Ford 7.3 Powerstroke How to REALLY Check for Blowby On A Diesel 

Blowby is not caused by the gap between the piston and cylinder wall. Over time the compression rings wear the cylinder wall. When new, the cylinder wall has a crosshatch honed into the cylinder wall. That crosshatch holds oil and seals the compression rings. When that crosshatch wears away it no longer holds any oil to help seal the compression rings. Therefore that lack of seal lets combustion gasses blow-by the compression rings. True blowby is checked with a percentage leak down tester, which uses a spark plug hole for pressurizing the cylinder at TDC for testing. But with a Diesel there’s no spark plugs so doing a technical % leak down test is difficult. Also as a side note that is why it’s so important to do regular oil changes at 5k or less on a diesel. Diesel is a low refined fuel product, so it produces a lot of soot (carbon). That blows by and gets in the oil. Carbon is abrasive. So the dirtier the oil gets the more wear occurs. Another excellent method to clean oil and prolong oil change intervals is to install an oil bypass filtration system which can filter down to a micron. Then Oil change intervals can typically be extended to 15k on a 7.3L. But oil testing should still be done at 5k intervals to establish a baseline for each engine.

Thank god, I’ve tried to sell my truck and the guy came by and said it had blow by because of the steam but it passed the ping pong ball test at 236000 miles

I've been around a lot of 7.3's. As far as I'm concerned, that is considered zero blowby are completely normal.

My 350 has exactly the same amount of blow-by vapor at full temperature. It had that at 167k when I bought it and it now has 220k and it's running perfectly fine.

I, just bought my first diesel E350 with a 7.3 power stroke with only 499,000 miles . It’s fully armored and looks cool 👍 that pin pon ball would land in Jupiter 😂😂😂

Cool trick! selling my 2002 7.3 f350 and a potential buyer asked about blo by so here I am! Mine has 330k miles and the ping pong ball did the same as yours.

Most diesels have pressure. Flipping cap upside down on a vibrating diesel engine. Blow by usually coats your hand in oil.

I hope your having a Very Merry Christmas with the new toys and a Happy New Year getting said toys on the truck :) A little Blow-by is normal because that's an 18 to 1 compression motor, seen way worse on old 400k motors and they run fine... But after a test drive pop that filler cap off and tell the Used Car Salesman "This truck needs a new motor" and watch him freak out :) They might knock off $10 Grand on the price :) God Bless and keep the videos coming!

That vapor steam or mist is blow-by, its the combustion gases coming back out the oil fill.

Thanks for your videos. They help a lot. I have a 2001 7.3 with 371,206 and it appears I really don’t have much more blow buy than what you showed on this video. Two months ago I removed the drivers side rocker cover and noticed some oil sitting in the head which I have come to learn that o probably Hve some injector o rings that new to be replaced so that will be my next project. Thanks again

Nice trick. I’m gonna check my truck. 7.3 02 f350 lariat crew cab. Think 175,000 on it I bought it new. Been cared for my daughter drives it now 🐎 tows her horses at times.

I have an 02 7.3 with 95k miles. Very similar blowby results as yours. Good video brother👍. Don't worry about the vapor usually 95 percent oil. Big industrial engines I work on have crankcase vent slingers that drops the oil out of the vapor and return it to the crankcase. Catch ya on the next vid

So i got my truck a few months ago. i drove it to Dallas from San Antonio already and to College Station then a Florida trip. So fun to drive. it's a 2003 F250 7.3. Merry Christmas!

I got a 99 7.3L with 163k miles and I get the same amount of white smoke coming out the tube but the cap doesn’t budge at all. It freaked me out when I saw the smoke but it seems like your trucks running fine and does it too so I’m less worried now

Even a brand new motor is going to have mist coming out. This is a perfect motor. I would have no concern

I’d be curious to see that same test on a brand new truck.

