What Is Blowby? What Is Too Much Blowby? 

I’m currently in diesel technology school as we speak this channel help me with everything I’m a fan till day I die lol you really don’t understand how much this has help me

Good morning Josh! Came back to this video as we have a truck in the shop that had combustion gasses in the cooling system and it received a long block (PACCAR MX-13). The truck now has blow by both out of the oil fill tube and the crankcase tube. For transparency the technician that did the install was inexperienced and did not replace the oil cooler or flush the oil module (Claims there was no metal) and they used about a half a can of ether over the course of an afternoon as they could not get the truck to start initially (Bad High Pressure Pumps). CCV filter has been replaced. He was told to drop the pan and inspect the liners from the underside. He found a small vertical mark on cylinder 2 and orders from above were to replace the liner and rings on said cylinder. He stated to me he couldn’t really feel it with his fingernail. I don’t believe it will solve the issue. After his repairs I’m looking to come up with a strategy to isolate the source of the blow by. This is what I have come up with: Bring truck up to operating temperature. Verify blow by. Disconnect air compressor inlet and outlet to isolate air compressor. Run unit and revaluate. Pull rocker shafts off to ensure closed valves. Remove turbo feed and drain tubes from block. Pressurize turbo inlet to check turbo and intake valve seal integrity. Revaluate unit. With the rocker shafts out pull all 6 injectors and perform a cylinder leak down test on each cylinder. Wanted to see if you have any input? I can email you a video of the blow by and the mark the technician had found. It was his first major engine job and I’m preparing to take over his work.

This is my first time viewing your videos and I have to say I am now a fan! Great info! I used to work on Caterpillar truck engines in late 90's early 2000's and have seen this myself. I remember getting some with a scored cylinder pack that would puff fumes out of the blowby tube every time that cylinder fired. I miss working on these engines since I have been out of the game for almost 12 years but I am slowly working back into it looking to re-start my career in diesel repair.

This was very helpful. Thanks, i was trying to gauge how bad my 04 5.9 was.

Remind me of a truck at work, had blowby as bad as the RV and burned 8 gallons of oil a day. They used it that way for about 10 months

Your videos have been very helpful I just wish I had seen them sooner. There is a lot of things some shops can't check but they won't tell you or they don't know how. They were also enlightened. At my expense.

A turbo may cause crankcase pressure but by definition is not blow by. Blow by is literally gases blown by the rings in a cylinder.

I have also heard that if you removed the oil fill cap - and feel strong puffs of air coming out of the oil fill hone (with engine running) - that often means the rings are bad.

I know nothing about engines but removed my oil filler cap on my diesel and it was puffing air out like a steam train. No smoke or colour, just air and oil.

Thought I'd mention that different engine manufactures run this test differently, i.e. idle no load to high idle no load. Just so the viewer knows but depending on engine manufacture you can have other causes of high blowby. Such as a bad air-compressor. A leaking intake manifold/valve cover gasket bad oil seperator. It's getting to the point now a days that the rule of thumb is getting thrown out the window. Love your videos keep them coming. :)

Just because something makes sound through a mic crackly doesn't mean that sound is called static. Static noise is only caused by stray electricity or bad tuning or signal.

I guess this one qualifies as a destruction of the week at the end lol.

I used Xado Atomex totalflush and after oil change, Rislone Compression repair when my car got excessive blowby and oilburn. It actually worked.

Thanks for this

Removing "broken" exhaust manifold studs would be a GREAT video !!! Just saying

So accurate. I always said when a Cat engine idles and it has that sweet oil smell it's going to blow up real soon. Also I don't know why some Cat liners have a real noticable taper after many hours verses a Cummins..Maybe because Cat depends on Two compression rings as other manufacturers use more rings for this purpose.

Thanks for the good info mine dont look bad after that lass one in the vid!

I’m interested in that tool to measure flow out the blow by tube. I currently use a manometer and that is a lot less hassle.

Thanks great info, I work on much larger engines (c175) and trucks 793f/d) but still very informative.

I have a 3406e.. Blow by is not excessive. Yet it will blow off the oil fill cap fill cap or the dipstick if it is not tied down under load.. blow by tube is not clogged or restricted

My c15 acert had tons of blow by when hot. After replacing my high pressure turbo it all cleared up.

