89 Towncar overheats

When it gets cold (about 40 Fahrenheit or less) and I drive the car after it hasn't been driven for a few hours, the temp gauge goes way up and there's no heat. But after a little while I can rev the engine hard and the temp drops and the heat starts blowing warm. The radiator is full with pretty much 100% antifreeze. Ideas?

When it gets cold (about 40 Fahrenheit or less) and I drive the car after it hasn't been driven for a few hours, the temp gauge goes way up and there's no heat. But after a little while I can rev the engine hard and the temp drops and the heat starts blowing warm. The radiator is full with pretty much 100% antifreeze. Ideas?

Replace the Thermostat.

Yup, sticking t-stat.

A shortage of coolant, or air pockets could make the thermostat look bad too.
Try adding a boost of prestone treatment for freezing, boil over, and rust protection.

How many years sense the last coolant flush + change?

See neglected coolant service -
www.automotiveforums.com/vbulletin/showthread.php?t=155214 (http://www.automotiveforums.com/vbulletin/showthread.php?t=155214)

OMG Coolant system Corrosion with pics
www.automotiveforums.com/vbulletin/showthread.php?t=1083343 (http://www.automotiveforums.com/vbulletin/showthread.php?t=1083343)
100% coolant protection, I wouldn't think corrosion would be a factor.

Caution - You really don't want a freeze plug, or the heater tube going bad, the coolant protection shouldn't be no more than 70%.

Action -
1) If 100% Coolant, drain 30% of the coolant.
2) Add a Peak/Prestone T-flush kit, so you can use a garden hose + water pressure to force out any air pockets with engine idle + the HVAC on heat high max.
3) Check coolant level and test coolant when cold.
4) Test coolant fans