 Plenum Repair, Solder? Braze? Weld? Epoxy? Magic? |
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| ctc911ctc |
 Apr 15 2019, 02:35 PM
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#1
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Senior Member  Group: Members Posts: 1,124 Joined: 9-June 18 From: boston Member No.: 22,206 Region Association: North East States 
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I have been chasing a vacuum problem. Found 2 likely culprits so I started a new thread.
1. BOTH plenum support columns at the top are leaky. I just tried soldering and then brazing, both did not work. I am reluctant to weld because of the gage of the material and the skill of the welder......grin 2. The control shaft in the Throttle Body is leaking as well, is there any way to fix this without milling and new sleeves inserted? Also, as luck would have it, my son cleaned and painted the unit PRIOR to me having time to test it........ Thank you, CTC911CTC  |
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| 76-914 |
Apr 15 2019, 02:49 PM
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,700 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California
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Brazing is fine but might be easier to buy a known good one. The shaft needs to be redrilled with new bushings. The bushings are self lubricating and will be installed "in line" when done correctly. If that shaft were to bind when wide open you might be in for "the ride of your life".
I prefer the silicone rubber for those runners but you usually need to buy a 3' length at a diesel shop and it ain't cheap. It does take heat well and will out last the OEM sleeve. |
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| 914_teener |
Apr 15 2019, 02:49 PM
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#3
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914 Guru Group: Members Posts: 5,264 Joined: 31-August 08 From: So. Cal Member No.: 9,489 Region Association: Southern California |
JB weld for the plenum. Done.
For the TB. What Kent said. While you are there....how good is the throttle switch? Scored.....great? Is it clean? |
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| worn |
Apr 15 2019, 05:30 PM
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#4
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Winner of the Utah Twisted Joint Award Group: Members Posts: 3,470 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest
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QUOTE(ctc911ctc @ Apr 15 2019, 12:35 PM)  Also, as luck would have it, my son cleaned and painted the unit PRIOR to me having time to test it........ Luck has nothing to do with that sort of thing. I have had excellent results with silver containing filler rod when brazing reluctant steel. It comes with bright orange flux coat and is kinda spendy. Good luck. |
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| ctc911ctc |
Apr 15 2019, 06:57 PM
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#5
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Senior Member Group: Members Posts: 1,124 Joined: 9-June 18 From: boston Member No.: 22,206 Region Association: North East States
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*********UPDATE*******
Used fast set Marine Epoxy, chemically the same as JBWeld, after a few hours I tested the plenum and it held vacuum, also I pulled the control rod out of the Throttle body, put some white Lithium Grease on the shaft. Seems to hold..... (IMG:style_emoticons/default/beerchug.gif) After it sets firm (tomorrow) will try the pressure test. |
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| EdwardBlume |
Apr 15 2019, 07:10 PM
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#6
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914 Wizard Group: Members Posts: 12,338 Joined: 2-January 03 From: SLO Member No.: 81 Region Association: Central California
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Just a thought, but make sure you have or need to put the plastic bolt back on your accelerator stop. A common destroyer of plenums is not having the plastic bolt and flooring it a lot. Your plenum is compromised by the cable pulling the throttle open past where the throttle goes, tweaking the plenum.
Ask me how I know.... (IMG:style_emoticons/default/smile.gif) |
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| ctc911ctc |
Apr 15 2019, 08:24 PM
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#7
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Senior Member Group: Members Posts: 1,124 Joined: 9-June 18 From: boston Member No.: 22,206 Region Association: North East States
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Plastic Bolt? Accelerator Stop? HHHmmm, mine is a '74 2.0 - is there one on this plenum?
Do you mean the one on the floorboard? QUOTE(EdwardBlume @ Apr 15 2019, 07:10 PM) Just a thought, but make sure you have or need to put the plastic bolt back on your accelerator stop. A common destroyer of plenums is not having the plastic bolt and flooring it a lot. Your plenum is compromised by the cable pulling the throttle open past where the throttle goes, tweaking the plenum. Ask me how I know.... (IMG:style_emoticons/default/smile.gif) |
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| Mark Henry |
Apr 16 2019, 06:35 AM
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#8
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
QUOTE(ctc911ctc @ Apr 15 2019, 08:57 PM) *********UPDATE******* Used fast set Marine Epoxy, chemically the same as JBWeld, after a few hours I tested the plenum and it held vacuum, also I pulled the control rod out of the Throttle body, put some white Lithium Grease on the shaft. Seems to hold..... (IMG:style_emoticons/default/beerchug.gif) After it sets firm (tomorrow) will try the pressure test. I welded a surge tank to my VW bug gas tank, no matter how hard I tried I couldn't stop all the leaks. I used a quality marine epoxy and it sealed right up. Been in use about ten years now. They make fiberglass fuel tanks, I believe all underground tanks for gas stations are fiberglass. |
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| mgphoto |
Apr 16 2019, 03:33 PM
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#9
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"If there is a mistake it will find me" Group: Members Posts: 1,375 Joined: 1-April 09 From: Los Angeles, CA Member No.: 10,225 Region Association: Southern California |
I would find another, dangerous to weld or braze on the plenum because of residual fuel, just like a fuel tank.
Marine Tex is great stuff, used it to seal a vw gas tank. But it is not a permanent, vibration can loosen the material. |
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| dr914@autoatlanta.com |
Apr 16 2019, 04:04 PM
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#10
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914 Guru Group: Members Posts: 8,161 Joined: 3-January 07 From: atlanta georgia Member No.: 7,418 Region Association: None |
vacuum hose fitting for the aux air valve is pointing the wrong way
Have never seen the support tubes leaking before, if you are afraid of welding then epoxy they have some really good ones these days\ Tubes should be painted with Wurth zinc spray for the exact color and texture QUOTE(ctc911ctc @ Apr 15 2019, 01:35 PM) I have been chasing a vacuum problem. Found 2 likely culprits so I started a new thread. 1. BOTH plenum support columns at the top are leaky. I just tried soldering and then brazing, both did not work. I am reluctant to weld because of the gage of the material and the skill of the welder......grin 2. The control shaft in the Throttle Body is leaking as well, is there any way to fix this without milling and new sleeves inserted? Also, as luck would have it, my son cleaned and painted the unit PRIOR to me having time to test it........ Thank you, CTC911CTC |
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