It has been plenty cold lately, make no mistake. (It is 12F right now according to weather.com). The heat in my truck used to be STELLAR. It always took a little while to warm up from cold, but once I drove it about 10 miles or so I could only turn the temp 'dial' for the heater to about 50% or 60% in the cold:hot ratio. Anything else would cook me out, year after year through all these winters, no matter how cold it got.
I noticed last year and especially this year, I've got it on 100% all the time, and while I can still make the cab comfortable, there's a definite reduction in the level of heat coming out. Some quick observations:
1) Coolant level is correct.2) Coolant is nice and green. It has been changed regularly and has never been rusty.
3) Heater valve (on the heater hose) seems to be working through its proper range when I turn the heat dial.4) Heater fan works as it always has on settings 1 3 and 4 (2 has been 'burnt out' for years)
5) The temp gauge in the cab acts as it always has- rises and falls to the same spots as the thermostat opens and closes. This is notorious and normal on 2.5L Rangers.5) No engine miss, frothy oil, white smoke, external leaks or anything to indicate coolant is compromising a gasket or (perish the thought) water jacket.
The only thing that is wildly different is that I put a new thermostat in it last spring. It was OEM spec (IOW identical opening temp), and I can't imagine the 5 or 10 degree differences that thermostats have would make this much difference in heater performance anyways. Also, it was doing this for the year prior the thermostat change.
So what gives? I've had older cars that I've gotten second hand where the heat doesn't work so great, but most of those had rusty coolant (and likely a clogged heater core). Is this just something cars do when they get older? I can't imagine so.
Thanks. Stay warm.