Jamrock37

Hey guys,
I recently noticed that my temp gauge isn't working. I know the problem is that the temp sensing unit has become disconnected. I've done all the research I can on this and I know that I'm looking for the connection point at the back of the block. Problem is, I've looked EVERYWHERE for this point and I cant find it anywhere. I have a 1990 XJ, and I could really use some help figuring out where the hell this sensor plugs in. Is there potentially a different connection point that I'm unaware of???

PatHenry

It's possible that someone used a head off a 97+ engine and relocated the sending unit (probably to the t-stat housing).

Jamrock37

Thanks I'll look into that possibility.

bluejeep2001

the temp sender is a small 1 pin plug near the back of the head 2 or 3 inches fwd of the back on the top right where the valve cover meets the head. on the drivers side of the head . even if someone installed a late model head with only the sender in the tstat...your ecu would not be programed to look there for the information. the connector should still be there somewhere. the sender is the same size and shape as your intake manifold temp sender I have an older head in the garage I will take a picture of it to show you the sender

Jamrock37

Thanks I would appreciate a picture because I was pulling my hair out trying to find this and I couldn't. I downloaded the shop manual and saw the picture of what it is suppose to look like, and it's just not there. I'm stumped!

djgrayxj

Note from DJ on Head casting number by years
The 87 to 95 heads have the port for the coolant temp gauge sending unit.
Head casting number by years; Casting numbers are as follows:
Year............Casting No
1987-90......2686
1991-95......7120
1996-99......0630
2000-01......0331
It is easy to determine what head you have. On the driver’s side, about halfway down the cylinder head between #3 & #4 fuel injector but below the valve cover clean the lip of the head with a rag or solvent if really greasy. With a good light, you can read the casting number of the head.
Example:

Jamrock37

And if I dont have the head with the port, what am I looking for then? I know I've got the L shaped single wire female end... so wouldn't that tell me that I'm looking for the pin bolt?

Jamrock37

This isnt my photo, but everything i look up tells me this is what im looking for, and this simply is non existant under my hood, which is why i am at a complete loss...

dave1123

If it's a later model head, it may not have the rear sensor, in which case it will only have one in the thermostat housing. The problem with that is that sensor is different and may not work with your gauge. What you'll have to do is install a pipe reducing bushing in the thermostat to accept your type on sensor and extend the wire to reach it.

Jamrock37

I'll check that out because my temp gauge definitely use to work so the sender must have been attached to something. Thanks

cruiser54

See post 8. Clear as a bell.

Jamrock37

That's my post

cruiser54

And a great one it is!!

Jamrock37

Turns out the head is from 2000-2001 (0331)
so any ideas on how to fix my temp gauge now?

cruiser54

Got any pics of this install and manifolds?

You can always extend the temp gauge wire and locate the sender in the thermostat housing.