Hey guys, I know that pretty much every 7.3 ever made has some blow by to a degree. I checked mine out today, and a little more smoke than I was hoping for was coming out of the oil fill neck. It doesn't blow the oil cap off, and I can't feel any pressure blowing out of the filler neck, but it's still a little more than I'm comfortable with. Not quite sure how to upload the video, so if someone could help with that, that'd be great.

 

Smoke is normal. My experience has been that it's white and really stinky.

 

Smoke isn't blowby. This is a high compression engine. Pressure is blowby.

I've tried multiple different oil on my 7.3 over the last half a million miles or so. My experience is, different oils smoke different amounts. Different miles on the same oil produce a different amout of smoke. Current weather conditions can also affect the smoke. Different oils also have different smells to them that also change as they get more miles on them.

I don't remember which oil it was, but back around 250k miles I had a whole lot of smoke from the fill tube. 310k miles later the truck is still running strong and Blackstone labs can't find anything wrong on the UOA's still.

 

Also remember that oil neck blowby isn't all that reliable when checking for bad rings/cylinders. I had almost no blowby (wouldn't move an oil cap turned upside down) and 3 cylinders were dead. Wouldn't pull a little boat up a hill anymore.

The smoke though, don't sweat it. They all puff-puff-puff like a choo choo train.

 

And what was the cause of the death that it didn't create blow-by?

 

I'll never know. It happened with the PO. I drove it a year and repaired the heck out of everything else. It never had much power, but being my first 7.3 I didn't know that. Seemed similar to a high geared small V8 when i popped the clutch. One day it couldn't pull itself and my boat up a small hill and I finally put it in the shop. 3 cylinders were dead.

 

Are you sure it wasnt the valves no sitting right? Because bad compression on any engine will emmit blow by specially on diesel engines.

 

They scoped it. Looked like a warzone.