What would cause a temp gauge to suddenly stop working?

[Stewart G Griffin]

Do you have any ideas on why a temp gauge would stop working suddenly?

It's a mechanical gauge  and when i first noticed the gauge was not registering it made me wonder if i had enough water in the system, so i parked it and yes i was real low.   i added some with the engine still running ( i always carry a few jugs of water in back) to bring the radiator back up.  Since then the temp gauge doesn't work.

The engine did not overheat as far as i know---it runs fine.   It turns out one of the heater hoses was leaking and this caused the water level to go way down.  But this has been fixed.

[Stewart G Griffin]

P.S.
The sender for the gauge is in the intake manifold near the water neck.  i don't know if this helps.

[jaredts]

Did you crack the sender to make sure fluid comes out?  Could be an air pocket maybe.

[Irish_Alley]

air pocket would be steam and it should still read it. a pinched line? never seen a mechanical one fail

[FlatBlack77]

check the entire length of the line and check for any damage. depending how you have it routed maybe it got against the exhaust manifold and melted?

[BADAZ chevy guy]

I've never seen a mechanical temp gauge. How does it attach to the motor?

[bd]

I've never seen a mechanical temp gauge. How does it attach to the motor?

They use a one-piece capillary tube filled with fluid that's permanently attached to both the gauge and a thermal bulb that threads into the water jacket.  Think of an old fashioned mercury thermometer.

[BADAZ chevy guy]

Okay. So it heats up and builds pressure which in turn moves the gauge. Interesting. So, I would think a leak then.

[bd]

Possibly; or the sensor isn't immersed in liquid.  Heat transfer between liquid coolant and the sensor is far better than heat transfer between a hot gas (such as steam) and the sensor.

[FlatBlack77]

if the line checks out alright you can move the probe to the side of the block and see if it makes a difference(doubt it will)

[Irish_Alley]

These things read even if they are just hanging in the engine bay. May not be accurate but they will read something. Buddy got a truck and I forget why but it had two temp gauges and was hanging off the booster and it would read 100°+

[Stewart G Griffin]

Yeah, mine doesn't read anything.  i am busy with work etc. but will check it out asap.

[Stewart G Griffin]

The line is not clear, so i can't check for fluid leaks.  No damage to the line either.   Any other suggestions?

[bd]

Remove the temperature gauge bulb from the water passage and immerse it in near boiling water with a thermometer in it, so you know the water temperature.  If the dash gauge doesn't read within ~3%, replace the gauge.

[Stewart G Griffin]

ok