Heat Exchangers, Oil Coolers and Air Charge Coolers
A heat exchanger usually consists of a casing with a core (tube stack), which is the actual heat exchanger. The oil cooler
usually has a smaller core and is sometimes an integral part of the engine heat exchanger.
The heat exchanger and coolers should be serviced every season. However, it is stressed that, depending on operating
conditions, this period may have to be reduced. Although the coolant temperatures of new engines cease to fluctuate
after a short period of operation, the stabilized (normal operating) temperatures will vary slightly from engine to engine
because of design tolerances, installation and hull variations. once the normal operating temperature has been
established for a particular engine, any excessive rise in temperature should be considered abnormal and immediately
investigated. If a cooling system problem is suspected (or confirmed) the following guidelines will provide a means for
isolating the cause.
1.
Check the coolant level in the header tank and ensure the proper pressure cap is being
used (7 psi or .492 kgf/cm2). The coolant in an operating or recently stopped engine is very hot
and under pressure. If the filler pressure cap is suddenly removed the liquid may spurt and
cause injury by scalding. Always stop an engine and allow it to cool before removing the cap.
Once cool, loosen the cap slowly to relieve the pressure.
2.
Check the sea cock and strainer for obstructions - clean where necessary.
3.
Check the sea water pump impeller-renew if damaged. Ensure that no pieces of the impeller (if broken) have
passed into the connecting pipes (i.e., inlet and outlet) because, if so, they could restrict water flow.
4.
Check all heat exchangers (coolers) for obstructions within the cooling core tubes on the sea water side. Once the
end cap and/or plates are removed, any minute scaling within the core tubes can be removed by passing a rod
(slightly smaller than the internal bore) through the tubes. Do not use excessive force when pushing the rod
through the tubes.
If the tubes are so clogged that a rod can not be passed through them, the core will have to be removed from its
casing and boiled in a caustic soda solution. Commercial cooling system cleaners can be used for this purpose,
providing they are recognized as being acceptable by the heat exchanger manufacturer. Reassemble with new
gaskets, seals and "O" rings.
If a reduced power and/or excessive smoke condition exists in addition to an Increase in coolant temperature with a
turbo charged engine having an air charge cooler (Inter cooler), check the inter cooler and, if necessary, clean as
described for heat exchangers.
5.
Check - especially if the engine was operated in muddy or silty water- the exhaust manifold outlet elbows and the
exhaust water injection connections for mud or silt restrictions.
6.
Oil Coolers - both engine and gear box - can also effect engine coolant temperatures. Oil coolers should be
checked and cleaned as described for heat exchangers.
7.
It is particulary important for TV8.510 marine engines to check the last cooler in the sea water system - usually the
gear box oil cooler - for water flow restrictions. This cooler should be checked any time there is suspicion of a
higher than normal temperature and, in addition, it should be checked at least yearly with seasonal weekend
cruising and twice yearly with extended cruises.
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