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I bought a temperature gauge from Jaycar Electronics for $39


It displays from -50 to +150 degC and has both high and low alarms, has a suction cup on the back and can also be panel mounted

Anyway, i cable-tied the sensor to the top radiator pipe in my Outback to see how it went.

The results were as follows (with a 10deg ambient temp)

Start temperature - 9deg
5 minutes later - 40deg (car temp gauge just below half way)
For the rest of the journey the temperature varied between 63deg while cruising at 100kmh, and 69deg when below 70kmh.
The only time the temperature rose above that was when i was stopped.
At 80deg the thermofan kicked in.

Do those temperatures seem a little low, as the FSM states that the thermostat starts to open at 76-80deg and is fully open at 91deg.



Discuss... Ask questions... Comment.

Im willing to do tests on request too (within limits)

I'd say that's a bit low. Most healthy engines I've looked at run between 85-95 deg.

Cable tying the probe against a hose mightn't be getting real good conduction. Could you slip the probe into the end of a hose so it's in coolant? Or maybe back off a bolt somewhere on a cylinder head and then clamp the probe under it?

You can also test the gauge in a pot of water on the stove. Water bubbling = 100 degrees C.

Dane.

The probe is cable tied to the metal part of the pipe and there is foam wrapped over the top of it.

The engine has a new thermostat, but the guy who was helping me when i put it in suggested i remove the giggle pin from it. Could it be letting too much water through?

Is your factory temp gauge showing anything different since the thermostat change?

Do you have another thermometer to check it against? I got a Fluke digital IR thermometer recently - pricey but worth it for fault finding.

Dane.

The Jiggle Pin on the newer thermostats is only there to reduce the chances of airlocks in the cooling system. If removed will not increase flow enough to make it run cooler. I would say that looking at you car's temp gauge that all is good and it's because the probe is not immersed in coolant. The metal on the outside of the radiator will be cooler than the coolant on the inside. I would try and fit the probe into the top radiator hose (bit of silicone either side of the probe to stop leaks), this is the hottest part of the cooling system and will be very close to where your factory temp sender is.

Discuss... was about to go buy another $149 watchdog unit ..... the temps you are getting seem about the same as I get mith my 'dog. In shed the start up temp about 8 degrees, cruising at 80 to 100kph as low as 63 C , it used to be 71C on this engine before I redid the head gaskets and have since leaned the mix a bit more LPG. I set my alarm to go OFF at 88C. Used to use 86C but that would go off on start up after sitting a short time. Thermo fan comes on at 84 or 85 C

When I was using crack fixer was running at 104 to 109 oops and gauge was still only at three quarters! Love to see what these read when you ashley frqanengine from overheat. Have seen VL turbo that went this way , even the injector tips had that range of rainbow colours you look for when hardening steel - brown blue purple


POWER SUPPLY is long life battery ? ( I no look at your link at this stage) the 'dog connects to car power

You could make a metal probe holder and make a hole in it to use a thermostat bolt on EA style , EJ's ? they got plastic bolts as well as thermo housing ? cheeky

Top radiator hose? Rubber ? Rubber does get hot as, yeah, get another one and attach it to metal of engine and compare .... you ask if they sound too low ?? Don't recall seeing any specs for temp of rubber hose even metal temp of the block may differ as most people have experience of water temp - not saying, but there may just be a difference between metal, rubber and water all in the same engine

all cars shoul have something this simple -the memory for high or low reading beats those warranty washers engine reco places and wreckers stick on heads and engines, get too hot they lose the soler in the middle - goodbye to warranty

I have the probe (metal stake about 3mm in diameter and about 50mm long, as pictured above) cable tied to the metal top pipe just before where the rubber hose starts. I also have some foam wrapped over the top of it so air off the radiator doesnt affect it.

I will try putting the probe in a cable crimp lug and bolt it to something.

In the FSM, it states that the first thermofan comes on at 95 deg and the 2nd one at 100 deg (if the air con is on)

My thermo fan came on at 80deg so maybe there is 15 deg of error in my themometer.

Yes the battery is a long life lithium button cell, which is ideal as the temperature can be seen at all times and it keeps the memory for the min and max temp.

My only quibble is that the buttons are on the back, and if i were to permanently mount it, the buttons would be acceptable.

One possible cause for the lower readings could be from when i lengthened the cable. I didnt solder the join because i thought it was a thermocouple, and dissimilar metal joins can effect readings, but i have since found out that it uses a NTC thermistor, so a high resistant joint could cause issues. I'll resolder it and see how it goes

More testing to come

What you are doing will never give you an accurate reading. The probe is useless. Although you could use it to measure the temp of a roast chook.

To accurately measure the water/oil/gearbox, or any other liquid you want to measure, the probe needs to be immersed in the fluid.

if you understand ntc's you could possibly make a sender up to fit the jaycar gauge if not,

Go back to Jaycar get your money back and get a proper VDO/Autometer/StewartWarner gauge and the right gauge sender OR fix the original one.

cheers

One drawback I see is that it times off after one hour.

2Grumpy - do any of your suggestions set off an adjustable alarm.

Think there is an association between metal temp and water temp but not same reading. Afterall, it is the metal that gets hot first and water absorbs it carries it away to cool. Even if you fitted a new fan switch sensor from Subaru you may still find metal temp is different to spec temp for switch. Use it as a guide in relation to water temp gauge.

[quote="steptoe"]

2Grumpy - do any of your suggestions set off an adjustable alarm.

/QUOTE]


Bosch make a heap of sensors that set off either an "IDIOT" light or a buzzer. I think if you ask around you should find one. Might need to T join it with the factory sensor or drill and solder the sensor to the radiator.

