Overheating Radiator

[willo]

You are welcome to disagree. But I'm still right!

I've studied thermodynamics and have many examples in domestic and racing practice where I've seen this to be true.

These are two examples:
 
I own a 1930's vintage car. Cooling system is perfect except it runs hot all the time and I cant get the correct thermostat for it. I removed the thermostat and it over heated again but only on highway driving. I made a metal disc with a 25mm hole in it and placed it where the thermostat should be as a starting point to give me some idea if I needed more or less flow. Of course it was slow to warm up without a thermostat but amazingly, it does not overheat and sits right around where it is supposed to be. I have left the disc in place with no dramas since.

I have been crewing for a V8 speedway team for a number of years. We decided to change the power steering set up, in doing this we had to change the pulley sizes and therefore ratios. First heat out we had overheating problems. Realising the coolant was flowing a lot faster because the waterpump was now spinning a lot faster too.  With no way to change the pulleys, we changed out final drive ratios (thank God for quick change diffs) reducing the engine RPM (and sacrificing HP) and the car finished the night OK. Back in the workshop, we re-did the pulley set up bringing the waterpump speed back nearer original and have had no issues since. You must appreciate that these race engines are working harder than normal and cooling is marginal at the best of times. So it appears Beddy cooling systems are not so different.

Anyway, again, for what it is worth.

Beerbeddy

Yep, I agree with what you are saying.
the issue with removing the thermostat is that the water moves much faster and much sooner as the engine warms up of a morning but importantly, it goes quickly around the front of the motor only and the back of the motor has minimal circulation. thus, the back of the motor will run hotter and lead to overheating.
Similarly with the pulley ratios.  it pushes all the water around the front of the motor at a faster rate and not letting the air flow through the radiator do its work. 
It really comes back to the interaction between the water flowing at the right volume aka thermostat/restrictor in place with no blockages and correct water pump ratio and the airflow through the radiator aka no blockages and the radiator surface area is sufficient to cool the volume of water passing through it. 
It is a science and it all has to work together in unison.

Cheers

Neil

[Sammy]

yes but are your issues a result of too fast flowing water or especially in the case of the speedway car the pump is spinning too fast and cavitating in the water rather than moving it!

thats the biggest reason for alot of underdriven balancers for new motors these days, to slow everything down so when they are racing always at high RPMs the water and power steer pumps arn't spinning too fast!

obviously there is a point where too fast or too slow are a problem, and finding the happy medium is the key, ie. electric water pumps.