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#1071077 - 06/14/21 04:48 PM EGR stem seal.  
Joined: May 2007
Posts: 5,008
Buick Runner Offline
10+ Year
Buick Runner  Offline
10+ Year
Member

Joined: May 2007
Posts: 5,008
Dharma station 1 the Hydra
I have been trying to find a stubborn vacuum leak. Smoked the engine and saw a little smoke coming out of the stem seal at the base of the EGR valve. The diaphragm is good and holds vacuum, its leaking from where the stem enters the base of the EGR valve. Searching online has not turned up much about this issue. Only thing I found was a Turbo Buick posting where a guy found he was losing boost through a leaking stem seal on his EGR valve and deleted it.

The stock EGR valves for L69s seems to be the negative backpressure type. The cutaway diagrams I have found don't list a seal but it appears there is one in the drawing. Using a inspection mirror there does appear to be a staked washer on the EGR valve that could be a seal retainer, similar to the staked washers for the stem seals on the airhorn for the accel pump and TPS plunger.


SBC powered 1987 Regal with TES headers, ZZ4 intake, ZZ4 PROM chip, mini starter, THM2004R, 2500 stall converter, 2040 cam, CCC system, and 3.73 posi rear.

2008 ex NPS P71 Crown Victoria, cop motor, cop shocks, cop brakes, and Jmod.

Never argue with an idiot.
They will just drag you down to their level and beat you with experience.
#1071092 - 06/15/21 01:52 AM Re: EGR stem seal. [Re: Buick Runner]  
Joined: Dec 1999
Posts: 11,891
86ttop Offline
20+ Year
86ttop  Offline
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Joined: Dec 1999
Posts: 11,891
Brooksville, Fl
to be certain of the positive or negative back pressure of your EGR valve, there will be a P or an N preceding the part number. I don't believe the stem seal can be serviced, good luck!


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#1071097 - 06/15/21 05:49 AM Re: EGR stem seal. [Re: Buick Runner]  
Joined: May 2007
Posts: 5,008
Buick Runner Offline
10+ Year
Buick Runner  Offline
10+ Year
Member

Joined: May 2007
Posts: 5,008
Dharma station 1 the Hydra
The valve has neither letter. The valve opens when I apply vacuum so its not a positive type EGR valve. My GM repair manual states most 305s have the negative type. Seems like the only fix is total replacement.

Last edited by Buick Runner; 06/15/21 05:54 AM.

SBC powered 1987 Regal with TES headers, ZZ4 intake, ZZ4 PROM chip, mini starter, THM2004R, 2500 stall converter, 2040 cam, CCC system, and 3.73 posi rear.

2008 ex NPS P71 Crown Victoria, cop motor, cop shocks, cop brakes, and Jmod.

Never argue with an idiot.
They will just drag you down to their level and beat you with experience.
#1071101 - 06/15/21 11:46 AM Re: EGR stem seal. [Re: Buick Runner]  
Joined: May 2019
Posts: 364
T5montecarlo Offline
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T5montecarlo  Offline
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Joined: May 2019
Posts: 364
Lederach, PA
I like to take things apart to see how they work. Try taking apart the original valve and see if there is a PN on the seal, then see if you can trace the manufacturer or replacement part number.

In the worst case, you have to replace the entire valve, which is the most likely outcome.

#1071632 - 08/16/21 03:56 AM Re: EGR stem seal. [Re: Buick Runner]  
Joined: May 2007
Posts: 5,008
Buick Runner Offline
10+ Year
Buick Runner  Offline
10+ Year
Member

Joined: May 2007
Posts: 5,008
Dharma station 1 the Hydra
I replaced the EGR with a GM NOS unit and its stem seal doesn't leak smoke.


SBC powered 1987 Regal with TES headers, ZZ4 intake, ZZ4 PROM chip, mini starter, THM2004R, 2500 stall converter, 2040 cam, CCC system, and 3.73 posi rear.

2008 ex NPS P71 Crown Victoria, cop motor, cop shocks, cop brakes, and Jmod.

Never argue with an idiot.
They will just drag you down to their level and beat you with experience.
#1071641 - 08/16/21 06:44 PM Re: EGR stem seal. [Re: Buick Runner]  
Joined: Dec 1999
Posts: 11,891
86ttop Offline
20+ Year
86ttop  Offline
20+ Year
Member

Joined: Dec 1999
Posts: 11,891
Brooksville, Fl
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Leo Paugh
It's not an attitude, it's just the way I am.
POW*MIA
You are not forgotten
If things improve with age, I must be approaching magnificent. thumbs

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