Hi u simplify technicien information and put it in excellent order , this simplify things

Great videos. I deal with CAT engines all day in the military so it was pretty awesome stumbling across your channel.

Great information I have a question about blow-by. What if you have blow-by at idle and it goes away when you Rev up your engine. What could be the cause? Thanks

Great video Josh greetings FROM THE UNITED STATES VIRGIN ISLANDS IN THE CARRIBBEAN US TERRITORY ST.THOMAS I AM A NEW SUBSCRIBER TO YOUR CHANNEL YOUR VIDEOS ARE SPOT ON I AM A JOURNEYMAN HEAVY EQUIPMENT MECHANIC MY DAD TAUGHT ME ABOUT HEAVY DUTY TRUCKS AND EARTHMOVING EQUIPMENT REPAIR HE PASSED AWAY LAST YEAR 2019 SO I AM GOING TO PERSUE THIS TRADE FULL TIME SO I AM WATCHING YOUR VIDEOS ON YOU TUBE AND READING SERVICE MANUALS AND I AM GOING TO GET MY CDL SOON THANKS FOR THE GREAT CONTENT GOD BLESS YOU AND YOUR FAMILY KEEP THE VIDEOS COMING

Nice explanations,thanks; And if the crankcase is pressurized,the oil cannot drain down from the turbo? and ends up in the intake pipes,and then,you have a lot of blue smoke from the exhaust? And,that can lead to engine RUNAWAY???!!

Just did an overhaul on my c15 accert at the rush in pharr tx. Well right of the bat I have blow by . Engine blows smoke like a high mileage Detroit diesel. Took it back and they said it run it for a few months before making a insurance claim. I told them if it could be turbos or air compressor. Well they said it could but they don't know how to physically check if they're bad or where the blowby is coming from. Well I ran it 26000 miles and I'm tired of seeing that smoke. Tomorrow I'm taking to cat and have them figure it out I hope it's not a bad installation.

Can you provide the part number for the meter device shown in the video?

Hi Josh :) Again a lot of useful informations ! My 3208 has a little of blowby from the crankcase breather. Not so much, but there is. I have the valve lash to do (quite 3000 hours on the engine clock) and I guess it was never rebuilt. I just ordered an oil sample analysis to see what's going on.

Curious... '03 Cummins ISL (8.3), at start up should I have a pulse/pressure coming out of the oil fill? ZERO smoke, just pulsing air. Is that normal or a sign of something? Thanks so much for all your videos!

I have a Mitsubishi Fuso FE160 2012 they say excessive oil in the turbo hi crank case pressure truck runs fine doesn't use any oil but they are saying to replace the engine

I've had 2 trucks....2ws and 6nz... both had high blow by... both ended up being bad air compressors pushing air into the crank case. Both diagnosed by problems building air and excessive oil in air tanks.

Very informative. Thanks for posting! 🙌

Hello , I was looking for a video where you talk about a truck with a new rebuild had a blow by for idle too much

very good information, keep em coming

I got mbe4000 pre emissions This happens only on cold star 80 to 90 degrees in the am Engine star shaking hard to crank up Engine light comes on..but it goes away 3 to 5 minutes later.and truck like a champ..I seen a decline on oil pressure too

Got a Cummins N14 with excess blow by still after the rebuild. Replaced air compressor, had the heads checked up again, replaced piston rings again, and still showing excess blow by. Any suggestions?

Hi,i love your videos they are educational.Iam from Australia. I have 2014 kia sorento diesel2.2 oil coming from turbo it has only 29000 miles on it.put new turbo still have the same problem ,any suggestion please I need your help,thanx so much to you and every one watching the channel

I have a lot of blowby after chilli.......but seriously great vid your a good teacher.

I can’t stop smoking crack

It's official an in frame and turbos. I'm like Johnny Cash I got it one piece at a time but it cost me every dime. I think these shops know exactly how much money I have.

I have a 6.7 Cummins deleted, I take the oil cap off after it is at operating temperature and there is a steady vapor trail, I put the cap on upside down but the cap will not move at all so this is a good thing but is the vapors normal? Sorry about the dumb question.

Can a bad air compressor cause a ton of blow by and low oil pressure? Great videos!

