I have a Cummins M11 in a Ford HN80 tipper that has developed a smoking problem. It has 800k km/500k miles on the clock and uses next to no oil. We use it mostly as a water truck with a slide in tank and towing a trailer with a tank as well, so a lot of low speed work ahead of a grader. The smoke is greyish in colour and only appears at low revs, usually worse after a period of idling, never at higher revs with a big load and never at startup, hot or cold. This week it has been hauling gravel with a trailer, so heavy loads over shortish distances, but smoking is neither better or worse. Initially I thought it might be a glazing issue but now Iam not so sure. Any thoughts appreciated. Cheers, Greg
Gray smoke sounds like unburned fuel, if it is, a overhead adjustment may polish it up. Most likely however a set of injectors are in order and a overhaul maybe.
Maybe the Turbo is carboning up and it needs to be Run hard for a couple hours. Our emergency generators have the same problem and running them with a load bank for a few hours cleans them up again.
Pulled the discharge pipe from the compressor side of the turbo and it was nicely coated with oil, so looks like that is our culprit. New turbo on the way.
I thought I would post an update on this motor... Might help someone else one day. We replaced the turbo with a reman Cummins unit and had the aftercooler cleaned. All was well for a couple of weeks, until it started smoking again, eventually becoming worse than ever. Again, we checked the all the usual suspects of smoke producing problems. Long story short, someone suggested that the air compressor might be leaking into the crankcase. Sure enough, with engine idling and normal amount of blow by at the breather, when the filler cap was removed there was an audible hiss, indicating excessive crankcase pressure. Removed compressor output line and tried again.. still had excessive pressure. Removed valve cover to find that this engine has a metal wool type pad filtering the breather output which was coated with enough oily residue to restrict the air flow at certain rpms. Cleaned the pad and gave it an overhead set while we were there and it has been fine since. In the end, a simple fix to an annoying problem.
Thank you for the update.. Nice find.. I'll bet that turbo was a chuck of change?? along w/ an after cooler cleaning.. Just think how much it would have cost you if a set of injectors was included.. OUCH..