You could also use the Jaycar kit KC-5381 on page 39 2010 cattle dog, I guess the relay will switch on at what ever temp you set it at, if you can work how to get the NTC into the water.


cheers

Temp sensor has been tested with a kettle and proven accurate



So the issue is conductivity between the top metal hose and the probe, so i will modify it so it is in the water path and see how i go

steptoe wrote:One drawback I see is that it times off after one hour.

Not on this one, is has been on continuously since Sunday

steptoe wrote: Even if you fitted a new fan switch sensor from Subaru you may still find metal temp is different to spec temp for switch.

Not in the EJ's, their thermo fans are controlled by the ECU

Grumpy wrote:What you are doing will never give you an accurate reading. The probe is useless. Although you could use it to measure the temp of a roast chook.

To accurately measure the water/oil/gearbox, or any other liquid you want to measure, the probe needs to be immersed in the fluid.

if you understand ntc's you could possibly make a sender up to fit the jaycar gauge if not,

Go back to Jaycar get your money back and get a proper VDO/Autometer/StewartWarner gauge and the right gauge sender OR fix the original one.

I think you are being a tad negative, I bought this for a little bit of experimentation and fun. If i wanted something professional, i would have bought a professional one.

My plan is to have several NTC sensors and a multi selector switch so i can choose between several readings, like coolant temp, head temp, transmission temp ect. This is not for my Outback, its for my RX

Some may be missing the point here too - some of these temp gauges NEED water on them to give a reading. By monitoring metal temp gives warning of metal getting too hot. IF somehow you lose all your water in a hurry the temp gauge may not be seen rising or not even rise defeating its purpose - this is the basis of the watchdog temp alarm I have. Alerts differences vry early in the scheme of things. I lost 500ml of watrer and noticed a 5 degree rise was suss saved me engine there I reckon - two engines actually.

Suparoo wrote: I think you are being a tad negative, I bought this for a little bit of experimentation and fun. If i wanted something professional, i would have bought a professional one.

Sure, I might sound a "tad negative" but you made no indication that it was for fun. I wouldn't use or trust the setup as you described on my lawn mower.

If someone else reads this post and thinks it's a good idea to copy it, I think they should be warned before it costs them a new motor.

Does the display indicate higher than the 99.9 degress shown in the photo? Water temp may exceed that temp.

steptoe wrote:Some may be missing the point here too - some of these temp gauges NEED water on them to give a reading. By monitoring metal temp gives warning of metal getting too hot. IF somehow you lose all your water in a hurry the temp gauge may not be seen rising or not even rise defeating its purpose - this is the basis of the watchdog temp alarm I have.

You are very correct. Temp sensors need to be immersed to work, they generally won't indicate a loss of water. My neighbour tore the bottom hose clean off his cruiser. There was no warning until the engine needed a new $3000 head and rebuild.

I had one of those with the probe poked thru the hose between the throttle body and intercooler on my B4, reading intake air temp after turbos and intercooler. Worked really well in that application.
I also had a cheap Speco temp gauge with the sensor mounted in one of those alloy temp sender "pipes" in the top radiator hose (This link shows what i mean Eeeew, Nissans). Also worked well, was accurate compared with when the fans came on.

2Grumpy , it says u to 150 C I think in specs. I trust my 150 dollar watchdog HEAPS, it also has a wire to connect to an oil idiot switch

2Grumpy wrote:Sure, I might sound a "tad negative" but you made no indication that it was for fun. I wouldn't use or trust the setup as you described on my lawn mower.

If someone else reads this post and thinks it's a good idea to copy it, I think they should be warned before it costs them a new motor.

Does the display indicate higher than the 99.9 degress shown in the photo? Water temp may exceed that temp.

You are right, i didnt actually mention it was for fun, but i did say

Suparoo wrote: i cable-tied the sensor to the top radiator pipe in my Outback to see how it went.

Not really a permanent install, and this little test proved that metal to metal contact isnt sufficient for proper heat transfer.

My plan is to install it somewhat like the link that Squishy posted.


Maybe there wasnt enough contact between the pipe and the sensor, because i would have thought that that piece of pipe, with 100l/min flowing through it would be reasonably close to the water temp, being aluminium, its a very good conductor of heat.

Im gonna try crimping the probe in a cable lug and bolt it with some thermal paste, to see if it works better

steptoe wrote:Some may be missing the point here too - some of these temp gauges NEED water on them to give a reading. By monitoring metal temp gives warning of metal getting too hot. IF somehow you lose all your water in a hurry the temp gauge may not be seen rising or not even rise defeating its purpose - this is the basis of the watchdog temp alarm I have. Alerts differences vry early in the scheme of things. I lost 500ml of watrer and noticed a 5 degree rise was suss saved me engine there I reckon - two engines actually.

I to have a watchdog and am happy to pay $140 i didn't have one on my l-series
It blew the small hose above the water pump and cost me an engine
It was well and truly stuffed the temp gauge was a tad over 1/2 it had no water to measure the temp
I put my prob on the head close to the block it doesn't matter where on the engine as long as you monitor it for a week then put your high alarm about 5 degrees above the highest of that week
Nothing worse than having to keep an eye on your gauge when 4wding
The other thing is you know before it gets too hot the worst i have had is 91 degrees average 84 degrees

Jan

On the topic of discussing coolant temps in general.

I got a Speco mechanical temp guage off fleabay last week. Works a treat. Fit the probe down the top hose with some bluemaxx. I was getting 80-90 cruising around and 95-105 while at 110kph. The temp went down to at or below 100 when i put the second fan on which i thought was a lil strange.

(I have an EJ22 L series with ali L series radiator)