M-I-K,
Do not keep the liquid filled gauge under the hood.
Here's how I know this:
First Coast Cobra Club • View topic - Liquid filled gauges - lesson learned!
If you must, put it somewhere there's no heat.
I was lucky - the carb percolation/overflow didn't cause a fire
You may or may not have the same luck.
If you require a gauge under the hood, get a non liquid filled one. They're inexpensive and much safer to use:
http://www.summitracing.com/parts/aei-15632/overview/
'nuf said,
Tom