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Repairing The Sump Plug Thread


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#1 Shooter63

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Posted 26 July 2020 - 05:28 PM

A few of you might know that I bought a mk1 mini from Europe last year, I finally got round to doing an oil change, when taking the sump plug out half the threads in the case came with it( not good ) as the engine is being replaced with a different unit some time next year I was going to bodge it with a MS taper bung, but then thought " naaa do it right" so this is how I did it
Buy helicoil kit
Buy 21/32 drill bit ( more on this later)
Jack car up and onto axle stands
Take off O/S wheel
Crack off the lower ball joint ( this will allow the tie rod bolt to be removed)
Remove tie rod
You will now have a clear line of site to the sump plug, now you have to drill the clearance hole for the tap that comes in the helicoil kit, I went straight in with the 21/32 drill bit but boy does it grab, I would recommend using a 14mm then 15mm then going with the 21/32 bit. Another problem is trying to find these size of drill bits with a reduced shank to fit in a cordless drill, I'm lucky as I have a lathe so I turned the shank to 12mm but if you haven't got this type of gear, the drill bits can get really expensive. I also turned up a couple of guides for the drill and tap to keep them nice and square. The tapping of the case is just like any other tapping operation except I removed the tap totally to keep cleaning the swarf off ( both drill and tap were greased to catch the swarf). Run the tap right in to make sure you have a full thread, next it's time to fit the helicoil, the ones that came with the kit are 1.5D this means 1.5 x the diameter of the thread which is a bit long for my liking so I cut 1 coil off with a dremel type tool, the actual fitting of the helicoil is the easy bit, just wind it in using the the tool provided making sure the coil sits below the face where the sump plug fits, then just snap the tang off and jobs a good un, just me but I did put a couple of drops of thread lock on the helicoil for good measure, your sump plug will now fly in and out like never before. I did replace the copper washer with a Dowty type and a bit of gorilla snot on the plug thread though probably not needed. Then just a case of putting the tie rod back on, doing the bottom ball up and wheel back on. Total time including many fags an hour or so

Shooter

#2 Moke Spider

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Posted 26 July 2020 - 08:24 PM

Cheers for that write up of your experience. Yes, in some situations, I too put some Red Loctite (I can't recall the grade) on the Helicoils if I don't want them to move. The Red Loctite is a permanent one.

 

I made a guide too for drilling the hole square. If's a piece of flat bar, bent in to a Z shape. It bolts on to 2 nuts on the Transfer Case / Gearbox and has a neat (on the drill) hole in it that stands about 2" off the Gearbox Face, then it's pretty much a no brainer. I use the same guide on the Tap too, by chance, the shank of the Tap it the same Dia of the Drill.

 

Yes, having a steel insert for the Plug to screw in to is like night and day compared to screwing them in to a Thread in the Aluminum. I don't do the Helicoil repair for these plugs but I make up a poor man's Timesert from an M20 Bolt (there's been a few threads on the forum  with these) and given that so many of the Plug Threads are so poor now or will be in time, I now just fit these Inserts as a matter of course when Overhauling any Gearbox, only, at that time, I do them in the Mill, so I don't need that guide.



#3 floormanager

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Posted 26 July 2020 - 08:31 PM

Love to see a photo of the guide.  Changed my oil yesterday.  No problems with the thread.  I also use a dowty washer.

Paul



#4 Shooter63

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Posted 26 July 2020 - 10:26 PM

Cheers for that write up of your experience. Yes, in some situations, I too put some Red Loctite (I can't recall the grade) on the Helicoils if I don't want them to move. The Red Loctite is a permanent one.
 
I made a guide too for drilling the hole square. If's a piece of flat bar, bent in to a Z shape. It bolts on to 2 nuts on the Transfer Case / Gearbox and has a neat (on the drill) hole in it that stands about 2" off the Gearbox Face, then it's pretty much a no brainer. I use the same guide on the Tap too, by chance, the shank of the Tap it the same Dia of the Drill.
 
Yes, having a steel insert for the Plug to screw in to is like night and day compared to screwing them in to a Thread in the Aluminum. I don't do the Helicoil repair for these plugs but I make up a poor man's Timesert from an M20 Bolt (there's been a few threads on the forum  with these) and given that so many of the Plug Threads are so poor now or will be in time, I now just fit these Inserts as a matter of course when Overhauling any Gearbox, only, at that time, I do them in the Mill, so I don't need that guide.


