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#1
08-22-2004, 08:43 AM
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Mitsubishi diesel 4d56
Anybody here know anything about these things? I have one that keeps breaking rocker shafts at the cam cap 2nd closest to the fire wall. I pulled the head and can't see any evidence of piston/valve interation.
Any ideas? Thanks all.
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Andrew 300e 294,000mi 380sel 185,998mi 380se 309,980mi 
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#2
08-22-2004, 10:37 AM
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Is the valve itself siezed up in the guide?
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#3
08-22-2004, 06:43 PM
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A bit more info
Some things I neglected to mention.
It's the exhaust valve where the rocker shaft has broken on cylinder 4 (closest the fire wall). The engine ran for about 100km before it broke the shaft again. Also, there seemed to be air coming OUT of the air filter when the engine was running at idle. Is this significant? I don't know if the valve could be sticking intermittantly, is that possible? This is the second rocker shaft the motor has broken in about 500km. What is the most likely senario here? Stretched conrod? Sticking valve? Thank you Andrew
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Andrew 300e 294,000mi 380sel 185,998mi 380se 309,980mi
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#4
08-22-2004, 06:56 PM
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Posting on the tech help or diesel discussion would get you more answers. I don't have an answer except to say that air coming out of the intake seems to indicate a sticking or malfunctioning intake valve.
__________________
1977 300d 70k--sold 08 1985 300TD 185k+ 1984 307d 126k--sold 8/03 1985 409d 65k--sold 06 1984 300SD 315k--daughter's car 1979 300SD 122k--sold 2/11 1999 Fuso FG Expedition Camper 1993 GMC Sierra 6.5 TD 4x4 1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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#5
08-22-2004, 07:42 PM
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My Dad used to own an 88 Hyundai Excel. It had those jet valves that were used in the old carbeurated Mitsubishi engines for emissions purposes. His carboned up over time and stuck. They broke a couple of rocker arms when this happened.
What you are posting is definitely a problem with sticking valves. The head needs to be pulled and rebuilt. Exhaust valves can definitely build up carbon deposits from the soot in the exhaust. It sounds like this engine has been lugged, which would have caused alot of black smoke from unburned fuel. If this engine has an EGR system on it, then it would be entirely conceivable that some of this crud got caked on intakes as well. Regardless, you need a head job on that engine. It would be a good idea to inspect the piston tops as well for impact damage, since these valves are sticking. I am assuming at this juncture, that this engine has accumulated a fair amount of miles as well.
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