Quote:
Originally Posted by Big hammer
Yep heating metals makes them expand………. Then when it cools it shrinks a teeny tiny bit………. Just what body men do with sheet metal, heat shrinking :-)
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The heat/cool process if about getting enough expansion/contraction to break the bond of the corrosion. It's not like putting together pressed assemblies where a part goes in the freezer and you heat the other part so they can be easily assembled.
The problem with this type assembly is you have a hollow soft brass tube with a hex cut on it. It's a tapered thread so it seals by being firmly jammed into the other threads. A open end wrench just deforms the tube and lets the wrench round off the hex. When it gets bad enough vise grips are all that works. He could pull the neck and unscrew the main fitting without destroying the temp gauge tube.
But since he's trying to "replace" the gauge cut it and take it off at the water neck. The new gauges come with an assortment of adapters. Put the new one in with teflon tape and tubing wrenches. The next owner will thank you.