Strange Temp Gauge Behavior

[uzj100]

LC in question
2000 with 207k odo miles but probably closer to 218k since I have been running 33s since 100k miles

The temp gauge has really started moving around. The needle use to sit in the bottom third of the gauge no matter what. Now the needle moves from bottom third, to half to 75% and back. This has me concerned however the truck runs better than it ever has.

I have checked the fluid level and that is all good. I did the fan clutch test, all good. I am thinking thermostat.

Please chime in and let me know. Has anyone else seen this behavior? Could it be something loose? This started happening after my wheeling trip to Uwharries 2 weeks ago. I wonder if it is a fuse or loose wire?

Any insight would be greatly appreciated.

Thank you in advance.

uzj100

 

[Trunk Monkey]

The OEM temp gauge is notoriously inaccurate. The different from the bottom to the upper "normal" range is a huge actual temp area. And then when it does peg "hot", you're already boiling. Do you have a Scangauge or other OBD device to see what your actual coolant temps are?

 

[mgilvan]

my gauge seats right at the half point

 

[uzj100]

When i run the heat, the needle moves down to about 40%.

 

[2001LC]

Sound like thermostat (running cool). Check your wires if properly connect and not corroded but engine running cool would indicates a weak thermostat (weak from age), going to hot would indicate sticking thermostat. Your gauge if working properly should be centered at normal operating temp (during normal driving condition).

You may also want to check the weep hole for coolant leak indicating water pump going, but it doesn’t sound like that’s and issue.

 

[mgilvan]

thanx 2001LC

 

[adrenalinefjz80]

If your mpg took a drop, the tstat could explain if it failed open and runs cool.

 

[midwest2]

LC in question
2000 with 207k odo miles but probably closer to 218k since I have been running 33s since 100k miles

The temp gauge has really started moving around. The needle use to sit in the bottom third of the gauge no matter what. Now the needle moves from bottom third, to half to 75% and back. This has me concerned however the truck runs better than it ever has.

I have checked the fluid level and that is all good. I did the fan clutch test, all good. I am thinking thermostat.

Please chime in and let me know. Has anyone else seen this behavior? Could it be something loose? This started happening after my wheeling trip to Uwharries 2 weeks ago. I wonder if it is a fuse or loose wire?

Any insight would be greatly appreciated.

Thank you in advance.

uzj100

I had these exact symptoms on my 00 LX 130K miles last year. I really started to notice it when I was 1500 miles from home so I watched the gauge like a hawk the whole way home. I changed the thermostat and fan clutch at the same time and that fixed it. I believe it was the thermostat but thought I'd throw on a fan clutch while I was right there working. Both jobs are very easy.

 

[uzj100]

Thank you for all the assistance. 17 bucks from Toyota and a 4 dollar gasket. Time to get dirty.

 

[uzj100]

The thermostat fixed the issue. Back to the same as before, temp gauge needle sits at 35%, no matter what.

30 minutes to change out. Pretty straight forward. The coolant makes a mess but besides that, very easy to do.

Thanks again for all the assistance.

 

[2001LC]

The thermostat fixed the issue. Back to the same as before, temp gauge needle sits at 35%, no matter what.

30 minutes to change out. Pretty straight forward. The coolant makes a mess but besides that, very easy to do.

Thanks again for all the assistance.

Regular flushing with Toyota red & distilled water is a great Idea, I just did mine this weekend.

 

[uzj100]

True, This was probably the original thermostat.

 

[2001LC]

True, This was probably the original thermostat.

That's a testament to Toyota thermostats, and good maintenance. But your temp gauge is odd, should center. You may want to check your sending unit

 

[uzj100]

It has been sitting at this current position since I purchased it with 100k miles. I will post a picture.

 

[uzj100]

Gauge

 

[2001LC]

View attachment 812398


Gauge

That looks good to me, just below center. My gauge on a 100 deg day with air on full, will rise just above center. Apparently the actual temp swing is much greater but within acceptable range. I guess Toyota didn't want consumers alarmed by the wider swing.