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K Sump Plug Thread

Dan J

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Can anyone tell me the thread on a K Wet sump plug?


It looks v similar to the M14 x 1.5 on an Oil temp sender i have sitting here on my desk....


Sods law says they're different, the question is by how much?


Dan J

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My 1.4K SS sump plug was (and still is, I guess 😬)

1/4"BSP (British Standard Pipe)

55Deg Thread - 19 TPi

O/D .518" (13.15mm)

Pitch .0526" (1.33mm)

Tapping size 11.8mm (0.4646")


I bought the correct Helicoil kit which came with about ten inserts, the correct size drill bit which won't fit into a 13mm chuck *mad* (thus I bought a bigger chuck as well).


I guess you're intending to fit an oil temp sender like Chris, but if it's a thread repair you need, you're welcome to borrow the stuff.





*eek* That's your company car !?! *eek*

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I'm sure Dave is correct. When I said "M13", I measured the o/d as 13mm and, to be honest, it never occured to me that it might not be metric. So go with his determination of the plug size as he seems to know exactly what it is.


BTW, if you are intending to drill it to take an oil temp sender, I checked offline with Roger King (of Roger King Engines fame)as to whether this was sensible or not because I received a whole range of answers to my query at the time on Blatchat which ranged from thumbs up to thumbs down and lots of inbetween responses. That's why I wanted the advice of an acknowledged engineering expert.


The issue is that my sender is a 1/8th NTPF fitting and after drilling would only leave about a 1mm wall of plug around the sender. The diameter of the sump plug to the base of the thread being approx 11mm, and the tap drill being 8.7mm (11/32nds). I wasn't sure whether this was enough "meat" or not.


Roger was extremely helpful. Although he cautioned that he hadn't done this himself, he advised that the thickness left (ie: 1mm) should be sufficient if drilled carefully. I ordered another sump plug from CC first, just to be on the safe side (It was only a couple of quid including a new copper washer) and fitted the oil temp sender in the sump plug with some PTFE tape to help the sealing.


I have been running with this arrangement for about 6 weeks now and it works superbly. Not the slightest hint of an oil leak from it. I was amazed though how long it takes for the oil to get up to temperature. Whereas the water is hot within say 3 or 4 minutes running, the oil takes maybe 10 minutes or longer to register on the gauge (which starts at 50degC). Once hot, the oil runs at about 70-80 degC normally, rising to 90degC when driven hard but drops quickly back down to 80degC if you ease off for a couple of minutes. Even when driven really hard for a prolonged period, it doesn't rise to more than 90-95degC. All this is road use BTW.


Roger King did caution also that if the sump plug is one with a magnet attached (which mine isn't) he would not advocate drilling the plug and thereby removing the magnet. He suggested in this case that one could drill the sump itself (obviously having removed it first).




1.8K SV 140hp see it here


Edited by - Chris W on 11 May 2003 11:12:26

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Thanks chaps for the replies.


The temp sender in question is way too big to be let into the sump plug so i wondered whether i could recut it to the correct thread to 'be' the sump plug.


On examination this looks a tad risky so i'm having a brass adapter made up to give a female M14 x 1.5 to Male 1/8npt so i can fit the sender straight into the side of the Apollo where it's meant to go.


Dan J

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