Can anyone tell me what blow by is?

[MCervinka]

Can anyone tell me what blow by is?



Is this bad on a remanufactured engine?



Can anyone tell me what would cause blue smoke at startup only when cold?

 

[TimG]

Blow by is the compression in the cylinder that is force by the end gap of the piston rings. All engines have a certain amount of blow by. The blue smoke at start up is oil that has leaked into the cylinder thru the valve seals while the engine was not running.

 

[jelag]

Let me add to the post that Tim posted, with respect sir... .



As the engine wears (rings) more and more of the gasses at the time of the explosion will go past the rings... this washes down the cylinders with some high pressure gases and will force these gasses with some oil out the breather system... . the more wear on the engine the worse it gets... .



He's right on the money with a puff of smoke when the engine starts... as the engine cools... the heated oil will drift past the valve guide oil seals down the guide and can puddle on the back of the valve... as the engine starts it takes in this oil and burns it... once the engine heats up the seals do a better job sealing..... and what does go by is in smaller quantities... ... in most cases, you can put the piston to TDC (top dead center) pop off the keeper and spring and replace the old and hardened valve guide oil seals... they get hard and brittle with age... . however modern engines usually have valve guide oil seals that go the life of the engine.....



Hope this adds a little... .

 

[Vaughn MacKenzie]

Blue smoke on a Cummins in the morning though is more likely fuel not burning completely due to cool cylinder temps. It could be a bit of oil but most likely fuel. Sniff the exhaust. . . if it's strong stinky diesel odor. . . it's fuel.



Vaughn

 

[Snoxracer]

Blow by is what happens when a Powerjoke or a Undurablemax trys to keep up with a Cummins! You Blow By them!!! :-laf



Snoxracer

 

[MRosinski]

Blow by is what happens when a Powerjoke or a Undurablemax trys to keep up with a Cummins! You Blow By them!!! :-laf



Snoxracer

Now thats funny, I don't care who you are.

 

[RTillery]

Blow-by is the present tense version of the old Roy Orbison classic: Blew-by-You!!!, a famous song about old farts in diesel pic-ups smoking smart-alec kids in ricers with whale tail spoilers and coffee can tail pipes.

 

[bzingre]

Blow-by vs. Carryover

A lot of time we mistake oil carryover for blow-by. Blow-by is the actual combustion gas that has passes the rings and has to have somewhere to go. That pressurized gas leaves the engine from the fumes disposal group i. e. blow-by tube. In 2007 this will be eliminated on all engines because the air coming from the blow-by will then be considered (by EPA) as part of total emissions of the engine. I most cases, that gas will be recirculated back through the intake of the engine.



Now for carryover. Sometimes, if the blow-by is high enough, or when the engine is extremely overfull of oil, some oil comes out of the blow-by tube. This is oil carryover, and is not normal. One drip every now and then is OK, but excessive oil from the fumes tube should be examined. That "smoke" you see is mostly hot combustion gas condensing against the cold outside air.

 

[Scrappy]

A reman engine will also have more blow by than a broke in engine, the rings in the reman are not seated yet and it bypasses more air

 

[gtobey]

Let me add to the post that Tim posted, with respect sir... .



As the engine wears (rings) more and more of the gasses at the time of the explosion will go past the rings... this washes down the cylinders with some high pressure gases and will force these gasses with some oil out the breather system... . the more wear on the engine the worse it gets... .



He's right on the money with a puff of smoke when the engine starts... as the engine cools... the heated oil will drift past the valve guide oil seals down the guide and can puddle on the back of the valve... as the engine starts it takes in this oil and burns it... once the engine heats up the seals do a better job sealing..... and what does go by is in smaller quantities... ... in most cases, you can put the piston to TDC (top dead center) pop off the keeper and spring and replace the old and hardened valve guide oil seals... they get hard and brittle with age... . however modern engines usually have valve guide oil seals that go the life of the engine.....



Hope this adds a little... .

Here's a link that will allow you to see what goes in inside the engine. When you view the piston going up and down, just imagine that the rings(in the grooves of the piston) are not sealing against the cylinder walls, and the compressed air in the cylinder escapes past the rings down into the crankcase, and out the tube on the front of our Dodges into that little condensation bottle. How a diesel engine works!

 

[jwilliams3]

Blowby is what happens to person that eats too much protein in one day.

Or at least it happens to me!

 

[JasonCzerak]

Let me add to the post that Tim posted, with respect sir... .



As the engine wears (rings) more and more of the gasses at the time of the explosion will go past the rings... this washes down the cylinders with some high pressure gases and will force these gasses with some oil out the breather system... . the more wear on the engine the worse it gets... .



He's right on the money with a puff of smoke when the engine starts... as the engine cools... the heated oil will drift past the valve guide oil seals down the guide and can puddle on the back of the valve... as the engine starts it takes in this oil and burns it... once the engine heats up the seals do a better job sealing..... and what does go by is in smaller quantities... ... in most cases, you can put the piston to TDC (top dead center) pop off the keeper and spring and replace the old and hardened valve guide oil seals... they get hard and brittle with age... . however modern engines usually have valve guide oil seals that go the life of the engine.....



Hope this adds a little... .

After 8 to 10 hours of sitting in 70+ degree weather, my 43,000 mile old truck will start up blue smoke for 10 to 15 seconds. it smells like diesel, but's it's warm out. it's not like it's 32 and i'm using hte glow plugs to start. This still fluel getting past the injectors once shutdown.



And I let the truck idle down to about 290 degree EGT always. sometimes more if I got things to take out of hte truck that take a while.

 

[gtobey]

Jason, even though it is warm outside, the block temperature and combustion chamber are cool compared to their normal operating temperature. If your compression is near the minimum limits, then the unburned fuel will appear as a blueish smoke and smell raw and sometimes burn your eyes and nose. Oil that is sucked into the combustion chamber from the valves upon startup provides an additional "puff" of smoke upon startup but subsides quickly. The unburned "raw" fuel gradually decreases until cylinder temperature helps overcome it. Your turbo is not leaking oil into the intake is it? That is a source of oil to cause the blue smoke upon startup. I would hope that your rings and valve guides are not worn in only 40,000 miles.

 

[JasonCzerak]

Jason, even though it is warm outside, the block temperature and combustion chamber are cool compared to their normal operating temperature. If your compression is near the minimum limits, then the unburned fuel will appear as a blueish smoke and smell raw and sometimes burn your eyes and nose. Oil that is sucked into the combustion chamber from the valves upon startup provides an additional "puff" of smoke upon startup but subsides quickly. The unburned "raw" fuel gradually decreases until cylinder temperature helps overcome it. Your turbo is not leaking oil into the intake is it? That is a source of oil to cause the blue smoke upon startup. I would hope that your rings and valve guides are not worn in only 40,000 miles.

Well, on a cold start there are a bunch of little extra noises that are going on. extra "ticking". I'm sure it's just things that are cold and are waiting for the oil get around effectlivly. Some times it sounds like it's comming from the injector pump. somet times from the valve cover.



I should put a muffler on this truck and listen and compare to my neighbor's new 05 for noise.



Anyone had any issues with the CP3 pump breaking yet on the 3rd gens? I

 

[gtobey]

Have you checked the codes in your computer to see if there is anything stored such as a sensor not being read properly? If you have no codes set, have you ever really loaded your engine during the break-in period? In other words, have you worked it hard, or just driven around empty for the 43,000 miles?



What kind of oil are you using?