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Author Topic: Troubling smoke after idling  (Read 1034 times)
RickB
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81 MCI 9 smooth side 8V71 Allison 754




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« on: December 01, 2012, 04:21:51 PM »

I have some pretty bothersome blue smoke after starting and waiting for the bus to air up it lasts for about a mile down the road and then completely clears up. The bus starts unbelievably well so I don't think it's a worn out engine. Thinking its either blower seals or a cracked oil ring. Leaning towards the blower seals as the oil in my slobber tubes is pretty equal on both sides of the motor and yes I use straight 40 weight oil . Plan to use a scope to get a look at the vanes in the blower next week. Bus is running great, did 65 to 70 for four hours today and will do the same tomorrow. 50 to 55 lbs of oil pressure at 65 mph, running cool, everything normal except for excessive oil out of the slobber tubes and the momentary blue smoke. This has been a gradual change over the last couple years. Any thoughts?
Thanks,
Rick
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I will drive my Detroit hard... I will drive my Detroit hard.
lostagain
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« Reply #1 on: December 01, 2012, 04:42:05 PM »

You are probably driving it too hard!

Just kidding.

JC
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JC
Invermere, BC
1977 MC5C, 6V92/HT740
wg4t50
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« Reply #2 on: December 01, 2012, 07:44:06 PM »

Blower seals would be a good start to snoop out.
I would replace blower if that is the problem, with a turbo model, better seals I am told.
Dave
« Last Edit: December 01, 2012, 07:58:07 PM by wg4t50 » Logged

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luvrbus
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« Reply #3 on: December 02, 2012, 04:46:28 AM »

I think it is called 8v92 fever lol most of the time bad blower seals smoke at all speeds,give us the number off the blower and someone can tell the percentage of air it produces 

I have some 8v92 blowers they work but are about a 1/4 inch longer if you need one

good luck
« Last Edit: December 02, 2012, 04:56:47 AM by luvrbus » Logged

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bevans6
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« Reply #4 on: December 02, 2012, 05:01:01 AM »

FWIW my old engine did exactly that, smoked blue bad at the first startup run in the morning, then was fairly clean all day.  It was, after I took it apart and looked, totally and completely dusted due to a bad air cleaner.  It ran great too, just used a gallon of oil every 500 miles.  Hope this is NOT the reason yours is smoking...

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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white-eagle
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« Reply #5 on: December 02, 2012, 07:46:35 AM »

FWIW my old engine did exactly that, smoked blue bad at the first startup run in the morning, then was fairly clean all day.  It was, after I took it apart and looked, totally and completely dusted due to a bad air cleaner.  It ran great too, just used a gallon of oil every 500 miles.  Hope this is NOT the reason yours is smoking...

Brian
Bad, or old and dirty.  I just put a new Wix air cleaner on ($120!!!) and would hate the think that puppy could cause an issue.  It was running fine on the old 6  year old one, just thought i'd change it out with the other filters this year.
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Tom
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Rick 74 MC-8
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« Reply #6 on: December 02, 2012, 08:06:46 AM »

Rick

 I'm watching this very close. I too have blue smoke issue.  Seems to to be more pronounced after a long run at highway speed then pulling from a stop light.


         Rick 74 MC-8 8v71 na 740
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bevans6
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« Reply #7 on: December 02, 2012, 09:59:33 AM »

My problem was the stock old oil-bath air cleaners had no oil in them for around 40K miles.  The grit inside the air-box was impressive to say the least.  Pull an air box cover and look inside, see what you see.  Mine had caked on grit and grunge filling the grooves inside the air box cover.  It was like someone had poured a cup of fine sand inside the engine.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
RickB
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81 MCI 9 smooth side 8V71 Allison 754




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« Reply #8 on: December 02, 2012, 03:16:20 PM »

Brian that has been a sneaking suspicion for me for awhile, with the difficulty of getting a good seal between the top of the air cleaner housing and the inlet on the chassis I've wondered more than once whether a poor seal would allow dust into the motor. I guess I always figured that any air coming through the inlet would have to go through the filter one way or another.

There is some truth in my desire for an 8v92 repower but we are not using the bus enough to pay that kind of money to get it done. There's a chance that the young artist that I'm producing may have to do some extensive touring this next year and there's a pretty good chance that my partners would be willing to spring for an engine change.

I'm gonna scope the blower and I'll be looking for evidence of oil leakage through the seals. I'll update as soon as I get a chance to do that.

Gosh the bus ran absolutely flawlessly as I drove my friend Bryan White to a gig in the Wisconsin Dells. I was careful to do this as a "favor" with no pay as I'm not interested in the whole commercial license / tax issues again.

Hoping I'm not following your footsteps Brian

Rick
« Last Edit: December 02, 2012, 03:51:13 PM by RickB » Logged

I will drive my Detroit hard... I will drive my Detroit hard.
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