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msinclair 09-13-2009 10:14 AM

Yanmar diesel ran without water cooling
My 1975 Tanzer 26 has a Yanmar YSE 8 which was run about 1 hour without the water intake being connected in June 2009. The water impeller was replaced as was the burnt out exhaust pipe. The engine appears to run well except a small leak from the water pump. Should I be concerned about other damage to the engine? Should it be disassembled? What damage should we look for?
Mike Sinclair

sawingknots 09-13-2009 11:55 AM

i did the same thing with my ysb 12 about 2 years ago,i've not saw any damage,i would just continue to run it and maybe keep an eye out for water in the oil[blown head gasket]if you see no damage after about 4 hours running i'd say its fine

WanderingStar 09-13-2009 12:10 PM

My sb12 used to burn up head gaskets. The cooling passages were clogged. But it kept running fine when hot, though I don't like to motor far anyway.

roline 09-13-2009 03:50 PM

Running an engine without coolant forces the oil to act as a coolant as well as lube. It can not transfer the heat as well as water. Areas that will take the brunt would be the cylinder bores if the pistons thermally expand and score the cylinder walls and the excessive heat can take the temper out of the piston rings. Also in the head the excessive heat can cause the valves to expand in the guides and score. Valve stem seals also can be pre-maturely aged and may start to leak. A sever over temp will age the oil and give it a funky smell.
Damage would be noticed by hard starting, low compression or by white exhaust indicating burning oil. ( oil level change also)
Extreme over temps will also affect gaskets and bearings and warp heads. We had a small block chevy on an engine dyno running a thermal shock test run at WOT without coolant due to a dyno controller dying. The engine was stopped when this was detected. The oil stunk but the engine still started and ran when the oil was changed out after it was allowed to cool.

RichH 09-13-2009 06:32 PM

Be sure to re-torque the cylinder head as if high temperature soaked the head area the engine bolts may have permanently elongated due to the extreme temp. Otherwise, just keep an eye on the engine - including 'profiling' the engine with an infra-red thermometer (record temps vs. various areas of the engine) to be able to 'see' if/where thermal problems are developing (good idea for any engine).

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