Boost Leak at back of engine..?

SubliminalME · May 18, 2021

I made a make-shift boost leak tester today out of PVC, and charged the system to 10 PSI.

Found multiple loose boots on the IC piping. Fixed via soapy water test.

I sprayed all around the AFC and the tubes from the intake and that all seems good.

I juiced it up to 15 psi. I can hear air moving behind the fuel filter/engine?

I juiced it up to 20 PSI. Boost gauge stayed at 15 psi and I just heard what sounded like air moving (not a hiss, but air movement) again behind the fuel filter/ housing/engine/firewall area.

What the heck? Do I need to turn my engine a bit? Could it just be a valve open or something? No air seemed to be coming out of the tailpipe...although I'm not sure if I'd notice anyway. If it was an intake valve, could it be recirculating?

Not sure where to go next. Blew the cap off at 20psi and it scared the heck out of me. Ha

Oldgraig64 · May 18, 2021

Did you check for a boost leak at the intake shelf gasket??

2002CTD · May 18, 2021

x2 for intake plenum gasket.

ekvhekvh · May 18, 2021

Intake plenum gasket should show with soapy water. If you stop the motor at a point where a valve is open, it’s going to allow air through. If it’s in the overlap where both are open it will let lots through. If the rings are weak or gaps are aligned you’ll lose some. You could be hearing it coming out the tappet cover vent. Try rotating the motor a bit to see if it reduces or stops. Then use soapy water for bubbles.

SubliminalME · May 19, 2021

Thanks guys. I rotated the motor and it definitely changed, so I believe it was just going out the valves.

I'm still at a loss though...I cannot get this truck to go over 15 PSI...even when I put 20 PSI into the turbo with my air compressor.

And yes, I did spray soapy water all around the intake horn above the p pump and saw no air bubbles.

jimduchek · May 19, 2021

SubliminalME said:
And yes, I did spray soapy water all around the intake horn above the p pump and saw no air bubbles.

Not just the intake horn. The intake manifold is cast into the head itself, but there is a plate on top of it (it's what the grid heaters/intake horn bolt to) -- goes all the way back to #6 and could be hard to see bubbles way back there. See: CC-TR12V Dodge 5.9L Cummins Tunnel Ram 12V Intake Plenum Cover

(No, it's not stock, literally just the first thing that came up in a search and it illustrates it well enough).

Boost Leak at back of engine..?

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