Cooling system modifications
The cooling system in the 3000M cars have always been marginal and was not properly planned from the beginning. Two type of radiators have been used, my car have the low wide type but later cars where equipped with a taller standing type. Any of these radiators are large enough to cool even tuned engines but there are other things that can be improved.
The radiator is located about 30 cm in front of the mechanical fan mounted on the engine and therefore this fan doesn't do much for moving the air. The original electric fan is small and not very effective.
Changed to a SAAB electric fan mounted in front of the radiator as the original one was worn out, this improved cooling somewhat but I still experienced overheating in city driving during hot days.
Mounted one more SAAB fan behind the radiator and removed the original mechanical fan. This improved cooling and I had no overheating problems.
I started to experience overheating problems again as I had changed the engine and the engine power was increased. I removed the two SAAB fans and mounted a large PACET fan in front of the radiator. This cured the overheating problems at low speed and city driving but I instead got overheating problems at high speed.
Added Redline water wetter and pure water to cooling system. This improved cooling a lot. Redline water wetter is a surface de-activant and breaks down the surface tension of water so heat transfer is improved, by using Redline water wetter with pure water the temperature can be reduced as much as 10 degrees.
Removed the large PACET fan in front of the radiator and mounted two smaller PACET fans behind the radiator, the theory is that air now can come freely into the radiator which should improve cooling at high speed.
Changed the pressure cap for a new one with higher release pressure, this minimise the risk of water boiling when the engine is shut off by maintaining a higher pressure in the system.
Changing the pressure cap and the fan setup somewhat improved cooling and no water loss at all but as I still had some problem with high speed overheating. My theory is that there is a problem with the bypass flow in the 3000M setup. Normally a small amount of water goes directly from the tap in the manifold just below the thermostat via the water heated auto-choke assembly and then back to the water pump. Normally this is important as there must be a way for water to flow through the engine even when the thermostat is not opened, otherwise there would be overpressure in the system and possibly the water pump would be destroyed.
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.
Normal and bypass type thermostat
The whole cooling system for the Essex engine works only according to the principle of least resistance, that is the water flows the way it meets that smallest resistance and as the bypass hose is quite small there should be a limited flow. However the cooling system in a 3000M is quite different from for instance a Ford Capri that use the same engine, the radiator hoses in the M setup is much longer and twisted which increases the flow resistance, (thereby reducing the amount of water that goes trough the radiator). Also in my case I have never used the original carb with auto choke so my bypass hose have been connected directly from the manifold to the water pump.
Now I have changed the thermostat to a special high flow 71 deg type from Robertshaw with integral bypass. I also have rerouted the hoses so all water now go through the radiator, (I have no bypass flow directly from the cylinder head to the water pump). This modification has improved the cooling very much, at idle the fans cut in not more than about 10% of the time and also cooling at high speed is vastly improved, it now seems that my cooling problems are finally solved. I can strongly recommend this solution for everyone that have a problem with cooling an Essex engine. I am using a modified Robertshaw thermostat with 160 deg F opening which should be good for any car that is used only at summer as mine, otherwise there are other temperature settings available also. I bought my thermostat from Stewarts components
There is also a lot of useful information about cooling systems on their web page.
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latest change on ... May, 2002