Koso slim water temp gauge install

[Hornd]

Hornd

I would advise you to change your temp sensor location to the other side of the engine:

this is a "reverse flow" system, it puts hot water into the bottom of the radiator and cool comes out the top. Why Toyota did this? not really sure, but maybe to reduce the chance of getting burned if you touch the upper rad tank.

The result: your temperature will be reading at the lowest temperature in your system (right after it's cooled down from the radiator) and is not very helpful in indicating an overheat condition since you don't know the actual temperature of the coolant coming out of your engine.

What makes it reverse flow?

 

[baldilocks]

Hornd

I would advise you to change your temp sensor location to the other side of the engine:

this is a "reverse flow" system, it puts hot water into the bottom of the radiator and cool comes out the top. Why Toyota did this? not really sure, but maybe to reduce the chance of getting burned if you touch the upper rad tank.

The result: your temperature will be reading at the lowest temperature in your system (right after it's cooled down from the radiator) and is not very helpful in indicating an overheat condition since you don't know the actual temperature of the coolant coming out of your engine.

.
I think you need to research this subject and get back to us. I'm sure you will find out that the 1fz coolant flows from the top down.

 

[baldilocks]

What makes it reverse flow?
View attachment 1473392

Last night I was without access to my fsm so I searched the net for this diagram but never did find it. Good post!

 

[half k cruiser]

Hornd

I would advise you to change your temp sensor location to the other side of the engine:

this is a "reverse flow" system, it puts hot water into the bottom of the radiator and cool comes out the top. Why Toyota did this? not really sure, but maybe to reduce the chance of getting burned if you touch the upper rad tank.

The result: your temperature will be reading at the lowest temperature in your system (right after it's cooled down from the radiator) and is not very helpful in indicating an overheat condition since you don't know the actual temperature of the coolant coming out of your engine.

The location pictured on the first page of this thread is the best location for your temperature sensor. The hottest water is coming out there, not from the lower port near the thermostat.

 

[Woofythewolf]

I am completely wrong!

I'd thought that the water came out from behind the thermostat so the thermostat would get the hottest coolant to trigger it to open and close, while the water bypassed it by leaving through the heater hose to get warm water to it when first warming up.

Now I see that it's the exact opposite, the cool water comes in, while hot water from the heater goes in to activate the thermostat.

Edit: that's a really handy diagram, makes me want to spend more time with the FSM

 

[Steve D]

What makes it reverse flow?

That's a relief. My sensor is in the top rad hose, making me worry if those were the "after cooling" temps I was seeing!!

 

[rc51kid]

Has anyone ever had the feeling that their Koso water temp gauge was reading high, like 10-15 degrees high? Many times when I compare the Koso reading with my hand held infrared thermometer, the Koso is a good bit higher. And that's taking both readings at the Koso temp sensor location in the water outlet pipe.

I have a new HG, O2 sensors, no codes and a fully overhauled cooling system including a modded fan clutch and when it's 100 degrees outside with AC running, I can see 210-215 fairly easily on the Koso when running at highway speed. Shut down the AC or come up to a slow down in traffic flow and the water temp drops.

So I have been wondering which gauge I should believe, infrared or Koso?

Yes kind of. New oem coolant systen and oem hg. Runs great with great temps...but just a little high.

Some times i think about it. I use the tubing in the coolant line going to the rad. Some times i think the inside id is smaller. Smaller id would increase presser. Increase pressure would increaae temps in theory. But that is very much in theary.

Mostly now that i have a new oem coolant system i dont look at my koso except at timea on the trail.

 

[baldilocks]

Yes kind of. New oem coolant systen and oem hg. Runs great with great temps...but just a little high.

Some times i think about it. I use the tubing in the coolant line going to the rad. Some times i think the inside id is smaller. Smaller id would increase presser. Increase pressure would increaae temps in theory. But that is very much in theary.

Mostly now that i have a new oem coolant system i dont look at my koso except at timea on the trail.

I believe that your theory on pressure is incorrect. The other day I stared my cruiser up in the morning and watched both, the Koso and the infrared temps.
At the outset both read the same, ambient temps. As time went by, the Koso gauge rose faster. When Koso said 100 I the outlet pipe from the head, the infrared said 75-80. When the koso read 135-140 my fingers knew that that the water in the outlet pipe was way too hot for me to swim in, yet, the infrared thermometer read about 100-105 which is a jacuzzi temp. By the time my Koso gets to 200 with AC running and maybe climbing a grade onthe high way, if I pull over and compare gauges, the infrared will read something like 185-187. Last summer it was 100 degrees out and at 70 mph my Koso crept up to 219 but the infrared was still a little below 200.

I want to believe the lower reading of the infrared but, based on my warm up process findings, I am inclined to believe the Koso.

Perhaps my infrared thermometer has become inaccurate. I need to do a controlled test of it.

