Cooling issues

[aussiejohn]

G'day mates,
Just joined this Forum, seems to be plenty of knowledge here. I have a VH 253 originally but now has a "warm" 308. Just a cam and a full balance. I fitted a twin electric fan set-up from a Falcon and it works well, but the car runs way too hot on a hot day. Temp is fine in cooler months, but on a hot day, the temp gauge keeps climbing.

Of course, you need the AC on a hot day and this just makes it worse. The motor starts pinking when the temp gauge hits the red area, and I have to turn the engine off and let it cool down before I break something.

Anyone else have this problem??? If so, what did yiou do? The car has a three row radiator, but I'm thinking of a later model aluminum radiator out of a VT or similar.

I have to fix this problem, I don't want to kill the engine. It's a weekend car, I have a DD for work, but I want a reliable car that I can drive on a hot day.

Over to you.

Regards

aussiejohn

[DANNY8]

I have the exact same problem with my mild 253. I don't know why it's overheating as the radiator was fine with the last motor, and I've used new radiator hoses and a new thermostat. Surely can't be a blockage in the motor as it was acid bathed b4 it was put 2gether and it's only been running for a few weeks.

Altho I wouldn't suggest turning the motor off when the temp gauge is in the red. Mines got up there a few times, so I pull over and spray water all over the front of the radiator. I keep a fair few bottles of water on hand. Then the temp normally goes down so I switch the motor off then fill her up with water.....it seems to drop a lot out of the overflow bottle....dunno why.

Wat would cause the cooling system to spew all the water out of the overflow tube?

[aussiejohn]

Danny,
Thanks for the reply. I got the rad back from my friend Leigh, who runs one of the biggest radiator repair companies in Melbourne. He said that it wasn't blocked and that the problem is lack of airflow.

Seems the GMH engineers knew what they were doing back in the 80's with the big belt driven fan. The twin electric fans are just not pulling enough air through the rad. at suburban speeds ( 30-60 kph) so the engine just gets hotter. He said a good test is to run the car (idling) with the AC on on a hot day and when the temp gauge heads north, squirt the rad. with the hose. If the temp gauge drops, then the air flow through the core is insufficient to keep the temp constant.

There are three solutions: (1) buy an aluminum radiator and twin fan set up out of a late model V8 Holden/Falcon, but that's around $800.
(2) put the original belt driven fan back on and put up with the noise and slightly higher fuel consumption, and (3) fit bigger electric fans ($$$) and that might do the job.

So tomorrow, the original fan will go on and I will take it for a drive with the AC on and see what happens. If it keeps the temp constant, I'll probably leave it for a while, but I'd still like to experiment with bigger or more powerful electric fans.

The only other thing is the radiator mounted temp. switch that turns the fans on and off. I'll get one with lower settings. The current one is 95/100 and that seems a bit high. 85/90 should be better.

I'll report my findings.

Cheers

aussiejohn

[DANNY8]

I don't have aircon and I got rid of the thermo on the last motor, been running a clutch fan for a few months. I guess I'll figure it out eventually.....sumfin can't be right lol.

[commsirac]

Danny,

Seems the GMH engineers knew what they were doing back in the 80's with the big belt driven fan. The twin electric fans are just not pulling enough air through the rad. at suburban speeds ( 30-60 kph) so the engine just gets hotter.

It pays to never second guess the people that designed your car!
Cars that come with electric fans have been designed for them. The major obstacle is to make sure the aerodynamics allow enough air through the thing at speed. Whilst some think it will be pouring in at 100km/h without a fan, the way the air flows under the car can create a big difference to the amount of air getting through the radiator....as it has to exit under the car and can cause the car to overheat at speed if the original engine fan isnt used when the motor is working hard.

Danny,

He said a good test is to run the car (idling) with the AC on on a hot day and when the temp gauge heads north, squirt the rad. with the hose. If the temp gauge drops, then the air flow through the core is insufficient to keep the temp constant.

Well basically that will tell you the only way to improve cooling with the existing radiator is to improve the airflow, but it doesnt mean the airflow is too low....it could mean the radiator itself isnt functioning properly.

Danny,
put the original belt driven fan back on and put up with the noise and slightly higher fuel consumption, and (3) fit bigger electric fans ($$$) and that might do the job.

is your original fan a thermatic clutch fan, they move a lot more air....and only when you need them too. Generally once they are warmed up they will not create additional noise. They will not create extra fuel consumption, just a myth that makers of aftermarket electric fans have peddled.. A fixed fan can use a little more fuel in high rpm circumstances and add to noise.

Danny,
If it keeps the temp constant, I'll probably leave it for a while, but I'd still like to experiment with bigger or more powerful electric fans.

Even if you doubled the power on the au fans they still wouldnt match what the standard holden 7 blade clutch fan is capable of at 2500rpm, If you need to run electric fans at cruise in any temp, there is no point to having them. You'll be burning extra fuel through the inefficient process of having the alternator loaded up providing the extra electrical energy.
Having to run them on the highway constantly in 40 deg heat to try and cool the motor will see them fail within a relatively short time. The basic idea to running electric fans the idea is that they should only come on in low flow air conditions, at speeds less than 40km/h. They should not come on at any temp(even 45C) if you are cruising at >40km/h, the combination of radiator and ram airflow needs to be able to provide enough cooling without fans.

Is your problem only at cruise, or at idle as well? basically the au fans put out a similar amount to the clutch fan at idle and obviously replacing the electric with mechanical at idle may not fix that problem. Holden did equip aircon cars with auxilary electric fans along with the clutch fan to keep them cool enough at idle with the ac on.

