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Showing results for tags 'clean the fins on your onan'.
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Cause of death? Neglect by failure to clean grime off of cooling surfaces. I should post this in the engine section but anyone with a P Series ONAN needs to see this. I bought a 1990 416H with a bad ONAN engine a few years ago. I paid what the deck was worth for the whole thing including a new red vinyl wheel horse tractor cover. I finally got around to opening the engine to see what went wrong. The engine had about 1000 hours on it and the tractor was used primarily for mowing. The first thing I noticed was the extreme amount of grime around the cooling fins on the back and bottom of the engine. Clearly the engine overheated and the rod disintegrated. The cylinder wall was fine and the piston was still a snug fit in the cylinder. There was carbon but not enough to be the cause of the failure. I did not check the valve clearance on the back cylinder since it was clear the grime prevented the engine from cooling properly. The valves and valve seats looked fine. After seeing this I will be taking my ONANS off the tractors and giving them a thorough cleaning along with the de-carbon and valve clearance checks at least every 500 hours or so. This may be one of the main causes of the rear cylinder failures on our horses. The pictures of the engine are after a removed a significant amount of grime. Not sure what i will do with it but I did purchase a new rod and piston and new valves. Not sure how bad the crank is. The oil tube got destroyed also. If these engines are neglected and not allowed to cool properly they will be toast. Periodically cleaning the cooling fins on the entire engine is a must do. The way these engines are mounted in our tractors, it is way too easy to neglect the bottom and rear of the engine and it is not just grass accumulation. An oil temperature gauge may help provide a warning sign.