Very nice idea. Never thought about using a ping pong ball. My truck is down right now....have the injectors pulled out to replace the orings and I'm having Mississippi diesel products rebuild 2 that are sticking cold. When I get her back together I'm going to try this trick. I know I get some oil vapor when I pull the cap, Very similar to what you showed in the video. Maybe just a skosh more but not enough to move the cap. Curious to try the ping pong ball now

My 99 has 330k on it that about the same if not less blow by on her these engine are tough take care of em and they’ll last a very long time

Damn man nice video! I’m about to buy my first 96 7.3! Excited and this video definitely helped! Thanks man

the exhaust gas in blobby is co2, co, and steam - steam is a large part of the combustion gasses - that is why water drips out of your tailpipe

I've got a 99 f250 with the 7.3. Has 415k km so about 260k miles looks identical to what you have in the video with your truck, I was worried when I pulled the cap off and saw the vapor but once I flipped the cap back down I only saw movement from the engine vibration. Still had me questioning it though. Will have to try the ping-pong ball.

If you measured the diameter of the oil fill opening, and the weight of the ball, you could figure out how many psi pressure it has. Or you could add water to the pingpong ball with a syringe, till it just stopped fluttering then glue it shut, then it it ever makes it flutter in the future, you know that the crankcase pressure has increased.

Beautiful! Merry Christmas, Thanks for another Awesome video with great info!

my 99 7.3 has zero blowby at 230k miles. it was very well cared for and never moved more then its 12500 gvwr i will have to check with a ping pong ball but i dont even have a vapor coming out. however on a 2011 6.7 we have at the shop with 150k miles...it cant even keep the oil cap on in the least

You have to let it warm up first for the test. Go tow 10k up a hill then check

I just traded this Cummins with a lot of blow by for a duramax with no blow by may have put a couple hundred miles on it then today I checked it cuz I was bored and it was blowing the cap around. Blow by seems like something that should happened over time the truck has 179k on it and it was barely shooting up vapor when I first checked it just blows my mind

Wouldn't the turbo suck some of the pressure out? Not sure if this is a great way to check blowby on 7.3Ls

Good video, I have a 99.5 that has 66,670 miles on it. I am the original owner and only one who drives it ( f350 4×4 4r100) It had 0.2 of one mile when I took possession. I changed the factory filled oil @ 500 miles with motorcraft 15w40. Then @ 3000 I changed the oil again and switched to Red line 15w40 full synthetic. And have changed the oil every 1k to 3k miles to this day.... I use it to tow a lx985 skid steer locally so it's not my daily driver. My blow-by looks exactly like yours. I was thinking I may have switched to synthetic too soon (@3k) and the rings haven't had time to seat properly? But it's always had the same amount of blow-by ever since new.

Very interesting, and inspired me to do the same test on my '99 7.3 w/ 293K miles. Had the exact same motion on the ping-pong ball! Perplexing. I've only owned the truck for 6 years, though I have changed the oil every 5,000 miles AND change the HPOP reservoir oil, and run Archoil additive. Wondering what a new/rebuilt 7.3 and a worn, ragged-out 7.3 would show on this "test."

The ping pong ball can be bouncing from vibration. If its not throwing oil up our puffing like a loco roll on

For blow by you should be talking and demonstrating with a 6.4 Power Stroke that thing can blow the cap in the air from new😂😂😂. Well not quite how ever it is quite exsive. Mostly because of the regen or burning off the diesel particles trapped by the DPF filter the system dumps fuel into the back two cylinders to increase the exhaust temperature to from 900% to 1200% this incredible amount of temperature causes things to expand. A lot. So the rings are fitted loosely meaning the gap in the rings are much wider so that during this expansion the ring gap doesn't close up and cause damage. So now during normal temp the gap being mutch wider causes high blowby. I have heard that this causes so much fuel to get past the rings that at oil change time you can get an increase of 2 or more liters/ quarts that is a lot of diesel in the crankcase. This has been the #1 suspect of premature engine failure and that of other moving parts.

happy holidays man great video

I picked up a 7.3 van and was concerned because it has waaaaay more blowby than my truck. Turns out my truck is just a freak 7.3 with almost no blowby at 200k

Quick question what do you do for work? Because you know how to blow some coin on a 7.3 my friend. Last question? Why do you choose to upgrade an older truck when you can clearly purchase a newer one with less mods that produce better or the same outputs and gains? I have a 7.3 and I have my reasons why I dont want to by newer, what are yours?

manometer on the breather tube is the only way to actually check it against the spec from international, and when fully warm Also, blowby is from worn rings, not piston cylinder clearance..

