Manual temp guage location

Real quick ....
I want to switch my ele operated temp guage to a manual temp guage.
Where can I put the sender for the manual guage?
Its a 91, 4.0.
(yes ... i searched. no luck)

On the driver's side of the block, about halfway down and halfway back, there's a recessed drain plug for the cooling system. With an appropriate reducing adapter you could put the sender there and not disturb any of your original equipment.

Or if you want to abandon the factory gauge, the sender is in the left (drivers side) rear corner of the head.

Eagle said:

Or if you want to abandon the factory gauge, the sender is in the left (drivers side) rear corner of the head.

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I knew about that one, just put a new sender in it.
Aint that hole a little small for the new sender for a manual guage ?

The left/rear cylinder head hole is threaded 1/8 NPT, I believe, and you should be able to get a sensor with that thread.

However, that's generally for RENIX - while I'm not doubting Eagle (I'd not be surprised if he's got a 91 to look at - are you back home yet?) you might want to have a look at the thermostat housing. If you have the old style without a sensor, you can install a newer thermostat housing, and that will have a hole threaded 3/8"NPT - which is far easier to find a sensor for.

Remember that you should get the sensor down into free-flowing coolant, if you have the probe in a "pocket," you will NOT get accurate readings! If you have trouble with the cylinder head hole or the termostat housing, you can get a sleeve that you can split into the upper hose and it has a threaded bung that will accept a sensor.

Again, it is important that the sensor tip is inserted into free-flowing fluid, if it's in a pocket, it's going to give you inaccurate readings. The OEM sensors are generally installed in good locations.

If there is a sensor already in the thermostat housing, you should probably not replace it. I don't know offhand what it's there to do, but it's not something that should be replaced that I can think of...

5-90

Yup.... I got a sensor in the t-stat housing. Just replaced it too.

5-90 said:

you can get a sleeve that you can split into the upper hose and it has a threaded bung that will accept a sensor.
-90

Click to expand...

UHHHHHHHH ........... Where?
This sounds like the "easiest way" ( for me ) and just leave the stock guage alone.

Check Summit or Jeg's - I know I've seen them in there. I don't think they cost too much, and all you have to do is get one for the ID of the upper hose (the lower hose will also give you a false reading, since it's the outlet from the radiator.

You can measure the radiator outlet for your hose ID - and just plumb the fitting into the hose right before the radiator - this will be easiest, and will also keep the fitting from rubbing up against anything - like the AC Compressor.

As I recall, you're going to have to cut out about an inch and a half of hose to do the job - just make sure you do a nice straight cut, and you'll be alright.

5-90

5-90, the man said he has a '91. So his temp gauge is fed from the head, and his ECU receives date from the t-stat housing.

Drifto, are you asking if that hole in the block is too shallow for the probe on the mechanical gauge? Dunno, I never looked at it with that idea in mind. If I've pulled that plug, it was usually closely followed by a stream of hot coolant.

But I suspect that it's large enough that you could thread in a reducing adapter to space the sender out a bit. What brand of gauge will you be using and what's the thread on the sender?

Eagle said:

5-90, the man said he has a '91. So his temp gauge is fed from the head, and his ECU receives date from the t-stat housing.

Click to expand...

Like I said - you probably have one to look at - I don't. That's why I wasn't sure - and I didn't feel like looking it up (since my OEMR catalogues are all on a CD buried in the other room...)

I guess, then, that the cylinder head temp sensor was deleted sometime around 1996, with the advent of OBD-II? Just trying to make sure...

The problem with the "spacer" idea is that you'll create a "pocket" in the flow of coolant, which means that the sensor will have either lagging readings, or totally false ones.

Doing the "radiator hose" mod makes sure you can get constant flow over the sensor tip, which means your readings will keep up with what's really happening and you won't get "delayed notification" or find out you're overheating when you see the steam...

5-90

5-90 said:

I guess, then, that the cylinder head temp sensor was deleted sometime around 1996, with the advent of OBD-II? Just trying to make sure...

5-90

Click to expand...

I believe it was '97

I was looking into doing the manual gauge also to replace the idiot light..he he. BUT all the guages i found that would plug into that location were at minimum 1/4 npt...WAY TOO BIG!! Or I and the guys at the parts house are both idiots?? We pulled a sensor off the shelf to compare thread size also.

If someone has a link to the hose splice in sensor adapter part...please post it, that is what i will do. Hate to cut up a new coolant hose, but for a great cause and prevention of overheating, will be worth every bit.

Cory

I took a quick look when I did that last post, but I didn't spot anything in a couple minutes. Don't have the new paper catalogues in, or I'd peruse them.

This is something I've seen available from most hotrod houses - so Summit, Jeg's, RB's, and others are all possibles.

