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Author Topic: Blue smoke on start up  (Read 3633 times)
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87' MCI 102A3 - getting there...


« on: June 11, 2006, 09:07:55 PM »

My bus has some blue smoke on start up and while under heavy load.  What causes this and what can be done to fix this?

Thanks - as always...


I have heard it said, "life comes at you fast".  I didn't know it would be in the shape of a bus  :-)
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« Reply #1 on: June 11, 2006, 09:16:05 PM »

Blacke smoke = to much fuel for the air supply.  White smoke = fuel not firing off at all-like on a cold morning before and right after a cold engine starts (should disappear within about 5 minutes).  Blue smoke = oil burning-from worn or broken rings; worn valve seats; leaking blower seals, etc.  Usually blue smoke means the engine is worn out, even though it is still running.  Now is the time to overhaul the engine before it does blowup and cost you big time money to repair.  Now you could maybe get away with rings, bearings and valve job.  Good Luck, TomC

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

« Reply #2 on: June 12, 2006, 03:51:24 AM »

Danny, you stated "Some blue smoke".  I can't help but feel that it's oil consumption.  If it was only startup I'd point to intake valve guides.  I haven't looked at the book but when I went to DD school they didn't use intake valve seals like they do on automitive applications...they might now.  Then the only solution was to either replace the valve guides or Knurlize them (much simpler fix) but of course the heads must come off and be disassembled.

How much oil does your engine use during a full day run?  That might point out how much wear there is.  A compression or a leak down test will tell you about the condition of the pistons and rings.

In the Marine application we expected Detroits to use a quart a day...even new engines.  But bear in mind that they're running hard and uphill all day.  Some guys let 'em run that one quart low however I didn't.

Your engine might just be approaching the point where it's getting tired and you can guess what's ahead.

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