuel leak in the hose to the carby and pulled the pin before it spilled onto the mainifold. will try again tomorrow when i have a new fuel hose on.

[Wrayza]

If your cooling system has recently been flushed out and was refilled with your heater core closed (temperature slider in car set to cold) then when you have opened your heater core (slider to heat) you have introduced a huge amount of air into the cooling system that was previously locked in the heater core.

The water naturally sits at the bottom of the water jacket with empty air space at the top (the cylinder head) which is where the dashboard temperature gauge usually lives. Hence the sudden temperature increase while the rest of the cooling system may seem fine.

I've done the exact same thing, however I'm not sure that it could happen as a cycle. Usually it will only happen once, then you'll have to top up the radiator.

[ezkii]

yeah, i checked the radiator, it seemed to have enought water in it no probs. i have noticed now after driving around for a while it is no longer overheating with the heater set to hot?????? but is still not heating tho.

very unusual, will keep at it though.

[benny999]

i have the same prob with my vh sle my heat doesn't go up just my heater doesn't get warm dono whats the deal