The crankcase vent on a B( fuel pump side of the block) has a chunk of steel wool in it, cummins calls it the strainer. Make sure that it is still there. It's purpose is to stop the oil from blowing out the tube and allow the oil to drain back to the pan. If that is still there, check the blow by with a manometer and the cummins tool, can get the P/n for you tomorrow at work. I work on Cummins all day.

 

I use a hand pump vacuum pump with a gauge, the same type that can be used to bleed brakes. Just follow the lines from the engine pump out connecting into the lines and pumping them down, the gauge should hold when you stop pumping. Not hard at all to do since there are only three vacuum circuits in most trucks.

 

You can make your own blowby measurement tool for under $5. A blowby orifice tool is just a tee with one .221" (15/64-in) outlet (pipe plug with a hole drilled in it). Connect one end of the tee to the end of the blowby tube. Put a manometer on last tee outlet. That is your blowby tool. A simple manometer can be made by looping 6' of clear tubing with water in it half way. Measure how high the water level rises with a tape measure, multiply it by 2, convert it to LPMs

Rough conversion is:1"= 27 lpm, add 3 lpm for each one inch (1/2'' of rise in the tube) of water

New engines numbers are;
63 liters per minute(2.5" water rise = 5" of water) @ 2200rpm,
76 L/Min (3.5" rise) @ 2500rpm
85 L/Min (4.5" rise) @ 2800rpm.

Worn engine that needs rebuilding are roughly double i.e.
126 L/Min(10.5"rise) @ 2200rpm
152 L/Min(14.5"rise) @ 2500rpm
170 L/Min(17"rise) @ 2800 rpm

Valves out of adjustment or a head gasket blown will also cause high numbers.

The way I do it, same idea, is to block the blowby tube with a 1/2'' pipe nipple with a cap that has a 15/64 hole drilled in it. Use 3/8'' id looped clear tubing with water in it slipped over the oil dipstick tube. Use sharp tipped felt marker to mark the water level with the engine off, have someone start an already warmed up engine and run the rpms up to 2.2, 2.5 & 2.8k rpms. Mark each water level with the pen, measure then multiply each by 2.

This is all very simple to do, just hard to explain with words

 

That will tell you that you have a leak. I already know that. It cannot tell you where. Would help seperate the circuits though.

 

infedel is right, B and C series engines need different size orifices.

 

any solutions on this? i just got my truck and on the first road trip of only 250 miles i lost 2.5 GALLONS of oil. it seems to be comming out the breather tube. the truck runs great, in my opinion. no noticable smoke excpt on startup. At least i dont have to worry about the frame rusting.

 

Hey mo,
on this particular unit there was a cap where the cam nut is we replaced that with a breather cap that had a drain back in it so all of the oil that was getting blown out just drained back into the crankcase, also we were releasing excess crankcase pressure thru another outlet.. This was cheating I suppose, but it worked and the customer was very happy. Good luck

 

hey demsmiths,
by cam nut im guessing it is on the head? what kind of cap is it ? something you made or found/ordered? i cant just run out and look at the truck - it is parked 20 miles from home. thanks

see this post under 12v engines here

 

the front cover, drivers side, basically where the blow-by bottle rests. cant say that I have this on my truck. but on the commercial versions its there

 

Infidel, Haulin, and alot of others on this site never cease to amaze me with their knowledge!
My truck has 102k and for the last 30k or so has alot of blow by. I thought it was my vacuum pump but it seems it's coming out the blow by tube (mine doesn't have the bottle). I'm going to try Infidel's directions and hope for the best.

 

Do you want to sell that block off plate, or ship it to me to borrow (I'll pay shipping here and back plus some for rent).

Or do you have a part number for it ??


I'm really beginning to think my problem is in the vacuum pump, altho when I rebuilt it, I couldn't find anything wrong.

 

the nut is actually the pump nut, and the cap came from cummins. sorry so vague! the cap is on the front cover.

 

so I noticed that i have a replacement oil filler cap that is not vented. is it supposed to be? maybe adding a vented filler cap would help.any thoughts???

 

The valve cover is not vented. The vent is up front on the timing case cover. The oil fill cap is not vented at all.

 

thanks for the pic and info. My 4b is obviously different , but I dont recall seeing a vent on the front cover. I will se if I can figure something out .