Mitsubishi Valves


Old 11-12-04, 02:28 PM
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Join Date: Apr 2003
Location: Ohio
Posts: 1,376
Mitsubishi Valves

I have two 25 hp Mitsubishi diesel engines with approx 1800 hours on them that both had valve failures at the same time. By failure, I mean that when we took them out of the engine, we found that the exhaust valve on the number one cylinder on one of them looked as though someone had taken a punch to one small (1/4"") area on the top of the valve and hit it, knocking pieces down into the cylinder and basically ruining the engine. The other one had the same chunk punched out of the number three cylinder, ruining that engine also. We are trying to find out just what caused these valves to destroy themselves, and the engines like this. We have ruled out bad fuel, or gas in the diesel tank,as there was no damage to any of the other valves or cylinders in any of the engines, and all the other engines that are fed from the same fuel tank are in fine shape. The valve adjustment was within specs. I will take a digital photo of these tomorrow, if someone thinks they can help. Any comments on your experiences would be helpful!
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Old 11-13-04, 01:09 AM
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Join Date: Jul 2001
Location: USA
Posts: 16,814
The engine is probably lugging under too much of a load. Carbon will build up in this situation from the governor feeding it so much fuel to meet the load's demand. The carbon creates a hot spot, and the valve deteriorates from there. If the engine can be throttled up some, or the load decreased some, I would reccomend doing it to prevent the problem in the future. If the engine is already at full throttle, and the load cannot be reduced, then you need a bigger engine. What kind of equipment is this bolted to?

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