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[Dave69]

nice and simple for someone

taper thread size on the temperature sensor for the block on the cj7?

previous owner put a parallel which is now defunct

[Nosebolt]

mine have all been parallel 

[eastryjeep]

The 6/258 and 232 lumps are both tapped 1/8" BSP x 28 tpi.
But dont do the plug or sender up too tight as it can easily burst that little boss and then you are well stuffed!

Got that tee shirt when I was younger and even more stupid!

[Dave69]

some images on line i have seen indicate a taper thread, the sensor already in place does not tighten son hence the thought it might have been a taper with a parallel thread sensor used.

1/8th BSP it is then.

[Delk]

I would be surprised if it was 1/8 BSP since the Jeeps are not British. I would guess it would be 1/8 NPT since Americans have to different.

[Dutch]

If you get it working let me know.

I got one from Lighty's (crown) and they gave me a 50% chance - in their words "it's only good for plugging the hole.

Then with my new clutch order from Morris 4x4 I ordered one from the states (thinking it was an original one) but was also flippin' crown and didn't work either.

Original ones (is that OEM  .... what does that actually mean?) are 40 quid or something stupid.

[eastryjeep]

1/8" BSP is 28 tpi & 1/8" NPT is 27 tpi, not that you would notice till too late at that size, but the NPT is about 0.010" bigger on the major dia I think.
As I said before, I bust my block by overtightening my oil sender so that was definitely BSP!
Also every sender unit I've ever fitted to my 258 has been tapered too, but if you want to fill a redundant hole you could put PTFE tape on the thread for a bit of bite and a crush or copper washer under a short banjo bolt.
Try BSP first, but if it's still loose then go up to the NPT.

Another option would be to carefully re-tap M10 with a vacuum cleaner collecting the swarf as you go, then fit a bolt with a copper washer under the head and Loctite on the thread, or maybe just Loctite a grub screw in there, just don't block the oil passage with swarf or the bolt will you!

[Dave69]

was thinking about re-tapping to 10mm, sensor goes into the water jacket. thread tape is another option but not the solution plus it stops the earth path for the electric connection

[eastryjeep]

Sorry, when you mentioned the block in your first post I assumed you had meant the oil pressure sensor. I also thought you said the hole was redundant, and as there are so many other plugged holes in that area I guessed you were taking pressure readings from one of them!
Anyway, if the offending hole is'nt needed any longer, electrical continuity hardly matters so I'd still put PTFE tape as you'd be hard pressed to isolate the sender body from the earth return whilst maintaining a good mechanical seal and if you did manage it I'd expect the thing to pop out like a cork when you got some pressure in the system!
The original temp sensor on my cylinder head is right at the back, near cyl. No. 6, it too is a fine thread but doesnt go into the water jacket, it just heats up with the cast head. I don't remember it being a taper thread either, but will check if needed.
Cheers, Nick.

As an after thought, why not re-tap, fit the M10 bolt n copper washer to fill the hole, then fit an XJ thermostat housing and sender so you can see true coolant temp?

[Dave The Sparky]

The coolant temperature sensor should be sat in coolant at the back of the head(near cyl6)
Reason i know??
When i refilled my coolant after rebuilding the engine it wasn't there and the antifreeze mixture went all over the floor.

[Dave69]

thinking of blanking the thread and inserting a sensor in the top rad hose and reading that.

[eastryjeep]

4L XJ thermostat housing swap is too easy to disregard Dave, the mounting bolts are just a different length!

[Dave69]

i'll have a look into that