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Cummins NTC 350 Help

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BrianS11388

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Jan 9, 2020
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Albany Oregon
Hello everyone, I've got a cummins NTC 350 with a CPL of 021 In a peterbilt 359. Lately it's been pouring out blue smoke at startup, idle, and at normal operating temp. I replaced the injectors and it still smokes know matter the temp or the amount of load on the motor. I recently ran the overhead on it using the inner base circle method within change in amount of smoke it pours out. This cummins has over 800k miles and I've never opened it up to check rings or anything like that. We bought it for a farm truck and it hasnt always smoked this way. Any information would be greatly appreciated. Thank you.
 
Truck Shop

Truck Shop

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My first Question is when did it start pouring smoke? Second remove the exhaust head pipe and look inside turbo to see if exhaust compressor wheel is wet with oil.
 
Truck Shop

Truck Shop

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Well you are dealing with a fixed injector timed engine with that 855 Cummins and those were the same
right up to early Big Cam IV engines after that Cummins went a STC injection timed engine to cut back
the smoke on start up. All the small cams and early big cams were smokers. With that said check around
the exhaust manifold area were it bolts to heads, sometimes they can run wet running out between the
gasket, that will tell you if you have a wet cylinder. the other is use a infrared temp gun and check the
manifold for balanced temp at the ports where it meats the heads. Should run 275* after a few minuets.
But Remove the head pipe at turbo and check that.
 
Truck Shop

Truck Shop

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Well either it has broke some rings on #1 cylinder, or you have some liner O-rings leaking coolant that scuffed the piston and bore, or an injector is puddling fuel at a great amount.
Next thing I would do is drain the oil and drop the pan, roll the engine over so you can look up and check the piston and liner for scuffing and coolant droplets collecting on the bottom of
the liner. While you there you can have someone bar the engine over and check the cam lobes for wear. If you don't have a way to pressurize the radiator to make the liner o-rings leak,
just let it set awhile like a few days and check now and then for coolant on bottom of liner or on the steer axle and floor. When those o-rings go bad it won't stop leaking. When you pull
the oil drain plug just let a little out first to see if there is coolant in bottom of oil pan. By pulling the pan first you can check several things at once for only the cost of gasket and oil. The fuel that's leaking down the side
of the heads is probably the o-rings under the fuel crossovers leaking. Or it,s a mixture of oil also leaking
from the rocker box seals on the end of the rocker shafts.
 
B

BrianS11388

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Messages
45
Location
Albany Oregon
Last week I changed the oil, it was over the full mark and there was fuel in the oil. But I do plan on dropping the pan. Thanks again for your help. I'll keep you posted.
 
Truck Shop

Truck Shop

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When you set the overheads/adjusted the valves did you set the injectors and valves at the same time on each cylinder? And how many inch lbs on the injector preload adjustment?
 
B

BrianS11388

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Location
Albany Oregon
No sir. I soun the motor around to Mark A on the accessory drive pulley. Found which cylinder had the valve train that was loose which happened to be valves on #5. Checked them and adjusted injector on cylinder #3 to 6 inch pounds. And followed procedure from B to C and back around to A etc.
 
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Truck Shop

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Do me a favor and take photo of the cam followers on the left side of the block just below the injection pump, please. Just to make sure we are on the same page.
 
Truck Shop

Truck Shop

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By that It should be a small cam, but get the photos so we know what we have. That has a date of 10 of 72, by what I can see in that photo. And there were no Big Cams in 72.
 
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