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Blasting out the debris
Page 97
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EVERY so often, a cooling system becomes clogged up in such a way that normal flushing techniques will not clear the passages out There are two alternatives left—a really potent blast through the system, or strip the engine down.
In one case, an engine began to show signs of clogging at the beginning Of the winter, but then proceeded to run quite satisfactorily until the spring, no doubt because of the rower ambient temperatures. But then, when the weather became warmer, the engine started to lose a lot of water, and it seemed clear that there were some internal blockages.
The condition of the thermostat, impeller and so on were checked to make sure that the cause really was in the coolant passages, and then the advice of a manufacturer of cleaning fluids was sought
Flushing gun
The company suggested that the strength of the solution be increased, and the engine operated for a longer period at 80 deg C. They recommended that afterwards, the system be flushed out with the aid of a water flushing gun —a nozzle with air and water Therefore, the radiator was blanked off to maintain the correct temperature, and the engine was run for 11/2 hours. Then, the system was flushed — but in two operations, first the radiator, and then the cylinder block and head. This approach s necessary to stop the thermostat closing and restricting flow, and in any case, some of the debris may get lodged in the system.
The radiator was attacked first, and to start with, the top and bottom hoses were disconnected from the engine. Then, the flushing gun was clamped with the nozzle in the bottom hose, and with the radiator cap sealed down, water was admitted to the radiator until the radiator was full.
Next, the water valve was closed, the air valve opened. and pressure was applied, enough to shift the water, but not enough to damage the hoses.
Once all the water had been ejected, • the radiator was refilled with water, and the process repeated until the water ejected was clear.
Before flushing the water jacket, it is advisable to remove the water pump, and replace it with a blanking plate, while the thermostat should also be removed. Then, the heater taps should be closed, and the flushing gun clamped so that the nozzle is in the water outlet passage, or if the thermostat housing has been removed, into the passage in the head. An important point here is that the nozzle should be at least as high as the highest part of the coolant passages in the head, and so it is preferable to replace the water outlet pipe.
The block is filled with water, the lower hose being temporarily blanked, and then the full air pressure applied to flush the water out — the lower hose being unblocked first.
Low pressure
Once the radiator has been flushed out successfully, it pays to flush through the heater matrix, unless you want complaints from the drivers when the weather is cold. in this case, though, it is important to remember that the heater matrix is relatively delicate, and so only low pressure should be used.
This is a fair lengthy procedure altogether, but is definitely shorter than a complete stop down, especially since a thorough flushing would be needed anyway. Fortunately, this sort of flushing is not often used, and then only on fairly old vehicles.