Core plugs, which fill holes left in the cylinder block when it is being cast, are other likely sources of leaks. They may be blown loose by pressure from the system, corroded, or even loosened by vibration.
Use a mirror and torch to find if there is one hidden behind the engine, made inaccessible by the bulkhead.
If a thorough search fails to locate the leak, suspect a damaged gasket between the cylinder head and the cylinder block, or a cracked head or block.
If the cooling system springs a small leak when you are on the road, you may be able to drive home slowly by releasing the radiator cap to its first catch, or by putting a match under the
of the cap to
the pressure. Watch the temperature gauge; if it goes into the danger area, stop and allow the engine to cool.
If you suspect an internal coolant leak, allow the radiator to cool, take off the cap, and look for signs of oil or frothy bubbles in the radiator or
With the engine running, smell the coolant itself - if there is a whiff of exhaust
, the cylinder-head gasket may be leaking. To make certain this is the cause, before removing the cylinder head (See
How to remove a cylinder head
) to investigate, have a garage test the cooling system pressure.
Any movement means that there is wear in the bearings. This will lead eventually to rupture of the water
shaft, and a leak will occur. Look also for leaks around the pump
, tightening the flange bolts or replacing the gasket may stop the leak. If the fan is not mounted on the water-pump pulley, rock the pulley instead.
A worn or leaking water pump must be replaced - it is false economy to have it repaired.
Another sign of wear is noise, but a screech when starting from cold or accelerating quickly may also be caused by the belt,
bearings or a power-
The most frequent cause of water pump failure is a loose, slipping, worn or damaged drive belt. This usually leads to overheating, a reduced charging rate - and eventually a broken belt.
The belt usually drives the generator, as well as the pump, and the tension on it is critical: too slack and it cannot turn the generator and water pump; too tight and it may damage the bearings of both.
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