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92 Temp Sensor on 98 HO engine?

NeXJ

NAXJA Forum User
Location
Los Angeles
I have a 92 XJ whose engine I swapped in 2000 for a 98 HO... but all this time I've been running without engine temperature readout. The whole problem is that the temp sensor for the 92 is physically and electrically incompatible with my 98 engine. It occurred to me I could try to find the 98's engineeering/casting drawings and figure out a good place to tap a new hole- though it seems risky and like a real pain in the hiney. At one point I had a mechanic fab up an adapter to run the 92 sensor at the coolant junction (where a bunch of hoses meet - up next to the windshield washer fluid reservoir) though inexplicably, that never seemed to function properly.

I was hoping that someone here might have a particularly brilliant idea about how to solve this - or (even better) personal experience with a similar issue...
 
Easiest thing to do is drill and tap the flat spot on the front of the thermostat housing for 1/8 NPT thread, install the sender there, and extend the gauge wire under the injector loom. That is what I ended up doing after swapping a 99 engine into my 91. You can also use the block drain plug below the exhaust manifold, but you'll need a 3/8 to 1/8 NPT adapter, and you'll still need to extend the wire (as well as be careful to avoid making contact with the exhaust). One other thing to consider is that the thermostat housing changes temperature very rapidly while the block changes temperature very slowly.
 
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You don't think re-boring and/or somehow adapting the existing hole would be a little more 'elegant' (i.e. simpler, shorter, less prone to problems)? Or did you find that solution unworkable for some reason...?
 
Temperatures vary throughout the engine--coolant at the head will tend to be hotter than coolant lower in the block, in the radiator, in a heater hose.

You can do as ehall recommended--probably the easiest. You can crawl under the engine, and remove the drain plug in the block and put a sensor in there, just be sure to route the wires so they won't get fried on the exhaust.

You can buy a dual-port thermostat housing from Hesco.

You can buy a sensor bung piece to splice into a radiator hose or heater hose from summitracing.com

You have options, you just need to decide what you want to do.
 
You don't think re-boring and/or somehow adapting the existing hole would be a little more 'elegant' (i.e. simpler, shorter, less prone to problems)? Or did you find that solution unworkable for some reason...?
I was tempted to do that, but I eventually decided that it was a lot of potential problems for no technical benefit. Use the drain plug if you want a clean installation. It'll work fine if you can find some of the O2 sensor sleeving that withstands high temperatures, maybe a junkyard donor or somewhere.
 
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