What gives: Too cool in winter and too warm in summer?
filed in 1966 Mustang
Question: Maybe it’s an unreasonable expectation. Having a 180 degree thermostat and the car running at or near 180 degrees…
It’s a 1966 Mustang with a slightly warmed-over 289 (Edelbrock Performed cam, intake and 600 carb. Shortie headers).
I have the so called “desert radiator” with an overflow can. A 13 LB. pressure cap. A BlackMagic electric fan with adjustable thermostat (2800 cfm). A FlowKooler water pump. A 180 degree Robert Shaw thermostat. And a separate transmission cooler.
What I don’t have is a temp gauge with temperature degree markings. But half-deflection can be assumed as normal. Or about 180-195 degrees.
So, given all that. Why during the summer does the temperature go to nearly two-thirds deflection (forget using the AC on those really hot days because it’ll go over the top). And during the winter only one-third deflection (not enough to really get the heater going)?
I’m in central Texas. Summer days at 100 degrees, and winter in the 30-40’s.
During the summer, it stays cooler as long as I am moving at a reasonable speed. During the winter it gets warm enough as long as it’s not too cold outside. Like not below 50.
The question then: Shouldn’t the thermostat and cooling fan be able to maintain a more constant temperature?
Answer: Well,first, I would add a REAL temp guage so I KNEW what was happening. 2, I would make sure my spark advance was working correctly. Too lean and it will run hot also.
There is a fluid you can add that will drop the coolant temp 20-40 degrees in the summer. Change thermostat to a hotter on in the winter! I don’t like the electric fan and is that a 12v water pump? Neither is great for summer cooling and if it is probably doesn’t flow enough water for the thermostat to work in winter. Slow coolant heats up so much that it always keeps the thermostat open and then completely cools in the rad, re-entering the engine as chilled coolant, keeping most of the block far too cool. Just a guess.
Either of your guage deflection readings may be right, I can’t be sure from here so I tend to think one or the other extreme is the problem.
Hmmm, perhaps a dozen reasons why this is happening (it shouldn’t!). You problem could be a combination of several of these items. I’ll rhyme of some possibilities to check:
Slow coolant flow for any reason. Cooling system deposits, try a good commercial truck rad flush. Minor head gasket leak, have competant shop check for exhaust in rad. Thermostat installed backwards. Collapsing lower rad hose, has the spring rusted out inside it? No fan shroud, get one. Heater core water valve not fully opening. Head or head gasket water port mismatch if these have been changed. Over cooling rad with high coolant flow, cover portion of rad in winter. (I have this problem with my diesels in winter up here).
Want to give your own answer? Want to comment?