Apeman, wouldn't you say that twin turbo Acerts, by their very nature, produce more blowby then their predecessors? Thanks for all the great vids!

my cat 3116 have blow by after the engine warms up ? Could it be the engine or the valve seals ? I had a overhaul engine rebuild about 60 000 miles ago and unless something was done wrong I don’t think it’s the block

Good informative vid, I have a 16 6.7 f350 with a ccv delete, I do get a slight haze at idle but nothing crazy (265K kms) Could I take my pickup to a CAT garage and have them perform this test?

I'm probably thinking of it more in a petrol engine sense, with a petrol engine you just get smoke, with a diesel the seals go, and you get a runaway ;)

Good vid.

My 2006 isx Cummins was rebuilt 2yrs ago and it has blow by coming out the dip stick and oil cap. I replaced my turbo,crankshaft adapter, crankshaft speed ring, and Cummins dail pin. Im sure what else to do, it burns diesel I feel to much.. Can somebody respond to this please…

Awsome video!! We want MORE cat C15 specific videos...the videos would help save some money if I can do my own labor

Thanks for your informative video.

I have blowby on my 05 C7 but the engine runs good. If my engine stating to wear out is there a lubricant I can add to the engine oil besides Lucas ?

He sounds like he’s hiding a heavy southern drawl to me...

I feel the pain 30K

I need that blow by measuring tool

Adept ape where can i buy that caterpillar blow by tool in the video I'd like 1 to test my cummins

Have a 04 peterbilt 379 with a cat c15 mbn, it stars dripping oil through the blow by tube, when i drive it for an hour or two, what can caused this?

I got a 2006 isuzu fvr with isuzu motor 280k miles on it...I have blow by but the truck seem to rum good..I do have a check engine thT won't clear but no code...have you ever seen that...

Have a new brand perkins 1104a 44t engine and I'm getting oil coming out the dipstik and slight smoke

Very informative. Keep em coming.

Thanks for the tips! How long did the owner/driver run the RV like this? What % of power do you believe was lost? Fuel mileage percentage?

Good piece of troubleshooting technq

This problem started after I got a cat reman Ecm I was told to get new injectors I did. Then I was told to have the new injectors pressure tested. I did there were two hanging up I was told. Several dyno pulls later still no change. Oh and a bar and plate air to air. Just now tried a new ecm. No change. I've got to figure this out before I'm broke. Oh but wait now they want me to buy two new turbos. This has to be it.

What about measuring blowby coming off a bowl? 💨

4.5L turbo intercooler diesel Runs perfect, idling perfect but burns oil (blue smoke, smells burnt oil) when accellerated or put under load. Smoke comes immediate at metioned, smoke stops immediate after load release. Whats your educated guess ?

How could poor pump timing affect blow by?

What of engine breather is bringing out oil

Whats the part number for that blow by tool?

I have a 2007 kw with cat c15 twin turbo with 770000 miles and it has smoke and oil coming out of breather tube not as much smoke as that rv in video but enough to see it when idle and oil in a 2500 miles per week im putting maybe 2 to 2.5 gallons of oil can any one give me an idea of what the problem could be??

What happens on a diesel if you eliminate the valve seals turbo and air compressor pull apart the engine and the liners and pistons have not al wear. What could be causing the blow by

Great videos sir. Thanks for all the masterful knowledge. I have an '07 W900 with a C-15. Last week it blew the oil fill cap off & pushed out 4 gallons of oil while pulling a load. I replaced the cap & oil and within 10 miles it did it again. We put a pressure gauge on the filler neck & without a load were only able to generate 1-2lbs pressure. A compression test indicated all cylinders are sealing within spec - they should be as this engine has 17,000 miles on it since a complete in-frame. The thought is that the high-pressure turbo has lost its oil seal & is pressuring the crank case. Before the expense of replacement is there anything you would suggest we look for? Thanks again, my son & I really appreciate your vid's.

can a loose injector compression is leaking past be a root of blowby.

Thanks man for valuable info.

I had a customer with a Acert c7, and it was almost like this at 8:26, and turned out to be a cracked injector.

Can you do another blow by video

So it means a new engine or rebuild ? And how much approximated price for cat 3126 rebuild ?

