Relocating temp sensor/help figuring out threads:

Ok so I am using a 01 XJ engine in a 96 XJ, got it running last night but I have this one last problem to solve.

The 97+ engine uses the ECU temp sensor and broadcasts that signal on the CDD bus where the gauge cluster picks that up, the 96 system uses a sensor for the ECU and a separate sensor for the temp gauge in the cluster.

The simplest solution I can see is to relocate the stock temp sensor up by the ECU temp sensor in the thermostat housing. To that end:

Can anyone who has done this same swap tell me either their solution, or what the correct tap size is?


Second, lets assume no one else has ever done this(or at least done this and posted results so that I could find them in the search). I need to figure out this tap size.

The major diameter of the sensor reads .391 in, or 9.93 mm. My thread gauge here shows the threads to be 27TPI.

As far as I can tell 27TPI is not any regular thread, which makes me think this thread is metric.

So it looks like 9.93mm means M10, 27TPI = 0.941 mm pitch(I don't have a metric thread gauge), so it might be M10x1?

Any other thoughts for me?

The head should still have a flat spot near the fire wall that can be drilled and tapped for the temp gauge sender.

The threads are probably pipe tap threads.

There is a flat spot on the front of the tstat housing that works well. You can extend the sensor wire and run it under the loom along with the others.

The thread size is 1/8 NPT (tapered plumbing thread), almost any hardware store should have one, they are cheap at Lowes et al

I put a 98 motor in my 96 and came across this problem.I mounted a coolant flush kit in the top hose running along the valve cover and mounted it in the cap that came with the kit.I put a jam nut on the back side of sender and it's worked great for almost 2 years now.Take the sender to Home Depot so you can get the right nut.I had to get one from the lighting department.It's a lamp thread.The kit was like $7 and the nut was $1.Good luck with it.Almost forgot,I grounded the sender to the firewall.Just wrap one end of the wire around the sender and bolt the other end to the wall.

Tim_MN said:

The head should still have a flat spot near the fire wall that can be drilled and tapped for the temp gauge sender.

The threads are probably pipe tap threads.

Click to expand...

It does, the only reason I didn't go that route is that I was unsure if the internal passages had changed at all and I would rather not mess up a head.

ehall said:

There is a flat spot on the front of the tstat housing that works well. You can extend the sensor wire and run it under the loom along with the others.

The thread size is 1/8 NPT (tapered plumbing thread), almost any hardware store should have one, they are cheap at Lowes et al

Click to expand...

Yes, that flat spot is exactly what I was planning, and yes extending the wire and running it along in the injector loom/plastic cage.

ok so 1/8" NPT.......excellent thanks, I was pretty convinced it was M10x1, glad I didn't buy that tap.

troys 96 xj said:

I put a 98 motor in my 96 and came across this problem.I mounted a coolant flush kit in the top hose running along the valve cover and mounted it in the cap that came with the kit.

Click to expand...

That was the other thing I was thinking, a flush or cap kit and tapping it there, but I think drilling and tapping the housing should work nicely too.



Thanks all! Out to search through my tap sets for a 1/8" NPT tap.

On mine ,the fan is too close for comfort so I did it this way.

Ehall's is the quickest and cheapest solution.

You can order a two-sensor thermostat housing from Hesco, or get a heater/radiator hose threaded bung "splice", Hesco or summitracing.com are a couple of sources for those.

IF you go with ehall's suggestion, you need to go VERY SLOW with the tap in the thermostat housing--go too deep and the sensor won't seal--the NPT tap can cut to a taper greater than the body of the sensor.

Gauge temp sensor relocated:



So one challenge down, now I got a misfire and a CEL to track down. But, WOOT, progress!

if you are up to it, the pre-92 (ish) gauge sender had an angled connector that does not stick out as far



I went to a junkyard after the first setup and pulled about 4 feet of the sender wire from a harness, makes it low profile and the wiring is much cleaner

ya, If I had known about that earlyer I would have pulled one. I'm done and the wiring is soldered in place. Moving onto the next problem....CPS issues.