Disclaimer!
The opinions expressed here are entirely my own, so please use any advice on your own risk!


About cooling systems


There seem to be a lot of misconceptions about cooling systems, having a car myself with known cooling problems have made me study this area in some detail and I have collected some useful information here.

Description of a standard car cooling system

Normal water flow
Normal water flow

The water pump has 2 functions, circulating water trough the system and keep the operating pressure. From the water pump the water is normally pumped into the lower part of the cylinder water jackets. From the water jackets the water flow trough metering holes in the head gaskets to the cylinder heads. From the cylinder heads the water goes via the thermostat, (if it is open) to the upper radiator inlet. The water is cooled in the radiator by the airflow and the cooled water goes from the lower radiator outlet to the water pump. if the thermostat is not open, (before the engine has reached operating temperature) the water does not normally go trough the radiator but instead trough the bypass flow, (in the normal Essex setup this is from the pipe in the manifold located below the thermostat housing, trough the carb termochoke and to the water pump).

The bypass have two functions, to make the engine reach operating temperature as quick as possible even in cold weather and to act as a relief for the pressure built up by the water pump, without any bypass or other possibility for water to flow out of the engine there is a possibility to cause damage to the water pump.

BUT! the bypass have only negative effect on the efficiency of the cooling system, one simple way of improving cooling is by removing the bypass flow, necessary pressure relief can be achieved by some holes drilled in the thermostat.

Function of the thermostat

The thermostat have 2 functions, keeping the temperature constant and controlling the pressure in the cooling system. It is important to try to keep the temperature on the right level as the engine wears more with too low or too high temperature and also the fuel efficiency is affected. It is wrong to remove the thermostat in order to improve cooling, this will lower the pressure inside the engine and can lead to localised boiling usually somewhere in the cylinder heads. In racing engines where sometimes the thermostat is removed it is replaced with a restrictor plate in order to control the pressure.

In some engines a bypass thermostat is used that blocks off the bypass passage when the thermostat opens but this type is not used in the Essex engine.

Bypass and normal thermostat
Normal and bypass type thermostat

How to generally improve cooling in an engine cooling system

Cooling in car engines can be improved by:

Increasing the flow of cooling liquid

Increasing airflow trough the radiator

Improving heat transfer from metal to cooling liquid

Increasing the size of the radiator


Increasing the flow of cooling liquid trough the radiator always improve cooling. It is a common misconception that if the liquid flow trough the radiator is increased cooling will suffer as the flow is too fast for it to give up its heat. This is completely wrong, cooling in a car cooling system will always be improved if the flow of liquid trough the radiator is increased, this is common knowledge valid for any system involving heat exchangers.

The only time when cooling can be decreased at increased liquid flow is when the flow will be too turbulent but this doesn't happen in an ordinary car engine.

Methods of improving flow can be by changing the water pump to one with increased flow, or to reduce the diameter of the pump pulley in order too increase the pump speed. I have improved the flow in my car in a very simple way by removing the bypass flow completely and also by using a special high flow thermostat, (now all water flow trough the radiator ).

Increasing the airflow trough the radiator installing efficient electric fans and blocking off air passages outside the radiator also improves cooling, (as much air as possible should go trough the radiator). The mechanical fan in the TVR 3000M and also other cars are usually very inefficient and draw a lot of power from the engine. Blower fans installed in front of the radiator block off the flow of air and will therefore have to work more than suction type. I have installed 2 Pacet PF0810 fans behind the radiator, each fan flow 540 CFM. This arrangement is similar to the one used in newer TVR's that also use 2 fans.


Installed fans in my car

Improving heat transfer from metal to cooling liquid. Pure water has twice the heat transfer capability when compared to 50% glycol antifreeze/coolant in water, therefore cooling can be improved by reducing the amount of glycol antifreeze used. By reducing surface tension of the cooling liquid cooling can be even Further improved. Heat will transfer easier both from the engine to the cooling liquid and from the liquid to the radiator. I have tried Redline water wetter with positive results.

Increasing the radiator size is always a sure way too increase cooling but it is often not necessary. I know that many people with M cars have changed the radiator either to a larger one from another car or even have installed racing radiators. I believe there is nothing wrong with the standard radiators used in the M cars, they are big enough even for highly tuned cars but there are other easier and cheaper ways to fix things that lead to cooling problems.

Summary, for improved cooling:

Maximise cooling flow by removing or reducing bypass flow and if possible by changing to a higher flow water pump.

Increase airflow trough the radiator by blocking off air leaking beside it and by installing effective "suction" type fans behind the radiator.

Improve heat transfer by reducing or entirely removing glycol antifreeze from the cooling liquid, add a surface de-activant as Redline water wetter.

Only if everything else fail, change to a bigger radiator.


Changing the electric fans together with a new thermostat and modifying the bypass flow take care of all cooling problems in my tuned M car and doesn't cost very much, (much less than a purpose built racing radiator). As a bonus the car looks original and there is no need to modify any radiator mountings.

About the cooling system in my TVR
Cooling system modifications

Back to My TVR


Created on ... May 24, 2002,
modified on... June 30, 2002