Thanks for sharing. I guess I should test mine it has well over 200,000. Best Wishes & Blessings. Keith Noneya

6.7 powerstroke guys have more pressure then this. High compression engine for you.

Your oil cap never had a chance up there, it never could stay there without you saving it...At 150,000 miles it is just breaking in...Give it a chance, oh you sold it... I really enjoy your videos by the way, FYI.

Looking to buy a 2000 7.3 with ~65k miles (proven miles) and it has much more blow by but it does have 80%over injectors and a KC63mm but im not sure if its a bad sign or not considering the injectors.

Old video but I'm hoping you'll see this, so I have smoke coming from my dipstick, but I took the fill cap over the fill hole and it just kinda vibrates a little bit until it falls off. Is there any reason for that?

How many miles is on this truck during this video?

I am a really easy driver on my truck. But recently my dad purchased a new truck and me and him had a little race. When we were driving it slipped out of overdrive and hit at least 3k rpm for about 2 seconds. It scared the hell out of me. When i got home i was a little worried as I dont ever rev that high. So I checked all the fluids and I decided to check to see if i could feel blow by. I dont feel anything but its the first time ive ever seen vapor coming from my fill cap. It was a colder her today then usually. But im kinda a little worried. Any thoughts?

Great video man

I was looking at this 2001 dodge 2500 24valve and I drove it around and the checked for blow by and I put my hand over it no pressure didn’t budge the cap at all but had a bit of the white vapor smoke coming out so it’s normal???

A certain amount of blow-byis normal. Every engine, including new ones, have blow-by. Could you please tell me what digital gauge screen you are using here? Thanks.

What is the problem with the my truck if there is a lot of steam coming from the fill cap? I got a 99 7.3 with 140k miles

hi! the ccv is conected to the intake tube?

I’m just curious what motor oil and weight do you use for your 7.3

If smoke is coming out of the oil fill cap but doesn’t blow the cap off is it still okay to drive

Is anyone certain that the crankcase is sealed beyond just the oil cap? Isn't there a positive crankcase ventilation port where blowby would escape?

Is it actually being lifted or is the movement from the engine vibration? Vibration is obviously contributing to movement.

My 2000 f550 with 7.3 has 250k has nearly zero blow by and fully warmed up has less than your at starting .. so yours does have some blowby more than normal

If oil didn’t have water in it it would be a solid.

But what about the stock ccv? Doesn't it make all the tests pointless because the intake draws vacuum on the crankcase?

Is there a good way to check a e350 without getting into doghouse?

2020 mirror conversion?

So if it blows the ping pong ball off it's bad ? Or is it good ?

Tell me you don’t know anything about a 7.3 without telling me you don’t know anything about a 7.3. That’s not excessive blowby, that’s perfectly normal, you have to remember the compression on a diesel is extremely high vs a gas, and 7.3’s have more than a Cummins naturally.

I don’t see no blow by

Dang I need new batteries

So I’s the truck junk?

Lol you aren't looking for an older diesel. You are looking for a slightly used diesel.

This is why you don’t listen to every you tuber. Blow by is getting past the rings and pressurizes the crankcase.which can lead to many bad things.

That's nothing and completely normal..my 2001 f2shity 7.tree has over 700 thousand miles and has the exact same amount of crank case gas as yours.. it is moisture from the outside air which is sucked in by the air filter.....everyday of the year has different amounts of moisture in the air. Its science

The male truck identifies as SHE and HER!...wtf is going on w/ trucks nowadays ?😮😂