Hi All,
Since I have put my 66 Dart back together it has always ran warm at highway speeds (65mph+) and idling in traffic. Never gets much over 210 degrees but thats a lot warmer than I like.
Today I took it on a small pleasure/business trip run of about 100 miles round trip to Louisville KY. It ran its usual warm self on the way there and I was about to pull over and let it cool down because the temp gauge was getting out of the safe zone but then......within a matter of less than a minute the temp gauge dropped to the halfway point! I did then pull over to check everything out under the hood and (as far as I could tell) everything was OK. The rest of the trip the temp gauge stayed at the halfway mark (180 degrees on my mechanical gauge).
I don't understand why it would suddenly start running cooler. I'm glad that it did-but I just can't comprehend why.
When I got the Dart the head was removed from the block and had been given a valve job and cleaned up. upon reassembly I flushed the cooling system, replaced the water pump, new 180 degree thermostat and gasket, radiator cleaned and flow tested at local radiator shop, proper mix of antifreeze and water, timing is within specs. The 225 has been bored .040 over at sometime in its life, it runs well and does not use oil as I have put about 3000 miles on it since I put it back together.
Temperature today was in the mid 80's.
Anyone have any ideas please post!
Thanks
Todd

It's just a guess but maybe a thermostat that was a little sticky. Even new parts can sometimes be bad. Of course that wouldn't explain why the car ran hot before. Where do you have the sender mounted? The sender will read colder if it isn't actually in contact with coolant. The only place you can mount a mech sender that might not always hit coolant with a safe level is on the rad tank of the late 70's rads.

Meaby the sender unit is failing, also the thermostat could be failing.

_________________
Mopar Muscle is well defend by Slant Six!

Valiant Duster 1971