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Fuel drain plug leak

Discussion in '308/328' started by Irishman, Oct 27, 2019.

  1. Irishman

    Irishman F1 Rookie

    Oct 13, 2005
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    I have a leak at the fuel drain plug. I replaced the washer and at that time it appeared to me the surface of the drain opening was clean. Obviously, I missed something here as it's still leaking. Any suggestions on how to address it properly?

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  2. Steve Magnusson

    Steve Magnusson F1 World Champ
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    #2 Steve Magnusson, Oct 27, 2019
    Last edited: Oct 27, 2019
    Forgive me for being a nattering nabob of negativism, but that looks more like seepage from a crack in the weld area between the tube and the bung for the drain plug (and being under the thermal textured coating, it can be hidden). Putting a lot of torque on that drain plug (which is sometimes required) would put a lot of stress on the tube/weld in that area. Is it dripping directly from the drain plug joint or away to the left in your photo?
     
  3. thorn

    thorn Formula 3
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    It is an odd drip pattern...moving up and away from the plug?
     
  4. Irishman

    Irishman F1 Rookie

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    Hi Steve, no problem. I had to look up 'nattering' and 'nabob' : - ).

    It is what it is. I suspect your diagnosis is correct based on what I am seeing. It is indeed dripping from both the drain plug and away to the left as you can see in the photo.

    What is a bummer is that I cannot find a source for 106675, the pipe in question.

    Any suggestions as to how to to proceed?
     
  5. thorn

    thorn Formula 3
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    Would probably not be a difficult weld repair.
     
  6. Steve Magnusson

    Steve Magnusson F1 World Champ
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    You are probably just confirming that you are a lot younger than me ;) -- stolen from a famous (and accurate) quote from Spiro Agnew of all people.

    I think you've got to do some more investigation at a minimum (as thorn noted -- benzina usually doesn't flow up). Taking the tube off and pressure testing it, or digging some of the coating away at the highest point of the stain are maybe a couple of options. IMO, you've really got to be sure about where the fuel is getting out before deciding next action. Also agree with thorn that a weld repair shouldn't be too difficult with the pipe off the car if it is cracked -- duplicating the coating may be a challenge. Unless you can find another one from a F salvager.
     
  7. johnk...

    johnk... F1 Veteran
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    I bet you could come close to the texture with 3M Rocker Panel coating, and them maybe a light coat of wrinkle paint followed by aluminum spray paint for color.
     
  8. BigTex

    BigTex Seven Time F1 World Champ
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    I think the esteemed experts here are correct.

    Not the fitting leaking, it's a crack in the welding of the pipe.
    Underneath that spray crapola…:D :D
     
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  9. BigTex

    BigTex Seven Time F1 World Champ
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    There;s been some discussion of the fuel tank coating (this is similar) it's not the Rock Chip Spray Shurtz but it's similar.
     
  10. miketuason

    miketuason F1 World Champ
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    I think Steve is right, looks like seepage from from the welded area. I had this repaired in the past where I had the welding area reeled and build up more material which made it stronger thank the original welding. I suggest to do the same thing.
     
  11. johnk...

    johnk... F1 Veteran
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    I wouldn't be surprised if there is asbestos in that coating.
     
  12. kcabpilot

    kcabpilot Formula Junior

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    Leaks can be deceptive. It could be a slow seepage that remains unseen on the surface but follows gravity to the lowest point where it collects. The volatility of gasoline means it may evaporate faster than it can collect enough to actually drip. So in this case I'd examine the areas on either side up to the coupler hoses to be sure there is no evidence of fuel. Maybe wipe with a blue shop towel to see if you pick up any hint of fuel. It could be a very slow leak, barely perceptible but surface tension allows it to collect at the low point. The coupler hoses are the most likely points for a leak to occur.
     
  13. Irishman

    Irishman F1 Rookie

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    Thanks, that is good thinking. I replaced those hoses recently (though probably 5-7 years ago now). Can't tell from the photo I posted but the fuel really is isolated to the area around the drain. Those hoses and the rest of the pipe are bone dry.
     
