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Coolant temp sensor locations

I'm going to run a dry lower intake on my Merkur 2.3. Where would be another suitable location for the sensor?

WELCOME to TurboFord, Mike! I'm curious...... how are you planning to "dry" the lwr intake? RU just gonna use a propane intake gasket, OR, RU gonna weld a block-off plate into the manifold's coolant port?

No matter, there aren't a whollotta "ports" in the block or head of a Lima that can be used to get an accurate coolant-temp reading. There's a port at the rear of the block on the driver's side (right below the oil-pres sender in the head) that's used to report temp to the dash gauge ~ AND there's another port on the passenger side of the block, just below the rear core/freeze plug that was used to supply coolant to the water-cooled turbos. If THAT one is available, I suggest installing the gauge sender there and putting the computer's ECT in the port at the L/R of the block.

If both are already in use, you can use a hose-mounted "port", like those available from various suppliers (4-Seasons brand shown below). Install it in the heater hose that SUPPLIES coolant to the heater core, as opposed to the one that receives coolant AFTER passing thru the core. Also, don't "T" off a port to install two sensors (as you could with a pressure sensor), since the temp-sensing "bulb" must extend into the water flow for an accurate reading. <shrug>

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Placerville, California
(former)  '78 2.3T Courier w/blow-thru Autolite 2bbl carb ~ (current)  '87 2.3T Ranger w/PiMP’d EFI

Ray, do you know what size the threads are in the holes to coolant passage on the driver's side and passenger's side of the 2.3L SOHC engine block ? It looks like the 3/8 - 18 NPTF sensor might screw right into the driver's side hole.

YES, they're both 3/8 NPT, Dan. As a preemptive strike, however, if either of youse guys are planning to use the port on the passenger side of the block and it's plugged (not factory-equipped with a water-cooled turbo)...... that plug is often/usually rusted in there ADT (awfully damn tight). So, use plenty of penetrating oil (PB Blaster, Liquid Wrench, etc.), but you may ultimately have to drill it out and pick the remaining thread "coil(s)" out with an awl.  <eek>

Another consideration..... that pass-side "port" isn't a very good place to get an accurate reading of the engine temp. The main "water path" for cooling [other than a few "transfer" passageways in the deck] in a Lima is: (1) Cooled water drawn from the rad into the w/pump thru the lower hose, (2) Pumped/pressurized by the w/p into the front of the block, (3) Thru the length of the block to the rear, (4) up into the back of the head, (5) Thru the length of the head to the front, and (6) Thru the t/stat and upper hose, back into the rad for cooling.

Sooo...... as you can tell, the coolant flowing past that passenger-side port has only drawn heat from about 1/3 of its' total travel, AND ~ most of the engine's heat is created in the head, as opposed to the block. That's probably why Ford chose to sample coolant temp for the ECU after it passed about halfway thru the head on its' way back to the rad. 

Ergo, if you wanna give the computer the most accurate temp reading, you COULD gut the plenum-heating "chamber" from yer manifold and fab/weld an aluminum plate with a threaded hole for the ECT sensor over the coolant port (as below). OR...... at the very least, put the ECT in the rear block port in place of the existing gauge sender. If neither are options, I suggest using a "hose adapter" like the one I posted previously in the heater hose exiting the t/stat housing (where the coolant has already passed thru the entire circuit). My 2¢...... <shrug>

Finally (whew!), when looking at the coolant hose/pipe circuit in the last drawing..... keep in mind that BOTH hose nipples on the w/pump are (more or less) suction, whereas both on the t/stat housing are (m or l) pressure. Also, the small hose nipple on the t/stat housing is always "open" to the head jacketing and therefore always has flow, regardless of whether or not the t/stat has opened. <thumbup>

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Placerville, California
(former)  '78 2.3T Courier w/blow-thru Autolite 2bbl carb ~ (current)  '87 2.3T Ranger w/PiMP’d EFI

Ray, as usual, a lot of good information.

On my '88 XR4ti there are 3 coolant temperature sensors and they all monitor the coolant temperature in the lower intake manifold. There is the EEC-IV ECT sensor on top and then the instrument cluster gauge underneath and the cooling fan switch underneath. I have been running without coolant in the lower intake manifold for a few years now and I have not yet relocated any of the sensors.

My car is not a daily driver and I go out mostly on warm days. I have not noticed any driveability issues so far. On a cold day, below 60 degF, it does take a little longer for the fuel system to go into closed-loop fuel control. Not too big a problem. I do worry about missing the protection of the cooling fan switch and I did overheat once, when I forgot to turn on the cooling fan when I was stopped and idling for a long time on a hot day.

I bought the Heater Fitting Tee (Four Seasons 84540) to put a coolant temperature sensor in a 5/8" heater hose. I am disappointed that the sensor did not screw into the Tee very far and won't be down where the coolant flow is going to be. Maybe that is because the sensor thread is NPTF = National Pipe Thread Fuel.

If I can remove the factory plug on the driver's side, I am now thinking I will put the EEC-IV ECT sensor in the threaded hole on the driver's side of the block.

Hmmm........ I've never heard of the driver's side port being plugged from the factory, Dan. Nor have I heard of 3 temp sensors in the intake. In addition to the top-mounted ECT sensor, I HAVE seen the single-pin fan switch and knock sensor (blind hole) underneath. But the gauge sensor almost always occupies the rear block port on the driver's side. I guess the Merks had their way of doing things, lol.

The bulb should be close enough to the water flow to get an accurate reading with that 4-Seasons hose adapter. If you want it closer/deeper ~ you COULD cut off, say, 1/2" of the "hex" and use a 3/8 NPT tap to cut the tapered threads deeper into the adapter. Frankly, I doubt that doing so would make much (if any) difference in the reading.  <shrug>
Placerville, California
(former)  '78 2.3T Courier w/blow-thru Autolite 2bbl carb ~ (current)  '87 2.3T Ranger w/PiMP’d EFI

I suppose that even if an air bubble got trapped in the leg of the tee that has the sensor, it seems the air bubble would be at or near coolant temperature reasonably quickly.

On the XR4Ti: The gauge sensor is one wire, but the fan switch has two wires.

On my past combo's, I have kept the manifold "wet" by running a -6 AN line from the DS rear of block to the lower intake. This let me keep my ECT in the intake between 2 & 3. I also feel like it was worthwhile to bring some water from the rear of the block to the middle of the head since it didn't already pass across the rear 2 holes at the head. No proof it did anything other than let me keep the sensor in the shock location.

On my tall deck with SVO head, I have no water in the intake and no provisions anywhere for it. I am running the ECT in the driver side rear of the block since it's already 3/8" NPT.
84 Capri RS Turbo
1/8th 6.29@110, 1/4 - 9.87@137

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