Adding a second Coolant Temp Sensor to a 97?

[hubs97xj]

I'm replacing my radiator soon, looking to do away with the radiator probe (for my fan controller). Flexalite sells an adapter, which should have the right bungs for FAL sensor, but aside from cutting up a hose, and clamping one of these in, what have folks done to relocate or add coolant temp sensors? They only sell two adapters, and I'm honestly not sure my upper hose is the right diameter in the right place to fit either one- the inlet/outlet diameters of the hose don't match either, and the hose itself seems to vary where it snakes around the compressor.

One major consideration is that the sensor needs to be within about 3 feet of the controller, which is currently on the passenger side of the firewall. That leaves the radiator (not wanting to shove a probe in a brand new radiator), cutting the hose, or getting a little more creative. Is drilling and tapping the Tstat housing a workable idea? Has anyone cobbled together an adapter that fits the upper hose well? Is there another suitable location for a CTS (the earlier models had at least two CTS, did they not?).

Kind of a stupid question to some of you, but it's been a bad month, and another couple hundred dollars worth of repairs is not helping my general focus. Appreciate any insight into making this work without throwing away $150 worth of aftermarket hardware.

 

[pb_beaker]

space the hood up and put hood vents on, dont worry about another sensor, stay thirsty my friend

 

[hubs97xj]

WTF, go run your post count up elsewhere.

 

[MoFo]

What year is your XJ? Engine the same year?

I'm replacing my radiator soon, looking to do away with the radiator probe (for my fan controller). Flexalite sells an adapter, which should have the right bungs for FAL sensor, but aside from cutting up a hose, and clamping one of these in, what have folks done to relocate or add coolant temp sensors? They only sell two adapters, and I'm honestly not sure my upper hose is the right diameter in the right place to fit either one- the inlet/outlet diameters of the hose don't match either, and the hose itself seems to vary where it snakes around the compressor.

One major consideration is that the sensor needs to be within about 3 feet of the controller, which is currently on the passenger side of the firewall. That leaves the radiator (not wanting to shove a probe in a brand new radiator), cutting the hose, or getting a little more creative. Is drilling and tapping the Tstat housing a workable idea? Has anyone cobbled together an adapter that fits the upper hose well? Is there another suitable location for a CTS (the earlier models had at least two CTS, did they not?).

Kind of a stupid question to some of you, but it's been a bad month, and another couple hundred dollars worth of repairs is not helping my general focus. Appreciate any insight into making this work without throwing away $150 worth of aftermarket hardware.

 

[hubs97xj]

It's a 97 with the 4.0.

 

[sjkimmel99]

I did the in-line hose adapter thing twice in my 96, once for a fan controller and once for a mechanical temp gauge adapter. Since the pic was taken I've removed the in-line water filler neck; multiple radiator caps failed to seal correctly and draw water back in from the overflow bottle. And yea, that's a piece of wood holding the hose up, works fine.

Sorry for the pic size but it's easier to see what's going on:

I used the 1 3/16" diameter one from here.

http://www.jazzproparts.com/AC_Autotechnic_Accessories_s/1335.htm

I had to drill out & tap the one for the mechanical gauge probe.

I am using 2 separate relays for power to the 2 fans and letting the fan controller run those so not much power goes through the controller. Using a Hayden controller now but started with a Procool one and Procool fan. The Procool controller started to stutter a lot before it would turn the fan on and the fan never pulled as much air as was advertised. The Hayden (from partsamerica) comes with a 1/8 mpt probe and fits in the in-line adapter. I'm using a ford product fan(bought from someone so don't know for sure what it came off of) which will stick small animals to the grill and the stock electric one.

FWIW at this point if I was to get another jeep I would stick with the mechanical fan until forced to since it's been such a PITA instead of just jumping into it without any real evidence of the merits of all-electric.

 

[hubs97xj]

That is excellent, thank you. I've hit a wall a couple of times now, not knowing where to look for some of the odd pieces, but that should be just about perfect, once I get a sender (still not entirely sure what I can use in that regard, as Flexalite hasn't responded to my email yet).

At this point, I'm still pretty happy with the electric setup. Hindsight being what it is, I'd have done a few things differently, but I think it's better than what I had before, and a good radiator, along with a better probe and fan mounting setup, should wrap the cooling system up nicely.

Is that the mechanical sender in the blue adapter, and the electric in the red? Your junk is clean under the hood- aside from the block of wood, I'm jealous.

 

[Wayne Sihler]

There is always a"T" adapter that you could put into the thermostat housing.Depending on the probe size of the aftermarket controler.The one I used was a GM one wire temp sender.

Wayne

 

[sjkimmel99]

Is that the mechanical sender in the blue adapter, and the electric in the red?

