Pressurized engine

[marek4792]

(02-06-2026 )Scoot5869 Wrote:  Any idea what I need do a plug size wise? Save from me stopping at 20 places lol

Your local stealership/ cummins shop should have it. If the plugs are the same size across the engine platforms Part # 3678845 and oring #3678846 should work, but incase take the original piece with you.

[Scoot5869]

Ok i rigged up a plug a pressurized the system again. I am still getting air coming out of the hole in the crankcase filter.
Is this a sign the head is going bad? It doesn’t use any coolant engine was rebuilt 200k ago all Cummins part nothing aftermarket.
The egr system has been removed and correctly blocked off and I installed a hose in place of the cooler

[marek4792]

Not necessarily. The crankcase isn't 100% air tight. To rule out the head you'd have to remove the rocker shafts so all the valves are closed and test. But even then 20 psi boost you'd should hear it pissing air/exhaust somewhere.. Kinda starting to think you may have a sensor in range failure causing low boost and not necessarily a mechanical issue...

[Scoot5869]

Ok. What sensor should I be looking at I think I’ve replaced them all in the last two years.
Idk how to view/monitor things on Ct if any of that would help in see what’s going on

[marek4792]

Only insite. Look in live data and the engine state monitor. If it's derating it should tell you why. 2 years is kinda awhile for your EGR tuneup sensors and should be replaced yearly and passage cleaned out. Fuel pressure sensor too if it hasn't yet..

[Scoot5869]

I didn’t see anything the other day when I ran a load and had it hooked up. Fuel
Sensor were replaced 2 years ago when i did ifsm just checked the exhaust pressure tube when I had manifold off an cleaned that sensor imap was done two years ago I don’t run a lot of miles in a year local work maybe 20-30k. Cam and crank sensors were just replaced. lol I said all the egr stuff is gone and the truck has no exhaust.
The turbo actuator came with the reman turbo from hd turbo so it’s just over a year old

[Scoot5869]

Wanted to do an update even though it’s been a while things got busy.
After checking everything that was suggested I ended up checking the injectors as well I had two injectors one on each bank leaking. Replaced those failed after two years by the way. Truck ran much better but still Had issue ended up having a bad metering actuator as well replaced it and truck runs great. I rarely hit 30psi but the truck has the power it used to and my mileage is back to where it should be.
All my injectors and actuators were replaced at the same
Time stuff just doesn’t last any more. Oh and the actuator went up 200$ from when I replaced them the first time 900 some bucks now

[Rawze]

thanks for the follow up.