The next box I do will be a m20, but i think I'll tap it m14, then you can pick up a sump plug anywhere

Shooter

#5 tattooguy08

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Posted 02 August 2020 - 09:50 PM

A few of you might know that I bought a mk1 mini from Europe last year, I finally got round to doing an oil change, when taking the sump plug out half the threads in the case came with it( not good ) as the engine is being replaced with a different unit some time next year I was going to bodge it with a MS taper bung, but then thought " naaa do it right" so this is how I did it
Buy helicoil kit
Buy 21/32 drill bit ( more on this later)
Jack car up and onto axle stands
Take off O/S wheel
Crack off the lower ball joint ( this will allow the tie rod bolt to be removed)
Remove tie rod
You will now have a clear line of site to the sump plug, now you have to drill the clearance hole for the tap that comes in the helicoil kit, I went straight in with the 21/32 drill bit but boy does it grab, I would recommend using a 14mm then 15mm then going with the 21/32 bit. Another problem is trying to find these size of drill bits with a reduced shank to fit in a cordless drill, I'm lucky as I have a lathe so I turned the shank to 12mm but if you haven't got this type of gear, the drill bits can get really expensive. I also turned up a couple of guides for the drill and tap to keep them nice and square. The tapping of the case is just like any other tapping operation except I removed the tap totally to keep cleaning the swarf off ( both drill and tap were greased to catch the swarf). Run the tap right in to make sure you have a full thread, next it's time to fit the helicoil, the ones that came with the kit are 1.5D this means 1.5 x the diameter of the thread which is a bit long for my liking so I cut 1 coil off with a dremel type tool, the actual fitting of the helicoil is the easy bit, just wind it in using the the tool provided making sure the coil sits below the face where the sump plug fits, then just snap the tang off and jobs a good un, just me but I did put a couple of drops of thread lock on the helicoil for good measure, your sump plug will now fly in and out like never before. I did replace the copper washer with a Dowty type and a bit of gorilla snot on the plug thread though probably not needed. Then just a case of putting the tie rod back on, doing the bottom ball up and wheel back on. Total time including many fags an hour or so

Shooter

What size was the tap? (helicool kit)



#6 Shooter63

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Posted 03 August 2020 - 07:27 PM

A few of you might know that I bought a mk1 mini from Europe last year, I finally got round to doing an oil change, when taking the sump plug out half the threads in the case came with it( not good ) as the engine is being replaced with a different unit some time next year I was going to bodge it with a MS taper bung, but then thought " naaa do it right" so this is how I did it
Buy helicoil kit
Buy 21/32 drill bit ( more on this later)
Jack car up and onto axle stands
Take off O/S wheel
Crack off the lower ball joint ( this will allow the tie rod bolt to be removed)
Remove tie rod
You will now have a clear line of site to the sump plug, now you have to drill the clearance hole for the tap that comes in the helicoil kit, I went straight in with the 21/32 drill bit but boy does it grab, I would recommend using a 14mm then 15mm then going with the 21/32 bit. Another problem is trying to find these size of drill bits with a reduced shank to fit in a cordless drill, I'm lucky as I have a lathe so I turned the shank to 12mm but if you haven't got this type of gear, the drill bits can get really expensive. I also turned up a couple of guides for the drill and tap to keep them nice and square. The tapping of the case is just like any other tapping operation except I removed the tap totally to keep cleaning the swarf off ( both drill and tap were greased to catch the swarf). Run the tap right in to make sure you have a full thread, next it's time to fit the helicoil, the ones that came with the kit are 1.5D this means 1.5 x the diameter of the thread which is a bit long for my liking so I cut 1 coil off with a dremel type tool, the actual fitting of the helicoil is the easy bit, just wind it in using the the tool provided making sure the coil sits below the face where the sump plug fits, then just snap the tang off and jobs a good un, just me but I did put a couple of drops of thread lock on the helicoil for good measure, your sump plug will now fly in and out like never before. I did replace the copper washer with a Dowty type and a bit of gorilla snot on the plug thread though probably not needed. Then just a case of putting the tie rod back on, doing the bottom ball up and wheel back on. Total time including many fags an hour or so

Shooter

What size was the tap? (helicool kit)

I think they are special taps made for the job, the tap comes with the kit, but in these sizes no drill bit is supplied

Shooter




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