[Dayvo]

I have the exact same problem with my mild 253. I don't know why it's overheating as the radiator was fine with the last motor, and I've used new radiator hoses and a new thermostat. Surely can't be a blockage in the motor as it was acid bathed b4 it was put 2gether and it's only been running for a few weeks.

Altho I wouldn't suggest turning the motor off when the temp gauge is in the red. Mines got up there a few times, so I pull over and spray water all over the front of the radiator. I keep a fair few bottles of water on hand. Then the temp normally goes down so I switch the motor off then fill her up with water.....it seems to drop a lot out of the overflow bottle....dunno why.

Wat would cause the cooling system to spew all the water out of the overflow tube?

Just a thought , Did you rebuild the motor? i know of a few guys who have rebuilt their motors and put the gaskets that goes between the inlet manifold
and the head around the wrong way which blocks off the water jacket and causes overheating

[DANNY8]

Just a thought , Did you rebuild the motor? i know of a few guys who have rebuilt their motors and put the gaskets that goes between the inlet manifold
and the head around the wrong way which blocks off the water jacket and causes overheating

I've heard of that happening, but nah I didn't rebuild it. A mate did who pretty much does it for a living, so I'd assume they are on the right way.

[VR38]

Check you have a spring in the bottom hose and have the radiator cap checked if it is seating properly if you are loosing water thru it.

[gsxrdan]

After changing every conceivable item associated with cooling in one of my cars (loosing water thru overflow) i finally realised that regardless of if it was really hot, there still wasn't much air flowing thru the engine bay - went to a wreckers and got a new clutch fan and hey presto it didn't cook anymore! i know it wont help you much aussiejohn, but might help danny8. id rather a clutch fan (that works) than belt driven (but happy the VR has a lectric fan)

[leigh 7005]

make sure you have a thermostat coz if you dont have one water circylates to quick and dosent cool in the radiator and with the thermo fans it might be a stupid answer but make sure they are pulling air not pushing air

[commsirac]

make sure you have a thermostat coz if you dont have one water circylates to quick and dosent cool in the radiator and with the thermo fans it might be a stupid answer but make sure they are pulling air not pushing air

Yes and no: yes make sure you have a thermostat so the engine runs at the right temp, and no, cooling is increased with higher flow through the radiator, the thermostat reduces cooling by slowing the flow through the radiator.

[Cane_It]

Yes and no: yes make sure you have a thermostat so the engine runs at the right temp, and no, cooling is increased with higher flow through the radiator, the thermostat reduces cooling by slowing the flow through the radiator.

bullshit, the restriction of the thermostat does 2 things,
applies back pressure to the cooling system to minimise air pockets
slows the coolant flow so that the coolant spends enough time in the radiator for heat transfer to occur...

[commsirac]

bullshit, the restriction of the thermostat does 2 things,
applies back pressure to the cooling system to minimise air pockets
slows the coolant flow so that the coolant spends enough time in the radiator for heat transfer to occur...

Disagree.
I wont go into too much detail about the "coolant going to fast through the radiator to cool down myth", but perhaps look at the myth from the other direction and you will see how ridiculous it is:

if the coolant is going too fast/not in the radiator long enough to cool down, then likewise it isnt in the engine block long enough to heat up either. If the was any basis to the myth we could speed the water pump right up and the coolant wouldnt be able to accept or reject any heat. The heat would stay in the motor(eventually glow red hot) and the temperature gauge would read low due to the coolant moving too fast to accept any heat from the block.......silly heh!

Again, the faster the coolant moves the more heat rejected by the radiator(its all about Newton's law of cooling), though it does reach the point of diminishing returns at about 80L/minute for a v8 at full noise.
Engineers design the cooling system so the water pump has enough flow with the thermostat restriction in place. Hence removing the thermostat is not going to improve cooling to any measurable degree.

[VR38]

Agree with commsirac on this one.

What he said about the water speed is also true and to add that the greater the speed the greater the scrubbing effect the radiator has on the heat in the water.

Also there is no such thing as back pressure minimising air pockets, this is why a, the header tank or bleed nipple is the highest point, and b, working in conjunction with the pressure cap and the expansion tank keep air pockets to a minimum.

If anything, back pressure on a water pump (especially those older motors like the 202 and the 308 where the bypass has been deleted) will create cavitation.

[aussiejohn]

Thanks for all the replies guys, especially commsirac, you seem to know what you're talking about. I put the original thermo-clutch fan and shroud back on, and the same thing happened. It ran hot and when I shut it off after a trip 'round the block, it bubbled into the overflow tank for several minutes.

I also replaced the convoluted fuel line with the electric thingy in it with a one piece line I bent up myself. Now I've got a fuel leak at the pump, so I can't drive it until I fix that.

I think that the 45 degree heat last week in Melbourne didn't help, so I'll try again once the fuel line doesn't leak.

The thermostat is pretty new and I'm sure it works right; the rad. cap is almost new and the water pump is several years old, but hasn't had many miles put on it in the last decade.

I'll keep plugging away and let you know the outcome, but a big aluminum radiator is sure looking good.

Regards from Bayside

aussiejohn

[VR38]

Does it pink/ping at around half throttle?
I had a similar problem I was chasing on a gemini and it was only after the head gasket went that I found there was way too much shaved off the head combined with oil consumption thru the valve guides causing the problem.
New head and it is a totally different car.
Other cause maybe a blocked radiator.