Leaking Gearbox Drain Plug (stripped threads) | FerrariChat

Leaking Gearbox Drain Plug (stripped threads)

Discussion in 'Boxers/TR/M' started by 302Tim, May 23, 2012.

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  1. 302Tim

    302Tim Formula 3

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    #1 302Tim, May 23, 2012
    Last edited by a moderator: Sep 7, 2017
    Threads on my 40K mile 88 TR gearbox drain plug (hole) are almost gone, can't get much torque on plug (plug threads are fine) and have been losing some fluid (photo 1). Photos 2 & 3 are for location reference only (not my cover). I've sealed the plug for now, successfully stopping leak and retaining the plug. Plan to permanently repair when the motor comes out, though appears with clutch/flywheel removed I could pull the cover/mount with motor still installed. Can also inspect diff carrier with cover off as well so double bonus :D :D

    Looking for repair options. I'm thinking either a heli-coil type thread insert or weld the hole shut (partially/fully) then re-drill/tap.

    Has anyone done a similar repair? If I go with thread insert does anyone know what size insert I would need? The plug OD measures 21.78mm (photo 4) and I could not accurately measure the hole ID.

    Baer, Timesert, Keysert and Heli-Coil all carry inserts with varying thread pitch repair kits so that option seems to be viable once I figure out the thread pitch in mm (it's ~18 TPI American).

    The welding option seems viable as well, I just need to locate a good machine shop that can weld aluminum--any pitfalls with this option (provided shop is competent)?

    Any suggestions or guidance is greatly appreciated.
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  2. Melvok

    Melvok F1 World Champ
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    #2 Melvok, May 23, 2012
    Try getting a new 22mm plug; this is always better than welding imo ... :)
     
  3. st@ven

    st@ven F1 Rookie

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    #3 st@ven, May 23, 2012
    it's not the thread on the plug that is the problem i think.
     
  4. fastradio

    fastradio F1 Rookie
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    #4 fastradio, May 23, 2012
    Last edited by a moderator: Sep 7, 2017
    Sure. No problem. The thread size/pitch is 22x1.5mm. I've done several repairs using the TimeSert inserts. We have both the kit and the inserts on hand. The factory sized plug will be retained, although I provide a new plug as part of the service. A few photos of the problem and solution.

    Best,
    David
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  5. Philwozza

    Philwozza Formula 3

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    #5 Philwozza, May 23, 2012
    Its an engine out job Jim unfortunately :( The clutch housing and flywheel needs to be removed to get the rear engine mount off. It can be done with the engine in if you are prepared to remove the studs from the crankcase, but that is itself a risky job also.
    I suggest that you degrease around the plug area and apply some clear silicone sealant for the time being. There should not be a large leak as this plug is located above (just) the oil fill level.

    HTH

    P
     
  6. Melvok

    Melvok F1 World Champ
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    #6 Melvok, May 23, 2012
    " The thread size/pitch is 22x1.5mm.2 " and " The plug OD measures 21.78mm " ... ...> get the right plug of 22 mm.2 !

    Or LocTite it !
     
  7. fastradio

    fastradio F1 Rookie
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    #7 fastradio, May 23, 2012
    He has the right sized plug...
     
  8. mtooze

    mtooze Karting

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    #8 mtooze, May 23, 2012
    Short term fix silicone or JB weld it...I have never trusted helicoil myself, but having not used one, I dont know why i dont trust them! I know they last very well in stripped spark plug holes...maybe one day I will have to use one!

    Welding is you best long term bet on the next engine out. I just did this myself on one of my airplane engines recently. If you dont have a TIG or dont trust your own welding skills, a decent machine shop can do it for you. It can be a bit of a witch sometimes on "old" aluminum...that oil loves loves to get in the pores and its comes right on out on welding and buggers up the weld.
     
  9. plip

    plip Formula Junior

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    #9 plip, May 23, 2012
    Hi

    have been using Helicoil since years on many different applications with excellent result. Last one on the stripped thread in the cam cover securing the stud for the vacuum pump on the left bank exhaust cam on my TR.
     
  10. 302Tim

    302Tim Formula 3

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    #10 302Tim, May 23, 2012
    Great responses, thanks guys for your inputs. To clarify, yes my original plug is good (steel threads) though I had thought of installing a new one that might have a bit more bite, but suspected that would only be another temporary fix. I actually lost ~1.25 pints of oil since I replaced the Redline in Oct (driven about 3K miles). more than I suspected, though I often park on an incline that puts the oil over the top of the plug, and when driving the fluid gets sprayed around quite a lot. Tried liquid teflon thread seal (didn't help), then Permatex "engine leak sealer" (an external spray, also didn't help). High-temp RTV was next on list but lacking that I reverted back to a former career and sealed the plug with a high-temp flexible aircraft integral fuel tank sealer (PRC 8802). Leak stopped (though may never get plug out).

