73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Stewart G Griffin on July 05, 2014, 07:19:51 pm
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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.
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P.S.
The sender for the gauge is in the intake manifold near the water neck. i don't know if this helps.
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Did you crack the sender to make sure fluid comes out? Could be an air pocket maybe.
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air pocket would be steam and it should still read it. a pinched line? never seen a mechanical one fail
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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?
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I've never seen a mechanical temp gauge. How does it attach to the motor?
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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.
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Okay. So it heats up and builds pressure which in turn moves the gauge. Interesting. So, I would think a leak then.
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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.
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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)
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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°+
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Yeah, mine doesn't read anything. i am busy with work etc. but will check it out asap.
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The line is not clear, so i can't check for fluid leaks. No damage to the line either. Any other suggestions?
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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.
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ok
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i put the probe in boiling water and nothing. Also, when removed from the intake it was definitely touching water. i think time for a new gauge. These were the cheap Chinese ones from summit:
http://www.summitracing.com/parts/sum-g2924/overview/
My theory is they worked fine all along until last month i ran the motor to about 260 degrees---was caught in a traffic jam and i still have not put a fan on; See my other post entitled "waterpump pulley to fan bolts"
http://forum.73-87chevytrucks.com/smforum/index.php?topic=12865.0
My theory is the gauge couldn't handle the high temperatures. Well, it worked great while it lasted. i got it and the oil pressure gauge for $14 back in summer 2006 at Summit.
Has anyone used the Autogage Ultra-nites?
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This dual gauge set, oil press+water temp, is now $19.95 at summit. So, you figure $9.50 per gauge. What do you expect? You get what you pay for.
Forget about Ultra-nites---i just found out there's no way to hook up lighting to it.
i'm going to go with the cyberdyne unit that has been sitting on my shelf for a while.