Glycol or Water?

[G-Pete]

Often here on this board we see posts of problems with the cooling management of the engine. Overheating engines or running “too cold” engines.
Shall we take a look at the cooling mediums?

A water solution of ethylene glycol/water has less specific heat capacity (SHC) than pure water. Now some numbers, in a 50/50 mix: At 36F the CHC is decreased by 20% and at 200F about 17%.

Propylene glycol, also many times used, has even a lower SHC. Now with the 3rd one here some numbers again: Let’s assume a cooling system with a flow of 100 gallon/minute. Pure water as a base line- ethylene glycol water mix would gain 20 degrees and propylene glycol would gain 33 degrees.

Ethylene and propylene glycols require less circulating mass for heat exchange, important for very small radiators. These glycols can absorb heat at higher temperatures without boiling. However, even with a lower vapor point water still carries more heat per unit.

There is a whole “team” working to keep the engine at the most efficient operating temperature. Let’s not overlook the pressure on the radiator cap. For every pound increased system pressure the boiling point goes up by 3 degrees.

Heat problems:
Most of the cars here have high quality aluminum radiators and (ask the manufacturer first) can be equipped with up to 20psi caps without problems. If you run straight water, make sure your car is not exposed to freezing conditions and add a corrosion inhibitor.

Low temp problems:
Start with propylene glycol and may cover a part of your radiator. Your goal for the Ford engines should be around 200F +/- (check with your engine supplier).