Tons of blow by on my 6.2l diesel!!

[J-ROD Diesel]

Well iv about given up. I have a 1987 m1008 CUCV with the 6.2l detroit diesel in it. The problem is it blows allot of smoke (blow by) out of the oil filler tube. when i say it puffs it out i dont mean just a little here and there i mean you can see it running with the hood closed! The funny thing is it only does it at idle but as soon as you give it hardly any throttle it clears up immediatly? The engine was rebuilt about 9,000 miles ago and havent pulled anything real hard scince the rebuild. It has a banks turbo as well. I dont think its a cracked head as I have had them in the past and shows no signs of it. I have also run a block tester kit on it and came up clean with no exhaust in the radiator. what do you guys think?? a cracked ring maybe?? any help is apriciated!!

 

[towcat]

blow-by is not measured at idle. it is measure just off idle to 900rpm. kinda hard to determine on a GM since we're not blessed with OEM tachs on this generation trucks. there's not enough mileage on the rebuild for you to condemn so soon. hang in there. the GM section is not as quiet as it appears. there's actually much in common with the detroit 6.2/6.5 and the IH 6.9/7.3.
research your questions and post when you can't find the answers in the archives.
welcome!

 

[J-ROD Diesel]

Thank you towcat! I have looked into almost every possible resource I have and have come up with nothing! I also own a 7.3l idi with 300,000+ miles on it with no smoke at all? I just figured I'd check here before I had to start tearin it down to see what's wrong with it.

 

[Black dawg]

The filler cap isnt supposed to be vented, is it?

 

[J-ROD Diesel]

Im not really sure to be honest. I just know it coming out of it like steam out a train whistle!

 

[towcat]

there is a vent on the earlier filler cap. it is for air intake.
later trucks have the CDR draw off the filler tube so the cap is a bad idea.
how is the condition of the CDR?

 

[J-ROD Diesel]

It is working perfectly just like it should. I replaced the system and there are no leaks in the lines.

 

[towcat]

It is working perfectly just like it should. I replaced the system and there are no leaks in the lines.

then the only other thing to do is load the dogshit out of the truck and go find a steep hill and work the motor hard. you need to seat your rings.

 

[J-ROD Diesel]

I kinda figured theyd be seated as good as they are going to get by now?

 

[towcat]

I kinda figured theyd be seated as good as they are going to get by now?

have you been nice or have you been working the motor hard?

anytime I do a ring/bearing/reseal it gets worked the moment the install in done and checked out.

 

[J-ROD Diesel]

Well I do live in the mountains and have pulled probably no more than 10,000lbs up some steep grades but didnt just floor it! The funny thing is it hasent started doing it except in the last couple hundred miles of the 9,000 scince the rebuild. thats the only reason I dont think its a ring not being seated and more like a faulty ring?

 

[towcat]

Well I do live in the mountains and have pulled probably no more than 10,000lbs up some steep grades but didnt just floor it! The funny thing is it hasent started doing it except in the last couple hundred miles of the 9,000 scince the rebuild. thats the only reason I dont think its a ring not being seated and more like a faulty ring?

if you have a bad ring you would have smooth idle issues. does it shake at idle?

 

[J-ROD Diesel]

No. Infact if it didnt smoke you wouldnt know anything was wrong with it!

 

[towcat]

No. Infact if it didnt smoke you wouldnt know anything was wrong with it!

quit being such a worrywart and run it!

 

[J-ROD Diesel]

haha! Im just scared if i run it and something is wrong with it I may just be doing more damage!