If you have a source for parts handy and you're in a hurry, you can actually MAKE one yourself - you just make/buy some sort of coupler and do whatever you have to do to thread it (f'rinstance - braze a threaded bung on the side of a piece of copper tube that fits into the hose - if you feel your torch work is up to the task...)

Check around - I'm not exactly sure what it's called, but I know they're out there!

5-90

Thanks guy's.
Iam gonna see what Summit has to offer in the way of the "hose mod".

drifto77 said:

I knew about that one, just put a new sender in it.
Aint that hole a little small for the new sender for a manual guage ?

Click to expand...

That's what mine looks like. The hole that I took the sender out of (driver's side rear of head) hasn't a chance of letting the "bulb" from my sunpro temp gauge fit thru it. Now what? not sure I want to do the "in the rad hose deal" Would the drain plug that Eagle talked about in his post have the flow around it necessary to have the gauge work correctly?

Thanks

No reason why not. You'd be reading flow at a lower point in the block, but I've never seen a block drain that was cast into a "pocket" - too much work and makes the cores funky.

I don't know what the thread on that hole is, but if the plug is anything like mine, you'll need an 8mm square drive to get it out. You can make one pretty quick using an 8mm hex key and either a die grinder or a bench wheel - in about two minutes. Grind carefully!

5-90

If you are still looking for the radiator hose mod to put the temp gauge sending unit, go to Jeg's, type in "petcock tube" in their search bar, its under "universal petcock tubes" toward the bottom. Couldn't you just take out the petcock and install the sending unit in it's place? They have straight and 60* angled tubes in 1.5" & 1.75". What is the I.D. of the top rad hose for a 95 XJ 4.0, anybody know?

I could probably just make one too, but, costs me beer now since i no longer work at the shop...he he. I will look around.

Cory

5-90 said:

Doing the "radiator hose" mod makes sure you can get constant flow over the sensor tip, which means your readings will keep up with what's really happening and you won't get "delayed notification" or find out you're overheating when you see the steam...

5-90

Click to expand...

5-90,

I think the upper rad hose idea is not the best. The only time that you'll get accurate readings is when the tstat is open. The better idea would be to tee off of the heater hose. There is always coolant flowing through those(before the heater valve if you have one).

K

hotrod22 said:

If you are still looking for the radiator hose mod to put the temp gauge sending unit, go to Jeg's, type in "petcock tube" in their search bar, its under "universal petcock tubes" toward the bottom. They have straight and 60* angled tubes in 1.5" & 1.75".

Click to expand...

WOW ! ! $30.00, Think I can make one for less.

hotrod22 said:

Couldn't you just take out the petcock and install the sending unit in it's place?

Click to expand...

Think the bung is the same size? (after you pull the petcock and the adapter)

Still not entirely true.

It would be best to pick up coolant temperature inside the block, probably just before the thermostat, but that's not always doable.

However, picking up the lower hose gets radiator outlet temperature (false low,) and the heater hoses aren't always flowing (remember the control valve?) so that won't be as consistent either.

The upper hose is a compromise - while you won't get useful readings until the thermostat opens, you will get good readings once it does.

Given a choice, I'll put it in the block - if anyone pulls that drain plug, please tell me the thread size. I've not gotten around to pulling one out yet - just haven't had a real need to dork around with the thing (even though I have made a couple 8m/m square drive keys.)

The only real problem with the "upper hose" mount is that you won't get a reading if the thermostat freezes shut - but there are also audible clues to an actual overheat. Also, if anyone can find a useful part number for the Stant "Fail-Safe" thermostats (the freeze OPEN when they fail!) please do post them. I'd like to see them in use, since it's a good idea.

Also, you'll get useful readings if you happen to run without a thermostat (not generally recommended, but it is doable,) and that's still a workable solution.

If you are going to plumb in a thermal sensor into the heater hose, it would probably be best to tee it off the heater supply line off the water pump - at least that way, there would be some activity around the sensor. It is critical to have constant or near-constant flow over a thermal sensor to get an accurate reading - putting it in any sort of "pocket" where the flow is hindered is simply asking for false readings, and looking for trouble. I don't look for trouble - it finds me with alarming regularity...

5-90

corbinafly said:

5-90,

I think the upper rad hose idea is not the best. The only time that you'll get accurate readings is when the tstat is open. The better idea would be to tee off of the heater hose. There is always coolant flowing through those(before the heater valve if you have one).

K

Click to expand...

5-90 said:

the heater hoses aren't always flowing (remember the control valve?) so that won't be as consistent either.
5-90

Click to expand...

Actually the heater hoses before the control valve ARE always flowing. The control valve just redirects the flow back to the pump in order to bypass the heater core when the heat is off. Next time you have the opportunity, take a look at one when it's out of the vehicle. It'll be clear as day how it works.

So the coolant always flows out from the tstat housing to the control valve, then to the heater core or gets bypassed, then back to the water pump where it is again pushed through the head.

K