6.9L thump thump thump....

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Feb 14, 2011 | 09:26 AM

ibo

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6.9L thump thump thump....

hi guys! I've got an ol' 86 6.9l and the engine had started this new thump, thump sound. HAve not really fpound a pattern. It sorta comes and goes...some times it happens when it is cold then comes out of it...some times it only happens when it has been on the road for 20minutes. Not sure what the source is. any ideas gents?

Feb 14, 2011 | 10:32 AM

farmert

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From: western SD

My first guess would be valve guides worn, letting the valve not closing all the way when you get the thumping sound.

Feb 14, 2011 | 10:40 AM

polarismuddman

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From: Central, Florida

Could be a carbon issue.....have you run any fuel additives like Diesel Kleen lately?

Feb 14, 2011 | 12:24 PM

ibo

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thanks for the replies. have nto used any fuel additives. the truck spends a lot of time idling on the farm might that build up carbon? It also has to be started w/ starter fluid (ok fire away :-) I just got the truck and it had been sitting for a year. I was told the glow plugs burn out as soon as they put a new set it. I use the diesel safe starter fluid. could this be the cause? The way it comes and goes makes it sound like the valve guide idea might be the answer too.