Mechanical Temp Gauge Accuracy?

[Ky Hillbilly]

Looking for some comments on the accuracy of the autometer mechanical temperature gauges. I have a 76 40 with a 2F engine. Did a restore project and had the engine rebuilt, new bearings, rings head rebuilt etc. Anyway got it running and put a few miles on it maybe, 80 and waterpump went out. Installed new pump from Advance auto. Water temp didn't get over 200 before new pump but weather was cool at the time. Now I'm getting readings of 240 after driving it at 60 mph for around 20 mins or so. Borrowed a infared temp gun from work and I'm getting like 170 temps at T-stat housing and radiator inlet with around 150 at the bottom outlet. I read some comments on the autometer sight about the temperature reading was a core temperature of the actual antifreeze temp. Seems like a big difference to me, I'm thinking about pulling the temperature bulb and putting it in some water with a thermometer and check the difference. Has anyone else experienced this?

Thanks

 

[JTeeg]

The gauge is pretty simple with an acuuracy of +/- 5 degrees. I had problems with mine reading high on my LS1 engine but once I got all the air out the mechanical gauge reading agreed with the LS1 factory sensor.

 

[JohnnyC]

What's the temperature at the sender that's on the head?

May have air in the system still? How many miles on it since replacing he water pump?

 

[Ky Hillbilly]

Temp at the head is around 170, miles are around 50 maybe with the new waterpump. Yesterday I back it down a bank and put a big funnel in the radiator and poured a little water in, and started it, the level rose in the funnel and got a little air out, not a lot. Did find the overflow cap was plugged, blew it clear with some air and the reservoir was empty this afternoon when I checked it. Filled it back to the cold level mark and drove it got it around 240 was max temp then checked it with the infared gun.

 

[Steamer]

The only way you'll know for sure is to pull the bulb and check it with several thermometers. If you can boil some water to check it that would be good too. Here's a link for boiling temp corrections for altitude or barometer. http://www.hi-tm.com/Documents/Calib-boil.html#tables

 

[oestlarsen]

I struggled with this on my FJ80 and my FJ40.

The 80 has Autometer gauge (digital) with sensor on upper rad hose. Reads 200 when infrared says 180ish on the thermostat housing.

The 40 has a mechanical gauge which barely cracks 150. I doubt my 40 runs that cool so will do further infrared tests on the areas you pointed out.

Autometer says make sure gauges have excellent ground.

Both the oem gauges read right in middle (no surprise

 

[FF LC FREAK]

If you tweek/overly bend the wire between the sender and the gauge, you can get really erratic readings. BTDT. There is no way to fix it other than buying a new gauge. You might want to take a look at the wire and see what kind of condition it is in. Just something to check.

 

[Ky Hillbilly]

Cable to head is good, I'm thinking it is getting that hot, the dash gauge is showing hot too. I'm thinking I'll replace the thermostat and see if that helps.