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Oil tank drain plug thread size?

Discussion in 'Boxers/TR/M' started by c4b4the04, Feb 10, 2020.

  1. c4b4the04

    c4b4the04 Karting

    Jun 9, 2017
    94
    Northern Virginia
    Full Name:
    Cassidy
    For some reason, M14 1.50 is coming to mind...

    My ham-handed assistant "helped" me change oil the week I bought the car (and dropped the motor for timing belts...it was a crazy first week in the F-car world!). He stripped the threads as he used a 1/2 inch BREAKER bar to remove the plug. No it wasn't frozen, yes I was upset, no I didn't consider hiding the body).

    Anyway, fast forward to now and I will drop the bottom section of the tank, install a new screen and gasket and retap that with a Helicoil. Need to order the right size Helicoil kit though, as I don't have any that large.

    Thanks in advance. FWIW, I "solved" the issue at the time by using a tap and chased the threads further into the tank, then used a spot of blue loctite and a fiber gasket. It hasn't dripped a drop but it needs to be properly done IMHO.


    Car is an early 88 TR.

    Thank you,
    Cassidy
     
  2. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
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    In defense of your helper It makes no difference what size tool he used, you don't damage threads removing a plug. Whoever installed it did it. Its 14 x 1.5. Best to remove the oil tank bottom cover to repair. If not drilled and helicoiled perfectly straight it will never stop leaking.

    People do that so often to TR oil tanks I keep an exchange part on the shelf, helicoiled and ready to install. Never found reason to replace the screen.
     
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  3. c4b4the04

    c4b4the04 Karting

    Jun 9, 2017
    94
    Northern Virginia
    Full Name:
    Cassidy

    Good to know on the screen. Thank you, I just assumed while I was in there...

    As for my heavy-handed pal, I truly think it was a sideways tug that did it. Could be wrong, but he broke several things in the process, ones I'd like to think I could have avoided but you are right, could be from beforehand too.

    Thank you. Good to know and I agree on pulling the cover. Any idea what size those AN-type fittings are on the oil line? I don't have all of the large metric wrenches and will borrow the few I need.

    Cassidy
     
  4. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
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    By the time they are that big, metric or inch size makes no difference. Even a big crescent wrench, they are not very tight.

    The head of the plug is so shallow there is no way to put meaningful side load on the plug. Your helper did nothing wrong, the last installer did.
     
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  5. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
    2,668
    #5 vincenzo, Feb 10, 2020
    Last edited: Feb 10, 2020
    Drop a drain plug and chaos ensues. Catastrophe.

    Nobody wants that... there is a subconscious tendency to over tighten these plugs.

    There is a better way to ensure that they remain tight.

    NO NEED TO OVER TORQUE.

    PS: anti-seize on the male threads and anti-seize between the bolt and washer... but not between the washer and block.




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  6. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Are you sure about that oil tank thread size? I'm (almost) certain that the stock TR oil tank drain plug is an M16 thread. (Mine, too, had stripped out -- the design flaw is the length of thread engagement is just way too short for an aluminum female thread -- but rather than helicoil, I retapped it to M18 and used an M18 drain plug with a longer threaded portion.)
     
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  7. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
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    You are correct. It is. Sorry for the misinformation.

    Yes the plug is too short. I have seen some people put the oil pan plug in the tank because it has a longer reach and is the same diameter. The factory put helicoils in so many things including some of the drain plugs but not that one. The 288 GTO uses the pipe threaded oil temp sensor as a drain. Only a matter of time for that to be an issue no matter how careful you are.
     
  8. turbo-joe

    turbo-joe F1 Veteran
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    on my BB I can not open the drainplug anymore. tried it several times but no success. so I removed the temperature sensor to drain the oil
     
  9. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
    2,668
    Pull the four bolts that attach the drain plug housing. Get the housing on the bench with penetrating oil and heat. Let it then soak overnight. Next am... Hit it with an impact after a few more heat cycles.

    Something will give ;)

    PS: check for parts availability before getting crazy with it.
     
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  10. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
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    This might be worth considering. Check with manufacturer for part number and dimensions.

    I have two of them in service in machinery without oil filters (snow blower/ chipper).


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  11. Steve Magnusson

    Steve Magnusson F1 World Champ
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    It is baffling that they didn't use the same drain plug in both places just to not have so many different parts -- sounds like two Engineers never talked to each other ;). Plus the available depth in that tank bottom casting is huge so it's not like they couldn't have used a longer thread on the drain plug. Still, they should've put a heli-coil there as you noted.
     
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  12. c4b4the04

    c4b4the04 Karting

    Jun 9, 2017
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    Northern Virginia
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    Cassidy

    Aaaand it looks like I'll be returning the Helicoil kit.. so it's a M16, still the 1.5 or different thread?
     
  13. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Pretty sure the thread pitch is 1.5mm.
     
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  14. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
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  15. c4b4the04

    c4b4the04 Karting

    Jun 9, 2017
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    Northern Virginia
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    Cassidy
    Thank you, this is perfect. Just ordered the correct size Helicoil kit and will return the other. Glad my oil tank has this removable piece, seems like some don't?

    Thanks everyone, there's a steep learning curve on this gal. Currently wading through the posts regarding transmission oil (unrelated service item).... then will order that too.

    Cassidy
     
  16. turbo-joe

    turbo-joe F1 Veteran
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    why not use time sert? much better than helicoil
     
  17. c4b4the04

    c4b4the04 Karting

    Jun 9, 2017
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    Northern Virginia
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    Cassidy
    Honestly never heard of it. Thank you for the info. I have done some Toyota cylinder heads where the block strips and this is a much better solution. Thank you! I'll still go Heli on this, just as I have the bits all in place but I'll know for next time!
     
  18. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
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    The time sert is better BUT much more difficult to install straight and true. Since the part can be easily removed and taken to a proper machine shop it is definitely worth consideration. If you have a drill press and use great care you can do a time sert at home. I would not try it with just a hand drill.
     
  19. turbo-joe

    turbo-joe F1 Veteran
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    then you just can weld all and make a new thread original size. but I always prefer the time sert - did only good experiences. also easy to install. since I know time sert I never used helicoil - so more than 30 years now
     

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