An old topic I know but I have a problem with my
Volvo Penta 2003 indirectly cooled
engine. Towards the end of last year I attempted to change the
coolant. On removing the drain
plug I found that it was bone dry. Having read the considerable correspondence on the topic in Cruisers Forum I first checked that the space inside the drain
plug was clear. (I can insert a flexible curtain rail a full 8 cm into the block)
Subsequently I have flushed the
water jacket with both Rydlime and various other radiator
flushing compounds without success. When I run the
engine I am able to measure the temperature of the
water jacket using an infra-red temperature
sensor. The top of the block at different places varies from 68 deg C to 74 deg C (top of the thermostat housing). The bottom of the block around the area of the engine sump is about 78 deg C.
I am able to drain the
coolant by disconnecting the pipe that goes from the internal
water pump to the
calorifier. The drained coolant is about 5 ¼ litres. The coolant is a light brown colour and contains particle of light brown sediment. These particles can be dissolved in a solution of oxalic acid so I presume that they are largely made of iron.
Based on this information I should like to know if it is safe to use the engine for extended periods (eg for at least 4 hours). Secondly is it possible to remove the blockage to the drain plug using either oxalic acid or some other acid? If so please advise on a suitable acid and recommend its concentration. Any other alternative suggestions would also be much appreciated.