It says to pop off the oil fill cap to check for blowby...

Mine has a very light haze, is this blowby?

I also have a light haze from the breather tube and the dipstick tube (when its pulled)

No smoke, but a light haze...

I've never seen "smoke" coming from either location on any truck...

Whats it look like?

Actual white thick smoke?

Or haze?

 

I dont really know, But whenever I pull mine off, I get a very small haze.
Kinda like in the winter when you see your breath, But only half of that.
Is mine normal, I think so because it dont use any oil of any sort, I definately got power. And I aint burnin oil, only leaking it in some areas
Wheelo

 

Yeah, that's normal. All of mine have done it to one degree or another. Still nowhere near what my 6.9/7.3 IDI Ford did, though. One of them got the filter changed every 5Kmi; the oil got burned twice that fast. If your engine has a slight haze at idle (blowby, not exhaust), it's fine.

Daniel

 

Most of the time when a company buys a used Class 8 or 7 truck , they have the truck dynoed to check for Horsepower and blow-by , that give them a indication of what the engine health is. even for your ISB or 5.9 B , you can have it dynoed check . they will use a orifice on the blow by draft tube to check for blow by with a manometer while the engine is loaded down.

 

Make your own blowby tool.
The Cummins blowby orifice tool is simply a tee with one .221" (15/64-in) outlet. 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. They sell them at the Cummins, but I have made my own plenty of times, less than $10. A simple manometer can be made by looping into a 'U' 6 feet 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

The reason for multiplying by 2 is that inches of water equals the water rise in the open end of the tube plus the inches the water is pushed down on the engine side of the water tube. For simplicity my numbers below are the measurement of rise only.


Cummins new 5.9 engine numbers are:
63 liters per minute(2.5" water rise) @ 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

Beside indicating a compression problem the valves could also be out of adjustment.

Another way (mine), 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. Other tubing end remains open. Use a sharp tipped felt marker to mark the water level with the engine off, have a helper 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 the distance from engine off mark then multiply each by 2.

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

 

Bill, Those figs can be thrown off too if your vacuum pump is discharging a bunch of air into the crankcase from a big vacuum leak on the inlet.
I noticed a lot less blowby after I discovered and fixed a huge hole in the rubber elbow fitting going into the vac pump nipple.

K.

 

Cummins has changed the orifice size to a .302 , the smaller orifice is no longer used.

 

hi

while looking for a oil leak under truck with engine running i am getting a light haze comming from the breather tube .

seams to be a fair amount of air going through this tube , is this normal ?

just for fun i put my finger over hole for a few seconds and released it .

did not take very long for engine to build up a fair volume of psi that came rushing out , is this normal ???

engine does not seem to smoke out the exhaust any .and runs smooth .

i may need a valve adj , as they sound loud to me but it is my first cummins ?
could anything other than blowby cause this ?

if i put a vacuum gage on the vac pump what should the reading be ?

does not seem to use much oil even with the leaks i am working on , but i have not been pulling / hulling anything yet .