  14. Irishman

    Irishman F1 Rookie

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    Do you recall what was involved in dealing with the coating around this pipe? And where you had that work done?
     
  15. conan

    conan Formula Junior

    Nov 13, 2011
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    Just for info in case someone wants to remove the pipe without fuel spillage and not removing the drain plug. I figured it would be fiddly to get the pipe out of the car without turning the pipe in many directions. I did the following steps:
    - Drained the fuel tank via the fuel pump hose, keeping the car at an angle towards the fuel pump side (lowest point at the fuel pump hose)
    - Put the car horizontal and remove the crossover hose
    - Siphoned out the fuel in the crossover pipe
     
  16. miketuason

    miketuason F1 World Champ
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    Kivin, sorry for the late reply. I don’t remember what coating was on the pipe but I remember cleaning the drain plug area and the welded area with the wire wheel and someone Reweld the and build up more aluminum on the welded area to stop the leak and made it stronger. The leak started when I tried to remove the plug to drain the fuel and by doing so, somewhere along the welded area crack. It has been five years now and has been dry, not one drop of fuel.
     
  17. Irishman

    Irishman F1 Rookie

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    Thanks, yes, I think that may be the irony in it for myself. A few years ago I replaced all the fuel hoses on the car, endeavoring to ensure no leak . I had to drain the fuel from the tanks to replace the hoses connected to this pipe. I had trouble getting the drain plug loose. I used an air gun on it. I suspect that was the cause of this leak. :(
     
  18. Irishman

    Irishman F1 Rookie

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    My approach to a solution was to find another pipe. For about $75 I got a used pipe from GT Car Parts. Seemed much cheaper to me than having someone fix my broken pipe. Problem is I *still* have a leak :(. So I'm wondering...

    1) What is the proper torque value for this fastener (ie it's loose)?
    2) Could I have not cleaned the mating surfaces properly (I used scotch brite)?
    3) Could the crush washer be bad (I used a new one)?
    4) Other???

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  19. Steve Magnusson

    Steve Magnusson F1 World Champ
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    The crush washer needs to be new and unused (i.e., fully annealed and very soft). Once it is "crushed", it gets very hard (a process called strain-hardening) - they can't be reused unless they are re-annealed.
     
  20. Irishman

    Irishman F1 Rookie

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    Thanks, Steve, so if I start over with a new crush washer, what do you recommend as the tightening torque?
     
  21. 2NA

    2NA F1 World Champ
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    I've had one of those pipes break at the weld. Fortunately most of the fuel was out already and I was prepared for the flood.
     
  22. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Enough so it doesn't leak? ;)

    Seriously, this is more of a feel thing sensing the rate of change of the angle rotated vs the torque applied IMO -- i.e., as the "stiffness" of the washer increases during the crushing process, the additional torque needed to rotate the plug a little more just gets higher and higher. Can't say that I've ever seen a torque spec for this particular plug in the F documentation, but the female threads being aluminum (and the welded joint taking the stress) I wouldn't go very high -- maybe 20~25 ft-lb? If anyone has another idea/suggestion/reference, please post.
     
  23. smg2

    smg2 F1 Veteran
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    Sounds right to me, I'd also suggest as a last resort, permatex #3 aviation sealant on the threads. Had a 308 that weeped fuel regardless of copper washer or tq. The sealant worked.
    Given that the pipe is also fitted with rubber hoses at both ends, it's worth making sure the weep isn't coming from one of them. I've also replaced a couple of those cross over pipes due to cracks from that drain plug.
     
  24. waymar

    waymar Formula Junior

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    FWIW my crush washer OD was about the diameter of the hex and made from aluminum. I actually roughed it up a bit and reused it about 12 yrs ago. My winter chassis check showed no leakage.... just saying...
     
  25. Irishman

    Irishman F1 Rookie

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    Thanks, guys. Looking dry now. Confirmed with a paper towel after sitting overnight with gas in the tank.

    I let it drain overnight. Next day I installed the drain plug using the recommended Permatex #3 aviation sealant on the threads and a new crush washer. I'm certain I went beyond 25 ft-lbs. Probably more like 35 ft-lbs. Let it sit for a week before adding gas.

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