C7 Blow By

[GCecchetto]

For you folks with C7 powered trucks, I'm curious how much blow by you see out the breather. Thanks

 

[GeneralDisorder]

Lots unless you run them two quarts low. It will spit out what it doesn't want. CAT redesigned the breather to be more like the 3126 to avoid it but it doesn't fit under our cab.

The military guys all know about it and just run them halfway between the low and full which is 2 quarts. That's also what I preach and practice personally.

 

[GCecchetto]

Lots unless you run them two quarts low. It will spit out what it doesn't want. CAT redesigned the breather to be more like the 3126 to avoid it but it doesn't fit under our cab.

The military guys all know about it and just run them halfway between the low and full which is 2 quarts. That's also what I preach and practice personally.

Thanks, that's where my oil level is, but I was referring to gases coming out, not oil.

 

[AKPacker]

For you folks with C7 powered trucks, I'm curious how much blow by you see out the breather. Thanks

Mine smokes a good bit out of the breather on cold starts if it has been sitting for a while. Not nearly as noticeable during warmer weather and if it is driven more frequently.

 

[fuzzytoaster]

I've got 4 A1R trucks and had 11 over the years. They will all have some degree of blowby, it's a medium duty diesel so it's inherent that it will have some. If you can't visibly see the blowby that's a good sign. If it's blowing the cap/bung out that's a bad sign. Anywhere in-between is fine as long as fluids are good, performance is good, and you are satisfied with the engine as it is.

 

[Skyhawk13205]

If you want to big deal it you can have Cat do the blow by test with a special meter that is attached to the breather to get a specific CFM for acceptable blow by.

 

[GeneralDisorder]

I haven't noticed anything significant from mine unless it's over filled. Once it finds the level it likes (assuming over filled) nothing much is evident from the breather. Maybe a little vapor.....

I'll have to throw a go-pro down there and film it I guess to really compare since it's a pretty subjective thing to discuss without a frame of reference. It's a breather so I don't expect the inside of the hose to be dry for example.....

I do feel like the amount of breather activity has calmed down on mine - obviously in part from running the engine two quarts lower than full to avoid the chassis lube option.

I also feel like my engine has smoothed out significantly since I got my truck. 2,750 miles in 2021. About 28k miles today. The steering wheel vibrations are almost gone now.

 

[GCecchetto]

I have visible vapor coming from mine, most noticeable when the light is just right. My motor could still be wearing in, just coming up on 10k miles. For a medium duty diesel that’s not much. In the owners manuals for the Cummins powered rams it says not to use synthetic oils at less than 10K miles.

Anyway truck runs like a top, so not really worried about it. Next time I’m driving it, I’ll take a short video of the breather and post it.

 

[GCecchetto]

Well, guess I can't attach a video.

 

[Ronmar]

You have to upload it someplace like Youtube and link to it…

 

[GeneralDisorder]

I took a video of mine and the file was corrupted. Have to try again. Don't use my go-pro that often.

 

[GCecchetto]

You have to upload it someplace like Youtube and link to it…

Yes, I realized that when trying to attach it. Didn't really want to mess with that but did anyway. Even though it has been uploaded to youtube, when I try to insert the link it says I can't.

 

[GCecchetto]

Okay, trying another way.

https://youtube.com/shorts/Dy76P6kncmw?si=IpbSM4OmJadDt6bS

 

[Ronmar]

You need to make your video public on YT…

 

[GCecchetto]

You need to make your video public on YT…

Done. I thought since I shared it here, it would allow people accessing here to see it.

 

[GCecchetto]

I took a video of mine and the file was corrupted. Have to try again. Don't use my go-pro that often.

Phone is the easiest way.

 

[AKPacker]

@GCecchetto here's mine after a cold start around 40°F: https://youtube.com/shorts/zbHlE_uyk-4?feature=share

 

[GCecchetto]

@GCecchetto here's mine after a cold start around 40°F: https://youtube.com/shorts/zbHlE_uyk-4?feature=share

Cool, thanks. Looks just like mine.

 

[MatthewWBailey]

Lots unless you run them two quarts low. It will spit out what it doesn't want. CAT redesigned the breather to be more like the 3126 to avoid it but it doesn't fit under our cab.

The military guys all know about it and just run them halfway between the low and full which is 2 quarts. That's also what I preach and practice personally.

On this Breather issue, can the existing breather tube be routed into a remote tank that's then outfitted with the proper cat breather? Should it be a stainless tank or just anything that will fit that tall Cat breather?

Mine is making a mess under there even when I'm 2qts low. I got some blow by vapor, given the wear on this 3126.

 

[Ronmar]

i routed my breather line outside the frame as mine had made quite a mess of the plumbing and wiring inside the drivers frame rail with supposedly only 8500MI on the truck... The larger the flow the larger the surface area/volume needed to condense/settle the vapor out of the stream. it probably doesn't matter what the material is as it is not super high temp, just needs a routing that will allow it some opportunity to collect the liquid and a way to drain it off... An old A0 air dryer canister might work well with some modifications to direct the flow properly inside to make best use of the heat sync casing.

I think I would leave the cat "breather" in place on the engine as it is probably separating out some oil and keeping it in the engine, and run its output thru the "catch can"...