[DeTomaso] water temp sender

[tmshinro at aol.com]

 After reading this thread, I'd thought I'd chime in with some trivia and a question.

When I got my '73 euro GTS 23 years ago to restore, I was having over heating problems.   I bought a temp sensor at the local autoparts store (don't know what kind) and installed it in the block, leaving the original sender in the pressure tank (because I couldn't get it out).  After running a wire from the new sender to the Veglia gauge (reads in centigrade) I wanted to know how accurate the gauge was.  I bought an American temp gauge at the auto store and wired it to the temp sender in the block and noted the temperature reading after the engine was hot enough to turn on the fans (original).   I don't recall what the temp reading was.   I then installed the Veglia gauge and noted the temp reading when the fans came on.   After doing the conversion, I determined the Veglia gauge was reading the same temperature as the American gauge.  I even went so far as to buy another euro temp gauge, just in case mine was bad, and found it read the same as my original.   [In case you're wondering, I bought the euro gauge and a lot of other used parts from a guy in Chicago (Mike Staski?) who advertised in Hemmings.   Turns out he had several Panteras he parted out from his home.   He was a real nice guy and easy to deal with.   He was really trying to talk me into buying the whole set of euro gauges instead of just the temp gauge because there wasn't much demand - $50 total if I recall, but I didn't do it.  I remember he used to list the parts on IBM punch cards when he shipped them to me.]

Anyway, I convinced myself that the euro gauge was accurate and the fans came on just before the needle hit the line between 70 degrees and 110 degrees (which I assume is 90 degrees) which matched the temp fan switch temp in the radiator.  I also installed a Hall radiator shortly afterwards because the factory one leaked.  I never saw an indicated reading over 100 degrees.   I never had a boil over so I figured everything was OK.   All this happened long before I found this forum and started reading accounts of other owners' problems/solutions.

Fast forward to last summer after two decades of fun-filled motoring w/o temp concerns.   I had to fix a leak in the Hall radiator and after re-filling the coolant and purging air I now find that occasionally my temp gage will go full scale over 100 degrees and then after several minutes (sometimes more) will suddenly drop like a rock to 80 - 85.  Any thoughts on what could make this happen?   Air bubbles at the sender or electrical gremlins at the gauge?  I don't see any drop in coolant (filled to the cap seal rim on the tank) and no bubbles at the radiator bleed screw so I figured there wasn't any air in the system.  I have not had any boil overs.  

By the way, I've also been meaning to ask if entrapped air purges itself via the overflow tank.

Tom
#5186