 

[Woofythewolf]

Don't forget that the hoses etc are insulators, and that they have air blowing on them to cool the outside surface (which is what the IR gun reads)

You can check your probe in The temp range it gets used at by sticking it in boiling water and see if it reads 212*F (make sure to adjust for altitude) when the water is boiling

Edit: helps if you have a camp stove or something to boil it next to your truck so you don't have to unplug everything (and get a plug for the hole you drilled)

 

[Steve D]

Some times i think the inside id is smaller. Smaller id would increase presser. Increase pressure would increaae temps in theory. But that is very much in theary.

Pressure inside a closed system equalizes in all areas of the system.

 

[Dragos80]

Really cool mod, but I am not a big fan of cutting into anything, especially a coolant line on a 1FZ-FE.
I chose to use Torque with bluetooth OBD2 transmitter. It gives me a few other parameters to monitor, plus fault codes.

 

[Steve D]

The Koso works better for OBDI though.

 

[half k cruiser]

Really cool mod, but I am not a big fan of cutting into anything, especially a coolant line on a 1FZ-FE.
I chose to use Torque with bluetooth OBD2 transmitter. It gives me a few other parameters to monitor, plus fault codes.

The mod was never really intended for OBDii trucks. Also the way I detailed it was to tap the upper water pipe elbow, not splice into a hose. For whatever reasons lots of people doing the mod seem to like the splice method.

 

[baldilocks]

It's like that boss on the water outlet was intended for an additional temp sensor.

Everyone considering this modifications NEEDS to know that the Koso sending unit threads are BSPT not the usual NPT. I made that mistake while the correct tap sat right there in my tap kit box! I installed the sender with plenty of grey permatex and a year later there are no leaks.

 

[Hornd]

It's like that boss on the water outlet was intended for an additional temp sensor.

Everyone considering this modifications NEEDS to know that the Kose sending unit threads are BSPT not the usual NPT. I made that mistake while the correct tap sat right there in my tap kit box! I installed the sender with plenty of grey permatex and a year later there are no leaks.

I had no idea it was not NPT. Guess I did the same.
Done right that Boss is not leaking.
I'm 10X more worried about the Pesky Heater Hose & Rear Heater Lines.

 

[Woofythewolf]

Just finished installing my $7.99 guage! Also I did it with no drilling or tapping, or using a hose coupler one. (and entirely from parts from my local OSH except the temperature guage kit itself).
DIGITEN 12V Red Digital Fahrenheit degree Thermometer High Low Alarm -76-257F Temperature: Amazon.com: Industrial & Scientific

have yet to take it for a drive though. I'll update when I do.

cooling system specs: new koyo 1917 3 row copper radiator, aisin blue hub fan clutch with 10k cst fluid, freshly flushed engine with zerex super radiator cleaner (the one where you get rid of ALL the antifreeze, and run it and distilled water for 3-6 hours of driving time).

How: use the air bleed line to put your sensor in (more on the sensor later). AFAIK (and according to the diagram above) the little tube coming from right before where everyone is putting their sensor is to bleed air from the cylinder head allowing coolant to take it's place while you fill your system.
Originally, I wanted to use a coupler in the middle of this hose and my sensor in that. However, I realized that since the flow through this hose is basically nonexistent (thanks to a giant hose that's much easier to go through), it wouldn't be getting an accurate reading of water fresh out of the engine.

So I made this:

basically it's a 5/16" brass nipple with a 3/16" OD brass tube JB welded inside (make sure you use the one rated to 550*F)
then I stuck the thermistor through that (again filling the tube with JB weld) so it just barely poked through the end.
Then I used some liquid electrical tape to make a boot for the wire (to gently flex it away so it doesn't become like an old iPhone cord with the end tearing off).
Mine was a tad short, I would recommend making the tube with the sensor stick out 2 1/4"-2 1/2" from the nipple.

Then to install: cut line about the length of the nipple beyond the nipple of the aluminum output port (you can see I cut mine about 1/4" too short, but I already had it on 3 rings so I'm satisfied). Then push this in all the way in until the nipple hits the other one of the engine side, and secure it with a hose clamp. be sure to plug the other end (the end on the radiator) as well.

Basically, the brass tube with the thermistor in the tip extends into the flow of water by about 1/8" inch so it gets an accurate reading.


Since mine blocks the bleed line, you have to undo a hose clamp and pull it off whenever you do A drain/refill (anything that takes the coolant level below the level of the cylinder head) so that the air can escape as designed.

I calibrated mine to a glass of icewater (you can calibrate and set a top and bottom alarm on this unit) but I may do it to boiling water later to make sure it's as accurate as possible (calibrating it close to the temperature it operates at).

