Foothills Antique
Tractor and Engine Club

Many engines used in old tractors, cars, trucks and stationary equipment use the thermosiphon cooling system.  This eliminated the need for the water pump, and prevented the possibility of water pump failure.  Since heated water rises, the water in the engine cooling jacket will flow upward through a water pipe to the top of the radiator.  Cooler water from the bottom of the radiator enters the bottom of the engine, setting up a constant flow of cooling water.

There is no thermostat, so engine temperature is regulated by controlling air flow through the radiator by raising or lowering a cloth curtain in front of the radiator, or by adjusting mechanical shutters.  The shutters are preferred since the operator can adjust them without stopping the tractor.  A curtain requires walking up front to roll the curtain up or down.

The main disadvantage of unpressurized thermosiphon cooling systems is overheating.  Since recommended operating temperature is 190F, and water boils at 212F, boilover was not uncommon.  Boilover is prevented by regulating airflow through the radiator and using a proper antifreeze/coolant mixture to raise the boiling point to about 230F.
 

FORCED CIRCULATION:

As tractors became more powerful, natural circulation was not able to remove the engine heat fast enough.  Forced circulation by a water pump can remove engine heat more efficiently, so engines can be made more powerful without extremely large cooling systems.  Modern cooling systems use antifreeze/coolant and pressurization to raise the boiling point to over 250F.

If your tractor tends to overheat and boil over, check these items:
 

• the radiator is filled with a 50/50 mixture of water and antifreeze/coolant
• the radiator cap is for the proper pressure (16 psi is common today); an old cap may be weak and not maintain proper pressure
• the radiator is not clogged internally with mineral deposits and debris and externally with dust and debris
• the fan belt is properly tensioned
• the engine is not lugging at low rpm (the fan cannot draw in enough air and the coolant pump cannot circulate the coolant fast enough to cool the engine)

A neglected cooling system can result in costly repairs.  Also, the downtime will probably occur when you need the machine most or when you are farthest from help.  This also results in costly loss of productivity.

The following basic preventive maintenance steps can minimize your chances of downtime:
 

• keep the grille and radiator clean and free of debris and dust accumulations that can reduce airflow; blow or wash the debris away from the rear of the radiator.
• flush the cooling system and replace the coolant at the recommended intervals (read the label on your antifreeze jugs); common intervals are 24 months/24,000 miles up to 60 months/150,000 miles
• use distilled water for the final flush and when filling the radiator to reduce mineral deposits in the radiator (at 60 cents per gallon, you can final flush and fill the radiator with less than 5 dollars worth of distilled water - a cheap investment that can prolong the life of a 400 dollar radiator)
• check the condition of clamps, hoses and belts at least monthly and replace any that are cracked or have bulges
• replace all the water hoses and belts at least every 4 years or at the mileage/hour intervals recommended by the manufacturer
• check the condition of the water pump monthly; relieve tension on the fan belt and check the condition of the bearing; also check for leaks and see that the weep hole on the water pump monthly is open

• Prestone
• RadiatorInfo
• Fleetguard

Safe Brands Corporation