Fix for weeping EGR valve

MOGolf

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See the thread in the A4 maintenance section.
http://forums.tdiclub.com/showthread.php?t=128298

The same procedure could be used on the A3/B4 intake manifold with non-removable EGR, though I haven't tried it. Possibly cheaper than replacing the entire manifold because of the oil blowing out of the EGR vent holes.
 

Lug_Nut

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K.i.s.s.

I added a drain tube to channel this unsightly stain forming annoyance weep into the "puck" on top of the valve cover.
Occam strikes again
 

Toronto_Vento

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Interesting project. Like Alco stated in the thread, not so easy to get at the A3/B4 EGR, but would be interesting if someone could actually dissassemble the EGR and fix the leak totally.
 

paramedick

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Give me a chance. Mine crapped out. Temporarily have a later model A3 intake in place. Just gotta clean the stock B4 intake first.
 

Rickstah

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I've been having this problem with mine, spitting out oil, and it has been smoking badly since it started, so I figured boost leak. I thought this was just a seal for the egr shaft or something, so last weekend I just sealed it up since the egr setting had been set via Vagcom. This stopped the leak, but the next morning when I started it up it became evident it had gone into limp mode, the turbo would start to spool up to about 5-6 pounds then it would just die, and I was left with nothing. Vagcome showed the 575 code. I searched for leaks for hours, not finding any leak. After I cleared the code it ran as before, just find, still lots of smoke. I drove it for two days out to NM this past weekend, ran the dog out of it, it performed fine. I went from Austin to Roswell, NM, elevation 3600 feet, spent the night there, several ignition cycles. Got to Albuquerque, elevation 6250' where I was staying, shut it down. The next morning, limp mode again. I was supposed to pull a trailer back to OKC, but it certainly wasn't going to happen with a limp mode A3 and mountains, so I went to VW there, expecting them to find the 575 code and clear it out and I would be on my way...there were no codes!! Clear...they had no idea where to start looking, either. I looked again for any leaks, couldn't find anything...the n75 "sounds" like it is working.

The only factor here is sealing up that weep hole as far as I can tell, but having no codes show up, that is puzzling me no end. Why would sealing that up cause a problem, unless it also served some purpose as an opening to ambient pressure or something? (scratching head)
 

compu_85

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That hole is the vent for the EGR. I guess the EGR could get suctioned open if it were sealed really good?

-J
 

MOGolf

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Yes, that hole keeps one side of the diaphram at atmospheric pressure. This fix re-seals the shaft, not plug the hole.
 

redmondjp

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Rickstah said:
. . . The only factor here is sealing up that weep hole as far as I can tell, but having no codes show up, that is puzzling me no end. Why would sealing that up cause a problem, unless it also served some purpose as an opening to ambient pressure or something? (scratching head)
Read this other post regarding an oil leak from the vent hole:

http://forums.tdiclub.com/showthread.php?t=125395

Plugging this hole could cause the EGR valve to come open under high-boost conditions (boost pressure leaks into the atmospheric-pressure side of the EGR valve diaphram past the leaky stem seal--if the vent hole is plugged, then this pressure builds up and works against the diaphram, causing the valve to open).

Try temporarily reopening the vent hole and drive it for a couple of weeks to see if the problem goes away.
 

Rickstah

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(laughing helplessly) chipped it open last night and it miraculously healed itself :p ...oh well, it weren't too bad a ride in the U-haul, snicker...back to square one, now, with the leaking weep hole. Thanks for the info.
 

whitedog

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Rickstah, the key here is pressure differential. A low pressure (Vacuum) on one side and atmospheric pressure on the other side causeing the diaphram to be pushed to one side. Without the higher pressure able to get in on the one side, there can be no movement. Add in that once it is pushed all the way to one side, there is no way for it to move back and displace the air on the now sealed side.
 