Where can I purchase one of those blowby meters ?

thank you man

I have an engine (C15 acert) and it has oil leaking at the top of the air compressor. Is this due to blow by or just something that's common with the air compressors?

Great Video I Really Enjoy It

I'm seeing oil leaking from the intake hose seals next to the turbo and also from the oil cap. Compression test was done on this engine a few years ago and it was perfect, also I don't see any smoke from the exhaust or loss of power. Is it likely that turbo seals are the problem ? I looked at PCV valve too and at least some air is escaping from it when idling, so it's not fully clogged or something.

My 1998 3126 7.2 starts only with startin fluid in the mornings. What can be ???

Great video, can’t seem to find a blow by gauge for sale lol, I see stuff by jtc but no way to buy one lol

It could also be Oil Seperator!!

What about if i have oil coming out of my C-15 blowby tube? Not a lot of oil but when I park for 10 minutes there will be a couple drops on the ground, I hardly have any blowby tho

Very helpful

Your videos are all very helpful. I have a Peterbilt with C13 DPF filter and I want to swap it with a C15 with no DPF filter. Is that legal? I don't run Cali, only stay in the north east.

Good info

Great video man! good to know info

Did a rebuild on my c15 accert 2007 and it has blowby it was measured at 500 but I have doubts. The turbos where inspected and the didn't need to be replaced but im not sur how to pin point this problem or if they just used some of the same parts. It is still under warranty but do not know how to ask for in the holt cat dealer.

Where is the primary and secondary speed sensor location on a 2001 c15 6nz?

I used blow by to help me diag a failing turbo on my 03 Cummins. Got the truck @ 207K no blow by issues noted at the time. 217K later I start noticing oil seapage out the CCV seal and oil cap as well as the turbo drain tube hose. I'm also running richer than normal with alot of soot under the bed (4ft of my exhaust broke off so it dumps under the front of the bed). You can smell it. I get it up to operating temp one day its around 60* ambient outside so I lean on it to get it to 190*, pull over pop the hood check my CCV while flicking my throttle lever. I notice a high pitch sound as the turbo is spooling down from me reving the engine. I put one hand on the compressor housing and flick the throttle lever again, the comp wheel is vibrating back and forth as it slows down from high rpms. A few obscene words later and a 15min drive back home I pull of the intake and wiggle the wheel not only to find it having excessive axial play but an oil seal has broken internally. So I put everything back together and get to thinking. I have a known compressor side leak, If at load or highway speed; that wheel is building enough pressure to push back against that blown seal to send pressure down the oil return to the crank case, It could be causing the increase in crank case pressure that im seeing. I'm now awaiting a used HE341W from Indiana to rebuild and drop in to test my hypothesis.

Hey my friend you did mention that bad air compressor can cause blow by.does that mean if you fix the air compressor you won't get no more blowby?

i have hino e13c engine,.too much smoke coming out from the breater..what is the cause..the smoke is the if you are smoking.

H Josh i have question i got c 15 bxs recently rebuilt is runing like 600 hundred miles and is have it oil by the crank case breather when stop i see it

Great and very helpful.. I was wondering if you could help me with my 06 accert just had platinum done on it about 15000 miles on it.. we changed all the fuel lines both fuel filters based and fuel transfer pump.. it’s getting lots of blow by and running like crazy ruff on idle.. I don’t know what else I can change on it? I would really appreciate your help on this please thanks

Great video! Thx.

Thank you sir

I have a 94 Ford ranger 3.0 v6 I have low compression in Cylinders 3 & 5,- 60 lbs & 95 lbs the motor has no power and a bad Misfire, And I have air blowing out my dipstick bigtime So Im assuming that its my lower engine ,I don't know if its worth tearing down the motor to see what's going on This motor has only 56k original miles on it... Please help What should be my next step ,After the compression test the motor will not start and the spark plugs & Cylinders are pooling with gas ,I have spark gas air and timing is correct ,What should I do now ?The motor did run until we did the compression test now it smells like gas and it will not start ,I pulled all the spark plugs let it air out for three days put New plugs in it It has New fuel pump & filter coil complete tuneup ,When I bought the truck I had it checked out by a auto shop they told me the motor was good I put $1500 into it Now this !! I don't know what to do

I have oil in my cooling. It a little. I installed air compressor last year. No water in the oil. I'm thinking oil coller.