More Thermostat/Temp Gauge nonsense

[d90rover]

So I had the typical temp gauge reading low, barely 2-3 needle widths into the white arc. And following thread searches, I assumed it was a missing/misaligned top gasket. So I gathered a new 190 deg stat, top and bottom gasket and figured no problem. So upon disassembly I discovered the top housing was pretty badly corroded as seen in the pics. So I assumed even with a new top gasket, enough coolant would leak past, and ordered a new top housing. After reassembly however, same symptoms, 2-3 needle widths into the white arc. SO either I have the coolest running LC in Arizona, or it's something else. Temp sensor? Gauge itself mis-calibrated? What's next to check?

 

[Seth S]

How hot is the air coming from the heater when the truck is warmed up and the heater set to the warmest setting?

 

[chichiflys]

Maybe get a $13 laser temp sensor and do some readings on the upper and lower hoses, etc. as a backup? How's the wire connection at the sensor, clean?

 

[g-man]

you can ohm test the sender. should be 226 ohms (+33.6/-36.6) at 122 deg. F, and at 239 deg F ohms are 26.4 (+1.71/-2.21) Just pull the wire of the sender put the pos. probe on the sender and the neg on any ground. Also you can test the gauge 3.5 volts, 55 ohms. to do this unplug the sender. Probe the back of the gauge with the ignition on and ground to a body ground. Also you can ohm test the wire from the sender to the gauge. Find this info on 84 body manual pg BE35 and BE36. BE= body electrical

 

[d90rover]

you can ohm test the sender. should be 226 ohms (+33.6/-36.6) at 122 deg. F, and at 239 deg F ohms are 26.4 (+1.71/-2.21) Just pull the wire of the sender put the pos. probe on the sender and the neg on any ground. Also you can test the gauge 3.5 volts, 55 ohms. to do this unplug the sender probe the back of the gauge with the ignition on and ground to a body ground. Also you can ohm test the wire from the sender to the gauge. Find this info on 84 body manual pg BE35 and BE36. BE= body electrical

Thanks for the next steps!

 

[NeverGiveUpYota]

Replacement temp sender is really easy to swap out too... check the wiring to it as well as the clip. My wire was cracked just at the bend and I was getting poor readings. Easy to cut and crimp a new female fitting on it.

 

[Spike Strip]

The stock gauge is crap.

Really, you need to install an aftermarket Auto-meter Mechanical and never look back. Very easy to do great peace of mind.

(thanks to whoever I borrowed this pic from )

 

[HemiAlex]

Burping the Temperature Sender on a 2F after a Coolant Change

Here is what I did. My gauge didn’t make sense and I couldn’t drive without staring at the gauge.

 

[HemiAlex]

My FJ60 project thread...

Pics here at the bottom of my post.

 

[NMfjCruiser]

I’m sure there are more accurate ways of measuring temperature than the stock gauge.But as far as it being “crap” I don’t think so. How many millions of combined 60 miles have been wracked up with the stock gauge? Mine has over 220k and the stock gauge works just fine. Now I don’t know if it’s at 183 or 190 but I don’t really care as long as I get the general idea it’s not over heating.
When I did my cooling system rebuild I probably had an air bubble somewhere (most likely the sender itself) and the readings weren’t accurate (hot sometimes,cool other times) but it’s working fine since I the bled the system again. I vote for a bad sender or bad ground somewhere.

 

[HemiAlex]

For me, 180-190* is far too much of a sweep on the gauge.

I ended up with a 10 ohm resistor to slow the gauge down to the range where 200-215 would actually be in the red.

 

[d90rover]

Burping the Temperature Sender on a 2F after a Coolant Change

Here is what I did. My gauge didn’t make sense and I couldn’t drive without staring at the gauge.

Alex,

Thx but you're describing the exact opposite of my problem, my gauge reads too low, not too high. I was pretty careful burping the system as well, no change in symptoms before or after new stat/gaskets/housing. Barely 2-3 needle widths off cold.

 

[HemiAlex]

For me, 180-190* is far too much of a sweep on the gauge.

I ended up with a 10 ohm resistor to slow the gauge down to the range where 200-215 would actually be in the red.

 

[HemiAlex]

It’s the same problem with different symptoms. My gauge is not linear, and your gauge is too low to possibly show a problem.

Even with a new sending unit, it still comes back to the issue of the gauge being inconsistent and not a reliable source of info.

Put a small gauge on it in the car to see what’s up. I even installed my thermostat upside down and it worked in an “acceptable” range.

 

[SNLC]

I’m sure there are more accurate ways of measuring temperature than the stock gauge.But as far as it being “crap” I don’t think so. How many millions of combined 60 miles have been wracked up with the stock gauge? Mine has over 220k and the stock gauge works just fine. Now I don’t know if it’s at 183 or 190 but I don’t really care as long as I get the general idea it’s not over heating.
When I did my cooling system rebuild I probably had an air bubble somewhere (most likely the sender itself) and the readings weren’t accurate (hot sometimes,cool other times) but it’s working fine since I the bled the system again. I vote for a bad sender or bad ground somewhere.

Actually, the gauges are not accurate on all Land Cruisers. It is not until you start running a scan gauge or non-stock gauges that you realize this. On my 100, temp gauge never moved but using a scan gauge, variance of temp during a variety of driving conditions ranged nearly 40*. Again, the needle on the gauge never moved enough to notice but the san gauge I was running is no doubt accurate. 170*-215* and the needle on the stock gauge remained the same. This is just one example.

I believe Toyota designed the gauges to not move a lot in a range of temps so as to not get a bunch of worried owners at dealerships complaining.

Cheers

 

[FJ60Seth]

Mine does the same thing, at normal running temp it moves about 1/8 of the total sweep. When my water pump grenaded into the radiator, the temp gauge shot up into the red, so it does work, but more like an idiot light.

 

[d90rover]

Mine does the same thing, at normal running temp it moves about 1/8 of the total sweep. When my water pump grenaded into the radiator, the temp gauge shot up into the red, so it does work, but more like an idiot light.

Then why do so many other folks' systems work as designed, and the temp gauge starts at cold and rises to about 50% sweep at full operation temp? I'm checking the wiring and ground, then replace the sensor.

 

[FJ60Seth]

Then why do so many other folks' systems work as designed, and the temp gauge starts at cold and rises to about 50% sweep at full operation temp? I'm checking the wiring and ground, then replace the sensor.

IDK. It’s been like that for the ten years I’ve owned it.

 

[Spike Strip]

The problem lies in the Fuel Gauge and the archaic way Toyota (maybe not for the time) designed the Temp circuit. Fuel gauge is NLA, that's why most put in a BETTER and more reliable mechanical gauge.

This will explain it, if you care to read:

Temp Sending Unit?

 

[Sacto60]

great thread. My guage usually shows very low, but suddenly it's showing top/close to redline. But as I drive it bottoms out, then rises at the stoplight. I'd rather chk the sender before a new stat.