Rickstah

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I agree, Whitedog, and if I had made the connection that it was to equalize pressure I wouldn't have closed it up. I have always thought the term "weep hole" meant a telltale of sorts to show a leak somewhere that wouldn't be easily spotted, guess we shouldn't call it that anymore, at least with guys like me around :)...I'll call it an APEO...atmospheric pressure equalization orifice :D

Lug_Nut, did you just drill a hole into the puck then jam the hose into both holes and then seal around both openings?

What I want to know is this...if that is an opening for something to sense ambient pressure, how does boost being forced out of it adversely affect the egr? Will it perform its function at the wrong time? Perhaps it should be disabled anyway? I am also wondering if the amount of boost that comes out causes some consternation to the ecu?
 

Lug_Nut

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Yes, I created a new opening in the puck with a slightly smaller drill bit than the OD of the vinyl tube I used.
The EGR vent is just that, a vent to allow the inevitable fluid (air and/or oil) migrating past the actuator seal to be vented to atmospheric pressure. Remember that no seal against a moving object is perfect. There is always some rate of leakage. The rate of leakage will increase as the object and seal erode from friction against each other.
The important consideration is the rate of boost pressure leakage past the shaft and seal into the diaphram chamber, compared to the rate of leakage of that migrated pressure in the diaphram champer out to atmosphere. As long as the rate of boost leaking into the chamber is less than the rate of leakage out to atmosphere, the diaphram will continue to operate correctly.
 

Rickstah

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Very well put...I think :D

It probably makes taking the puck off a little more awkward? Anyway, the oil mess is making me crazy, have to do something, thanks for the info.
 

redmondjp

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Lug_Nut said:
Yes, I created a new opening in the puck with a slightly smaller drill bit than the OD of the vinyl tube I used.
The EGR vent is just that, a vent to allow the inevitable fluid (air and/or oil) migrating past the actuator seal to be vented to atmospheric pressure. Remember that no seal against a moving object is perfect. There is always some rate of leakage. The rate of leakage will increase as the object and seal erode from friction against each other.
The important consideration is the rate of boost pressure leakage past the shaft and seal into the diaphram chamber, compared to the rate of leakage of that migrated pressure in the diaphram champer out to atmosphere. As long as the rate of boost leaking into the chamber is less than the rate of leakage out to atmosphere, the diaphram will continue to operate correctly.
You are correct, but the reason you give for the vent is a secondary one.

Atmospheric pressure is what causes the EGR valve to open (when the pressure is lowered on the opposite side of the diaphram by applying a vacuum to it), and the spring inside the valve chamber causes the valve to close when the vacuum is removed. There has to be an opening there to allow atmospheric pressure to reach one side of the diaphram. That's the primary reason for the 'vent.'

Sorry if I'm splitting hairs again, but even if the EGR shaft seal was perfect and allowed no leakage past it, the vent hole would still be necessary.
 

whitedog

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redmondjp said:
You are correct, but the reason you give for the vent is a secondary one.

Atmospheric pressure is what causes the EGR valve to open (when the pressure is lowered on the opposite side of the diaphram by applying a vacuum to it), and the spring inside the valve chamber causes the valve to close when the vacuum is removed. There has to be an opening there to allow atmospheric pressure to reach one side of the diaphram. That's the primary reason for the 'vent.'

Sorry if I'm splitting hairs again, but even if the EGR shaft seal was perfect and allowed no leakage past it, the vent hole would still be necessary.
Pressure differential as noted above, just worded differently.
 

Lug_Nut

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Temper Tantrum

redmondjp said:
You are correct, but the reason you give for the vent is a secondary one.

Atmospheric pressure is what causes the EGR valve to open (when the pressure is lowered on the opposite side of the diaphram by applying a vacuum to it), and the spring inside the valve chamber causes the valve to close when the vacuum is removed. There has to be an opening there to allow atmospheric pressure to reach one side of the diaphram. That's the primary reason for the 'vent.'