    Phil thanks for the clarification on the removal, at this point I'll just wait until the motor comes out early next year, and likely go with the thread repair as outlined by fastradio.

    Looking at Davids repair, it appears a .5" longer plug would hit plenty of fresh (unused) threads and be the simpliest repair. Great excuse to buy that CNC machine and Bridgeport lathe I always wanted. Thats not gonna happen but an enterprising member might want to have some made. I'd readily pay $30-40 to solve that problem with a plug swap vs. heli-coil or welding. Perhaps not enough volume to bother but I've seen members here do some pretty incredible things from their shop/home.

    Anyway, thanks again guys, great help as always.
     
  11. Philwozza

    Philwozza Formula 3

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    #11 Philwozza, May 23, 2012
    Tim have you considered a Dowty seal? They seal without high torque settings so in a risky situation like yours this should work without stress on what is left of the thread and copper washer. I use them on all parts where a copper washer is the norm. They are a little more expensive but work every time without fail..

    HTH

    P
     
  12. fastradio

    fastradio F1 Rookie
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    #12 fastradio, May 23, 2012
    Tim,

    I have some new deeper plugs. They're considerably deeper than OE, with about 1/2" of total thread. I can later post a photo with dimensions, if you'd like. On the thread repair shown, I'm using the TimeSert system, where the insert is actually slightly recessed into the case. It is a very robust repair.
     
  13. Red Head Seeker

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    #13 Red Head Seeker, May 23, 2012
    Why not just drill it out & retap the hole to the next size plug?....Mark
     
  14. Philwozza

    Philwozza Formula 3

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    #14 Philwozza, May 23, 2012
    With a helicoil that is exactly what happens except you finish up with the same original size thread :)


    Helicoil, I wish I had invented that one: I could afford ALL the Ferraris in the world by now :D


    P
     
  15. Turbopanzer

    Turbopanzer F1 World Champ

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    #15 Turbopanzer, May 23, 2012
    May I offer a suggestion?
     
  16. 302Tim

    302Tim Formula 3

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    #16 302Tim, May 24, 2012
    Thanks David, not familiar with TimeSert but I really like this idea. If you sell the deeper plugs I'd definitely be interested, otherwise I don't have the resources (mainly talent :() to make my own.

    There isn't a "next sized plug" (at least OEM). Maybe a universal and/or industrial application, haven't dug that deep yet but thanks, another option

    Have heard of these but not familiar--I'll check them out, thanks for the tip. I know what you mean about the heli-coil system, could have made a few quid on a Velcro patent too, never seen so much on a car until I bought the TR ;)

    Please do....
     
  17. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #17 Steve Magnusson, May 24, 2012
    Last edited: May 24, 2012
    I don't have a dog in this hunt, but the timesert that David is proposing has some significant advantages IMO over either the helicoil or welding+retapping. Both the timesert and the helicoil have the advantage of providing a steel female thread interface -- which is a huge reliability advantage in this application (so no need to weld+retap just to have the same prior poor situation). However, the timesert is a 1-piece solid bushing; whereas, the helicoil is a wire threadform that can get distorted/mangled with use. The only reason to pick a helicoil over a timesert is that the helicoil has a smaller OD (for the same thread size ID) -- in this application, the boss has so much extra material and the plug has such a big diameter sealing head, that there is no reason not to use a timesert (and no compelling reason to use either of the other options neither of which are less work) -- JMO...

    David -- are you grinding the "head" off of the timesert prior to installation, or is it a "headless" type, or is the "head" still there in your photo?
     
  18. Turbopanzer

    Turbopanzer F1 World Champ

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    #18 Turbopanzer, May 24, 2012
    Will you be taking the cover out? Is so, the fix is very simple and inexpensive. It is called a T-Nut. It installs from the inside. Is pressed into place and once installed it lasts forever. If interested, PM me and I can show you a sketch of how to make one or have one made.
     
  19. hnyc

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    #19 hnyc, May 25, 2012
    Adding to Steve, I've used a Timesert on a motorcycle engine block where the threads were all but gone (aluminium block, steel plug, overeager mechanic). Once the insert is in, the same size bolt/plug can be used provided it's not stripped (and if it is, you just get a new one). It's been three months and there is no leaking and not even wetness around the area whatsoever. I don't know about other methods but I can say that this worked for me.
     
  20. fastradio

    fastradio F1 Rookie
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    #20 fastradio, May 27, 2012
    No, the TimeSert is not modified. It has a lip with rests against a lip which is cut by one of the installation tools. The lip of the insert sit slightly below or flush with the original casting. This is a perfect repair solution for stripped out drain plugs holes.
     

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