Temp sending unit broke

[kmerian]

Went to vent my block the other day, put my 13mm deep socket on the temp sending unit and it snapped right off level with the block, with the threaded portion of the unit still in the block. HELP!!!!

[Jeepme]

Easy out.

[Saudade]

Well that's not good.

As Jeepme says, you can try using an easyout to remove the stub. Put some heavy grease on the drill bit to catch any chips. If you break the easyout, you're pretty much screwed.

If it's not leaking antifreeze, you might consider leaving it alone. You could use a newer model (92 and later I think), thermostat cover which has the boss for the sending unit in it and patch in a longer wire.

[kmerian]

It's not leaking antifreeze, how exactly would I set up the rig you suggest? I notice that in the sending unit half still in the block, there is a thin metal strip in it, is that what I would solder the new line to?

[MagicRat]

Originally Posted by kmerian

It's not leaking antifreeze, how exactly would I set up the rig you suggest? I notice that in the sending unit half still in the block, there is a thin metal strip in it, is that what I would solder the new line to?

No.
Saudade means to just leave the broken piece as-is just to plug the hole. It's likely not functioning, so do not solder anything to it.
He suggests, and I agree with him, to get a NEW sending unit and find a place to put it.
As he suggests, the '92 and later thermostat housings have an extra hole you can screw a sender to and just lengthen the electrical wire to reach it.
If you are lucky, you might find another threaded hole (that goes into the water jacket) that just has a metal plug in it right now. You may be able to remove the plug and screw in a sender.

I am not sure about Jeeps, but as an example, small block Chevys often had 4 sending unit holes (2 per head) but only one was used for a sender. The others were plugs, so in theory you had 3 extra holes for thermostat senders.

Just look around and you might find something.

[Saudade]

Thanks Magicrat for clarifying.

I checked a 94 parts manual and it show a plug where the hole in the head is for the older sending unit. I didn't notice any others so it may be the only hole.

I suggested using the other thermo cover since the guys that swap out the closed cooling system for an open one need to relocate the elec fan thermo switch. It seems like a reasonable place.

[Stick89]

Originally Posted by Saudade

Thanks Magicrat for clarifying.

I checked a 94 parts manual and it show a plug where the hole in the head is for the older sending unit. I didn't notice any others so it may be the only hole.

I suggested using the other thermo cover since the guys that swap out the closed cooling system for an open one need to relocate the elec fan thermo switch. It seems like a reasonable place.

Either that or wire the fan to a swtich,that way you turn it on when you want to

[MagicRat]

Originally Posted by Stick89

Either that or wire the fan to a swtich,that way you turn it on when you want to

Good point.
I assumed the broken sender was for the gauge on the dash. If its the fan switch, this could work too.

[Saudade]

Before this gets too far off course, the sending unit on the back of the cyl head is for the dash gauge. The elect fan unit is located in the radiator of closed cooling system XJ's.

My suggestion was to not mess with the broken sending unit if it not leaking to avoid the possibility of doing more damage to the head.

That means relocating the temp gauge sending unit. The thermo cover seemed like the easiest place.