Sorry if I'm splitting hairs again, but even if the EGR shaft seal was perfect and allowed no leakage past it, the vent hole would still be necessary.
If the vent port is blocked completely then the vacuum pump provided partial atmospheric pressure (not vacuum, just lower than atmospheric, to further split hairs) will still draw the diaphram upwards until the lowering pressure below the diaphram equals the pump generated reduced pressure, plus the spring force, from above. The EGR valve will still open, vent hole plugged or not.
Presume 14 psi atmospheric pressure on both sides plus a 2 psi equivalent spring on top. Pumping air out of the upper side down to 10 psi will draw the diaphram upward until the pressure below is at 12 psi.
I can hold my nose, close my lips and still puff my cheeks out until I turn blue.:(
 

whitedog

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Lug_Nut said:
If the vent port is blocked completely then the vacuum pump provided partial atmospheric pressure (not vacuum, just lower than atmospheric, to further split hairs) will still draw the diaphram upwards until the lowering pressure below the diaphram equals the pump generated reduced pressure, plus the spring force, from above. The EGR valve will still open, vent hole plugged or not.
Presume 14 psi atmospheric pressure on both sides plus a 2 psi equivalent spring on top. Pumping air out of the upper side down to 10 psi will draw the diaphram upward until the pressure below is at 12 psi.
I can hold my nose, close my lips and still puff my cheeks out until I turn blue.:(
Ahh, but Lugnut, as the diaphragm moves, the volume on the vented side will increase, correct? If no air can get in what happens on the vented side as that diaphragm is moved? That's right, the pressure lowers since there is now the same amount of air in a larger volume chamber. It may move, but it will be slowly and not as far. Then what happens when the vacuum is removed form the other side? While it was held there, there was a tiny bit of leakage along this shaft spoken of earlier, so now the amount of air on the vented side is where it is supposed to be then everything is trying to move back the other way, compressing that extra air since the vent is closed. This would result in difficult movement.
 

Rickstah

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You guys are killin me :p...and who said anything about a tiny amount of leakage...it gets pretty oily if I push the boost up, and this fluttering noise makes me think the boost leak is getting worse. So...the vent hole is primarily for the egr vale to function properly...if the egr were disabled or removed (epsilonian?) then I could close up that hole to prevent boost/oil leak and it wouldn't send a limp mode code (which doesn't show up on the ecu)?
 

whitedog

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Remove the EGR and plug the hole then do what ever you need to keep Big Brother happy. Then drive that sukka!
 

Rickstah

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Hmm, I do recall seeing an intake with the integral egr that was removed and it was welded shut or something...need to dig that up.
 

Lug_Nut

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redmondjp said:
but even if the EGR shaft seal was perfect and allowed no leakage past it, the vent hole would still be necessary.
It was to this postulation that I was responding. The imagined scenario, purely theoretical, is that the seal is ultimately perfect and no other source of air in the lower section of the diaphram chamber exists, i.e. no leak past the seal.
What would happen with this fictitious set of limits?
redmondjp claims that the vent is mandatory with the implication that the diaphram wouldn't move without a vent.
Both Ed Boyle and I refute that assertion.
Remember Ed? Boyle's law on gasses?

A perfect seal as redmond wishes would not allow boost pressure migration up the EGR shaft into the lower diaphram chamber. Removal of the less than atmospheric pressure developed by the vacuum pump would restore atmospheric pressure to the top of the chamber. The lower pressure on the lower portion of the diaphram (remember the perfect seal with no leak to raise the pressure on the bottom side) would 'suck' the diaphram back down with the same velocity regardless.

All moot issues. There is no perfect shaft seal. The vent exists to prevent boost pressure that leaks past the shaft seal from pressurizing the lower part of the diaphram chamber. As the seal and shaft wear there is greater clearance to allow larger oil molecules past in addition to the air. The tube guide of the air / oil mist to the intake side of the turbo does absolutely nothing to stanch the oil migration. It merely keeps the stain off the intake.
 
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