EGR vent port leak.

[Rusty Klunker]

Hey, all. New to the group and hoping there are people on here with some Duramax technical experience who can answer my question.

Backstory: LBZ Duramax. Loss off power and excessive smoke. It’s has been determined by me and 2 separate shops that it is a boost leak. The problem is where it is leaking. The EGR valve. There appears to be what I have determined as a vent port on the bottom. I have attached a picture for reference. I have now replaced the EGR 3 separate times, first and third time with OEM. Second with aftermarket. All 3 times a major boost leak from the port on the underside of the EGR. Right now my temporary solution is block off plates at the EGR but this is not permanent as I live in an emissions county.

My question is: Is this normal for LBZ EGR valves? If so what is the normal operation of the port on the bottom? 2 independent shops and the dealer have told me this is not normal, but they keep just wanting to throw new Egr valves at it. Has anyone had a similar experience? I’ve looked through a few forums and YouTube videos, but not much info on this particular EGR leak.

To add, I have tried various combinations of Egr valves and coolers both OEM and after market. As well as an after market and factory tune. Exhaust is PPE manifolds, up pipes and down pipe to a 4” exhaust with a cat.

 

[2004LB7]

First time I've heard of it. Especially three times on the same vehicle

Maybe you have excessive exhaust back pressure. Clogged cat?

 

[Rusty Klunker]

First time I've heard of it. Especially three times on the same vehicle

Maybe you have excessive exhaust back pressure. Clogged cat?

Maybe, cat is only 2 years old. This still wouldn’t explain why it is leaking under a boost test. I can pull the cat off pretty easy though so I’ll check it out.

Edit: Pulled the cat and it looks fine.

 

[Bdsankey]

Maybe, cat is only 2 years old. This still wouldn’t explain why it is leaking under a boost test. I can pull the cat off pretty easy though so I’ll check it out.

Edit: Pulled the cat and it looks fine.

So you're saying when you apply 30-40psi to the CAC plumbing you can audibly hear/feel/see it leaking out of that port?

 

[Rusty Klunker]

So you're saying when you apply 30-40psi to the CAC plumbing you can audibly hear/feel/see it leaking out of that port?

Correct, it won’t hold any pressure. The leak is very noticeable. I’ve done a boost and smoke test from the turbo faceplate.

 

[Bdsankey]

And this is on all the valves with key off?

Is the EGR plugged in I assume? If so, does it do the same unplugged?

 

[Rusty Klunker]

And this is on all the valves with key off?

Is the EGR plugged in I assume? If so, does it do the same unplugged?

Plugged in, unplugged, key off, key on. Leaks no matter what. Which is why I’ve thrown 3 valves at it. Seems to be the logical solution that it’s a mechanical failure either with the valve seal failing or an issue with the port. But I haven’t gotten an answer as to what the function of the port actually is. I originally thought maybe there was a relearn cycle or some sort of calibration needed for the new valve, but I’ve been told it should be plug and play by the shops I’ve had look at it.

 

[Ron Nielson]

From the attachment
When the ignition is turned ON, the ECM will drive the EGR motor worm gear out with just enough force to touch
the EGR valve stem. The ECM will do this 3 times in quick succession. This action determines the minimum
closed position of the valve and only happens once per ignition cycle. If the valve is prevented from closing all of
the way after the minimum closed position is learned, the scan tool EGR Position parameter will not reflect this
position until the next ignition cycle. The EGR motor worm gear is not connected to the EGR valve stem and can
only push the valve open. The valve is returned to the closed position by a return spring.

 

[Rusty Klunker]

Thanks, but that doesn’t really answer my question about the function of the port on the bottom. Is there a condition it should “vent” boost or is it a leak? With the Egr open under boost it would leak past the valve seats and into the exhaust system, but with the Egr closed it leaks past the stem, out the port and into the motor/return spring. (See pic of soot on spring motor)

 

[Ron Nielson]

Slightly different info, but showing how the valves seat in the EGR.. Motor protrudes too far to permit closing?? I'm wondering if your valve ever actually fully closes?? Can you monitor the EGR position with your scanner?

 

[SoCalMike]

Have you tried to remove the EGR motor and pressure test for boost leaks? EGR motor may be bad and not resetting, pushing the valve open slightly.

 

[Rusty Klunker]

If the valve was open slightly it wouldn’t be leaking out the port on the bottom, it would leak through into the Egr cooler and continue out the exhaust. I have data logged every Egr and under boost conditions it holds a 0% position (closed) but won’t get close to target boost.

The problem isn’t it leaking past the valve seats. It’s an external leak out the port on the bottom of the valve. Meaning it’s leaking past the valve stem towards the motor. And I’m just trying to figure out if this port has an actual function. It leaks out this port no matter the condition, I’ve tried boost testing right after install before start up, after start up, after setting readiness, I’ve bench tested 2 of the 3 egrs I’ve bought, with and without the motor and every time the same leak. I can put my finger over the port and stop the leak until it builds enough pressure to leak past my finger.

I’m leaning towards them just being bad parts, but I can’t wrap my head around having 3 new valves all be bad. And my wallet is definitely feeling it ?

 

[Bdsankey]

Are these genuine GM valves or aftermarket units?

 

[Rusty Klunker]

Are these genuine GM valves or aftermarket units?

2 have been GM, 1 was after market.

 

[Bdsankey]

Something isn't adding up. I can rip the valve and cooler off my parts truck to send to you for testing.

I personally have never seen the issue you're describing.