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.