where to stuff the pick up sensor for the water temp on a '74- 232???

This is all on a '74 CJ5 6 banger 232 all stock, stock radiator, stock intake, exhaust, just old(er).
I've been pondering this move for a long time.
My water temp gauge just will not work.
I've replace EVERYTHING in the speedo housing to get the gas gauge and temp to work, tested the wire to the sensor, replaced the sensor, tested the sensor before installing it with a ohm meter and a pot of hot water.
If I groung the wire the gauge go up, but all hooked upi it bearly moves.

So, after replacing the heater core, (of course it started to leak when it got cold), the thermo, (a 180 first now a 195)I figured whilist the coolant dumped, I install a mechanical gauge.
The only place I could fit the sensor it was on the side of the block, removed a temp vacum switch.
So the gauge reads 150 the highest with a 180 thermo, 160 with a 195 thermo?
WTF! Oh well, I had this gauge on the shelf, it's been battered @ , I have no idea how old it is, must been off.
I spend the $20 for a Sun Pro gauge, do a quick switch, and WTF! same thing.
I get out my laser temp gun and shoot it at the block.
Yep, it's 160 down there, 130 at the thermo???????
(this was after I drove to work, (it was in the 20's out) ran it into the garage, let it idle for 15 minutes).
WTF?????? Ok pull the thermo, a pot of hot water and a thermo shows it opening and closing perfect.
So first question.......................................................................
1) why is my block 160 at the highest with a 195 thermo??? It should actually be HIGHER there close to the cylinder deep in the bowels of the engine??

2) where do other 232 owners put a mecahnical gauge??? I can go screwing in adpters in at the front of the motor, besides it being close to the water pump belt, you can get the sensor away from the block and screw up the reading.
Joe
So many question, so many ideas, for a old guy to handle! I shouloda taken up golf!roll:

 

Something I discovered when changing the ELECTRICAL sender in my 258 was that when the sender was placed in the hole below the manifolds, to the rear half of the block, I was getting a lower reading as well. I assumed it was because the colder water from the radiator was coming in and passing along the bottom of the block and hitting the sensor before the water had much chance to pick up engine heat. When I installed the same setup in the correct hole in the front of the head, everything read as it should.
I understand that it might be tight for your setup in the head front, but just wanted to tell you what I found on my install.

 

hmmm, so it's all working correct??? Cool beans!
Ya think it'd be hotter down there, but then sometimes I think too much!
Now that I think like a mechanical engineer- the flame and most of the heat is going to be @ the head area, down the bottom where I'm taking the reading, the oil is located there, and it's mostly air and the bottom of the piston in the cylinder hole.
So, that all being said, the temp BETTER be lower!
The high temp will be @ the squish and flame area.
I can see the temp on the gauge go up n down as the thermo opens and closes.
Most engines have like 3-4 places to stuff a sensor, but noooooooo, jeep has to be tough!
Joe
Yet another problem solved by sober minds!

 

The cooler water from the radiator picks up heat as it travels.
It is at its hottest at the front of the head where it activates the thermostat and temp sensor that should be in that 1/8NPT hole just under the thermostat housing.
Keep in mind that any electrical temp sensor is specific for the guage it is manufactured for. A new guage will not read correctly off the old factory sender or vice versa. Also, if you put too much sealant or teflon tape on the sensor, it won't ground through to the block.

 

I would not judge the temperature of the coolant from the temperature of outside surface of the block. If you want an independent confirmation that the coolant is near the set point of the thermostat, put a candy thermometer or similar in the open neck of the radiator. You can also measure the exact temperature that your thermostat opens by inserting the same thermometer in a warm pan of water with your thermostat. Then heat the pan and see at what temperature the 'stat actually opens. Dunking the stat in a boiling or near-boiling pot of water is a rather crude go/no-go test.

The sender is a thermistor - an electronic component that changes resistance with temperature. You can measure the resistance of the sender, or better, you can substitute a fixed resistance for the sender and see what the gauge reads. The TSM describes this process, though they call for a fancy special tool. Instead of the tool, get an assortment package of resistors at le Radieux Shaque and put them together in series or in parallel to get the resistances you need.

<edit> As DREDnot mentions, the sender is specific to the gauge. The sender is the most common failure. RockAuto shows a TS37 Standard or a 1T1161 Airtex-Wells for this application - no shortage of replacement parts. For the $6-8 retail price for this part, I'd just replace it.

 

tanks!
Decades ago, (Jesus I hate saying that!!) when I was going to trade school to be a "Mechanic" (we weren't "Service Techs" back then, just plain "grease monkeys"!), I had a instructor who beat into us- "Test Not Guess"!
I thought that was a cool saying and he made it up til I saw that saying on a old Sun scope!
40 years of spinning wrenches later and now I harp that at my boys.....
I've tested this simple cooling system, more than NASA test their rockets, (OK maybe more, look what happened to a few of those)!
That is basically what I did, (I didn't do the resister thing, it's not THAT critical, but I do have a bunch from testing motorcycle ignition systems), from point to point more than 1 time, (my lunch time is tinkering with the jeep).
I will try the electric senso without telfon tape and see if that changes the reading, but at this point I've given up on the OEM gauge.
After taking a ton of readings, I've conclude that I'll just have to do simple math!
Add 30 degrees to the block reading gets me just about the temp coming out the thermo.
It's the German mechanic in me that wants to make it correct.
Joe
It's the simple things that **** me off the most! But hey! It's a jeep, it's not supposed to ALL work! Right??

 

When I had my 5 with a 258, I ran an eletrical sendor in the block below the exhaust manifold wired to a dash guage. I had an additional sender installed in a 4.0L T-stat housing for my fuel injection system.

I compared the block reading to the reading in the fuel injection system. The block would take anywhere from 15 to 45 minutes of driving to reach the same temp the Fuel injection system was reading depending on the ambiant air temperature.