View single post by DonBurns
 Posted: 08-16-2017 07:12 pm
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Joined: 09-18-2015
Location: Fullerton, California USA
Posts: 75
Has anyone calibrated their stock water gauge to determine what temperature relates to a given position? I have been working with a possible running hot situation, and am now a little suspicious of the actual gauge. This is a fresh rebuild to a 2.2, 9.6 CR, new 3-row radiator (Aluminum), new larger oil cooler, electric fan added (on front, pushing rear), fan shroud and replaced the sender. I had the engine rebuilt by a machine shop and I'm pretty confident they cleaned the block - as near as I could determine from inspecting it before assembly anyway. So really should not run hot. I went to a 160 thermostat. The gauge goes to the center of the range quickly, then slowly climbs to just under red. It has never actually overheated.

I am suspicious of the gauge because I searched on the forums, and found the previous owner of 15800 posed in 2011 that the car ran hot. There is pretty much nothing left of the original engine after this rebuild, so that seems strange.

Today I took the sender and soldered a ground to the side, extended the lead wire and dropped the sender into a flask of boiling water with a reference thermometer and watched the gauge. I left the gauge in the car and ran the engine so the voltage would be the same. The point just below red where my car wants to run turned out to be 200F, and the center of the gauge turned out to be 160F. Is this what it should be, or is the scale shifted up? 160F seems kind of low for a target running temperature. I am in California, so ambient of about 80-90.

I have seen posts suggesting normal running temperatures of 180F. But this seems to not match my experiences with a hot radiator. Boiling temperature for 50:50 antifreeze is over 230F, and something higher than that under pressure. With a hot car just parked, I think everone has learned to not open that radiator cap for awhile, and not just a JH but a modern car with the temp gauge showing below center. If the water was at 180F, I would not expect to blister my hand (should I ever be so foolish) so I have assumed typical temperatures in the cooling system were much higher.

I believe some have replaced the Lucas gauge with modern digital gauges. What temperatures do people really run at?