EDIT: back off the nipple 1/16" of an inch so they don't touch. Brass vibrating/moving against steel may create tiny particles that probably aren't good for your water pump)

 

[mypancreasbroke]

Just finished installing my $7.99 guage! Also I did it with no drilling or tapping, or using a hose coupler one. (and entirely from parts from my local OSH except the temperature guage kit itself).
DIGITEN 12V Red Digital Fahrenheit degree Thermometer High Low Alarm -76-257F Temperature: Amazon.com: Industrial & Scientific

have yet to take it for a drive though. I'll update when I do.

cooling system specs: new koyo 1917 3 row copper radiator, aisin blue hub fan clutch with 10k cst fluid, freshly flushed engine with zerex super radiator cleaner (the one where you get rid of ALL the antifreeze, and run it and distilled water for 3-6 hours of driving time).

How: use the air bleed line to put your sensor in (more on the sensor later). AFAIK (and according to the diagram above) the little tube coming from right before where everyone is putting their sensor is to bleed air from the cylinder head allowing coolant to take it's place while you fill your system.
Originally, I wanted to use a coupler in the middle of this hose and my sensor in that. However, I realized that since the flow through this hose is basically nonexistent (thanks to a giant hose that's much easier to go through), it wouldn't be getting an accurate reading of water fresh out of the engine.

So I made this:
View attachment 1478608
basically it's a 5/16" brass nipple with a 3/16" OD brass tube JB welded inside (make sure you use the one rated to 550*F)
then I stuck the thermistor through that (again filling the tube with JB weld) so it just barely poked through the end.
Then I used some liquid electrical tape to make a boot for the wire (to gently flex it away so it doesn't become like an old iPhone cord with the end tearing off).
Mine was a tad short, I would recommend making the tube with the sensor stick out 2 1/4"-2 1/2" from the nipple.

Then to install: cut line about the length of the nipple beyond the nipple of the aluminum output port (you can see I cut mine about 1/4" too short, but I already had it on 3 rings so I'm satisfied). Then push this in all the way in until the nipple hits the other one of the engine side, and secure it with a hose clamp. be sure to plug the other end (the end on the radiator) as well.
View attachment 1478609
Basically, the brass tube with the thermistor in the tip extends into the flow of water by about 1/8" inch so it gets an accurate reading.


Since mine blocks the bleed line, you have to undo a hose clamp and pull it off whenever you do A drain/refill (anything that takes the coolant level below the level of the cylinder head) so that the air can escape as designed.

I calibrated mine to a glass of icewater (you can calibrate and set a top and bottom alarm on this unit) but I may do it to boiling water later to make sure it's as accurate as possible (calibrating it close to the temperature it operates at).

EDIT: back off the nipple 1/16" of an inch so they don't touch. Brass vibrating/moving against steel may create tiny particles that probably aren't good for your water pump)

Hhmmm, nice! Interested in your results after driving. It seems that air bleeder location is pretty ideal for not having to cut/tap anything. I still want to install a real time temp gauge into my 94, and maybe this will be the way I finally go (after my AC is back together, front control arms and sway bar are replaced, hood and front fender replaced, etc, wrecks are fun!)

 

[Woofythewolf]

good: I can accurately read the temp.
Bad: it's only when the fan clutch isn't engaged and blowing air over it.

basically, the very thermally conductive jb-weld I used to attach the sensor, and the long brass tube that's in the full airflow of the fan means that it reads low by 4-5*C on average. This is greatly aided by the fact that the probe isn't long enough to stick all the way into the coolant flow. (I did calibrate it in boiling water, it was to within .5*C)

when I turn the engine off, the temp creeps up to a little bit above the thermostat opening temperature (right where it should be with a brand new 3 row copper rad, new oem thermostat, and 10k fan clutch)

I'm going to make another sensor that's about 1/2" longer so it actually sticks into the coolant, and maybe just stick a 1" heater hose over the whole sensor to block the airflow from the fan.

EDIT: I have a 5 pack of sensors coming from amazon and they should be here on monday.

 

[Steve D]

For whatever reasons lots of people doing the mod seem to like the splice method.

I liked the fact that I had a spare hose on hand so this mod was easily reversible.

I thought the 1FZ doesn't have an air bleeder but bleeds itself through the overflow tank? My truck is in Colorado so I can't go out and look at where @Woofythewolf tapped his sensor in.

 

[Woofythewolf]

I liked the fact that I had a spare hose on hand so this mod was easily reversible.

I thought the 1FZ doesn't have an air bleeder but bleeds itself through the overflow tank? My truck is in Colorado so I can't go out and look at where @Woofythewolf tapped his sensor in.

It's not really that kind of bleeder.

Basically the main hose dips down to go under the distributor cap, which leaves the entire cylinder head as a giant air pocket (The inlet also slopes down to the lower rad hose too of course). This hose allows air to escape that giant air pocket and escape into the top of the radiator while you fill it. (starting the truck with almost no coolant in the head could cause hotspots and other bad stuff)

EDIT: it's the little hose that runs parallel to the main output hose in Hornd's diagram.