Yes, the blue one is the gauge sender. Just random choice as to the colors.

 

[hubs97xj]

I wasn't sure about a T in the Tstat housing, as that would bring the sensor out of the coolant, it seems, and also looked like a surefire way to get some air trapped there. I'd thought about drilling and tapping the housing for the second sensor, but it doesn't look like the casting is well suited to that -too thin where it would be convenient, and would likely put the sensor where a broken belt would kill it, and/or the sensor body might interfere with the T stat.

That adapter is looking good at this point, as I wouldn't have to modify anything but a hose, and I can keep my wiring clear of the belt.

 

[Dobbs]

Hello all I was thinking has any one every tryed the block drain plug below the manfold. looks like that would work. In fact there are two of them one in the front and back of the block on the manfold side.

 

[ehall]

I used the rear one for my gauge sender when I swapped a '99 into my '91. The temperature gauge is always about 15-20 degrees higher than the computer, probably because two cylinder walls are right next to it. I was talking to the mechanic that does my Cadillac electrical work and he said he'd put a potentiometer on it and figure out the correct resistance, then find a sensor that would compensate. I may try another sender first though--it could just be a bat unit.

 

[RichP]

I've never looked but does the rear valve cover bolt go all the way through the head into the water jacket the way the older models did ? Just a thought.
As for a T fitting, I don't think it would be accurate, as stated it would measure air temp not coolant temp Not like you can do with the oil pressure sender at all. You might also be able to put on in one of the freeze plugs or replace the blocks drain plug with one.

 

[hubs97xj]

Found oil in the driveway today while looking for coolant. Yay. More maintenance projects.

No idea on the valve cover, but it's leaking currently. I may attend to the oil leak first- if I do I'll have a look at that bolt- that would be pretty close to the controller, and up away from the exhaust and anything that might thrash the wire (one less part, 2 less connections in the cooling system- that's a plus). Don't know about clearance though, and I can't get an answer on the proper size of the FAL sender (3/8" threads on sender, adapter made specifically for said sender has a 1/4" bung- surely they can't be serious. 1/4" threads with a 3/8" adapter would make more sense, but who knows)

Buy parts, drink beer, figure out how to make parts work, put parts on. I don't know why I expect shtuff to go together easily- I should know better by now.

Thanks for the thoughts, I've at least got a workable plan and some alternatives now.

 

[Blaine B.]

Can you possibly find a sensor that would take the same thread as the coolant temp sensor in the thermostat housing, and find some sort of a "T" fitting with 2 female ends and 1 male end? That would seem ideal.

 

[RichP]

Can you possibly find a sensor that would take the same thread as the coolant temp sensor in the thermostat housing, and find some sort of a "T" fitting with 2 female ends and 1 male end? That would seem ideal.

The problem is that the sensor has to be in the coolant flow, not in the air above it, the more directly in the flow the more accurate the readings. Think a thermometer on your skin vs one inside your mouth, the one in the mouth is more accurate. Any air thats in the system will end up in that T fitting.
To me, if you want an accurate block coolant temp, the drain plug on the drivers side would be the best bet, no holes to drill, just remove the plug and screw in a sensor, done. The only downside I could see would be it's proximity to the headers.

 

[sjkimmel99]

Remember that coolant flow is in through the pump, past the cylinders, up through two relatively small holes in the back of the block/head, then forward through the head and out the t-stat housing.

The main passage for coolant from the block to the head are the two oblong holes to the right of the exhaust port here.

The head gasket blocks the rest except for some relatively tiny holes in the gasket where the triangle shaped holes in the head are. A sensor in the block isn't going to tell you what the max heat of the engine is the same way a sensor at the t-stat housing or in the top hose will.
Someone will observe that the factory gauge sensor is at the back of the head and doesn't show the output temp of the coolant either. Don't know why they put it there, maybe an average temp(?) Besides they put the computer sensor at the front of the block so if it's good enough for the computer it's good enough for the rest of us.

 

[ehall]

The resistance on the gauge sender is such that it is more or less accurate

Doesn't matter where it is really, as long as the resistance is correct for the location

 

[RCP Phx]

The resistance on the gauge sender is such that it is more or less accurate

Doesn't matter where it is really, as long as the resistance is correct for the location

What?Cant wait to here you explain this?????

 

[hubs97xj]

In this particular case, I'm not going to be using any of the stock circuitry, so I only need a sender with the same resistance (range) as the probe the controller currently uses.

If I were to relocate my stock sender, I would probably see higher or lower temps, depending on where I put it- and they might not reflect the actual coolant temperature- in that case, finding a sender with a different resistance would be a simple way to correct the displayed temp on the gauge, if I'm correctly understanding how the stock system works.

I'm only on my second cup of coffee, so I might have this all wrong.