ROAD AND WORKSHOP by Handyman
Page 57
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Solving an Overheating Problem
nUITE often in the rush and bustle of haulage repair activities, an overheating problem will be traced to the thermostat unit. This after a long period of service, will be found to have closed for thc last time. There is no real problem here—the answer is to fit a new one. However, there are occasions when the correct replacement is not readily available. Again there is no real problem— leave it out and work the vehicle until a replacement is to hand. This is quite a well known instruction and in most instances all is well. Yet one very important point can be missed. The pipeline between the thermostat housing and water pump is now permanently open. This line is known as the by-pass pipe and its use is controlled by the thermostat. If the thermostat unit is removed and no move made to close the-by-pass line, this line will provide an easy passage for water to circulate around pump and engine block—and the value of the radiator is reduced very considerably. So much so that the really hard-worked engine can begin to overheat and lose coolant rapidly via the overflow, although the lower section of the radiator can be quite cool. Nevertheless, the block temperature is now too high and unless noticed the final result can be partial or even total sei/ure and stoppage. All too often, the engine can be repaired and returned to service, the repairer being satisfied that the block and radiator are in order and that the pump is working. Although aware that the thermostat is removed, he can be unaware that the bypass line is still open.
There are various simple methods of blocking the by-pass pipe on removal of the thermostat. With the bolted flange type a thick blind joint is used with a good fringe left proud to indicate a tern
porary joint. Where the coupling is by hose-pipe, a simple plug can usually be found in the scrap box ready made, i.e. an old brake plunger or cam follower, either of which can usually be inserted into the hose and double clipped. kis also a good practice to put a dab of red paint on the hose. over the plug. This will draw attention to the blocked line on the replacement thermostat being eventually fitted. It should be remembered however that the thermostat plays a most important part in engine welfare and early replacement is recommended.