TM 55-1930-209-14&P-19 Table 9-3. Preventive Maintenance Checks and Services for Electrical Power Systems (Continued) B-Before D-During A-After D-Daily H-Hourly Interval INTERVAL ITEM PROCEDURES EQUIPMENT ITEM TO BE CHECK FOR AND HAVE IS NOT READY/ NO. INSPECTED REPAIRED OR ADJUSTED AVAILABLE IF B   D   A   D H AS NECESSARY 3) The heat exchanger and coolers should be serviced every season. Depending on operating conditions, this period may have to be reduced. Normal operating temperatures will vary slightly from engine to engine because of design tolerances, installa- tion, and hull variations.  Once the nor- mal operating temperature has been establihsed for a particular engine, any excessive rise in temperature should be considered abnormal and immediately investigated.  If a cooling system problem is suspected (or com- firmed) the following guidelines will provide a means for isolating the cause. WARNING The coolant in an operating or recently stopped engine is very hot and under pres- sure.  If the filter 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. (a) Check the coolant level in the header tank and ensure the proper pressure cap is being used. (b) Check the sea cock and strainer for obstructions; clean where nec- essary. (c) Check the seawater pump Seawater pump impeller.  Replace if damaged. impeller damaged. Ensure that no pieces of the impeller (if broken) have passed into the connecting pipes (i.e., inlet and outlet) to restrict water flow. (d) Check heat exchanger for obstructions within the cooling core tubes on the seawater side. Once the end cap and/or plates are removed, any scaling within the core tubes can be removed by passing a rod (slightly smaller than the internal bore) thru the tubes. Do not use excessive force when pushing the rod thru the tubes. 9-44