Good and Bad day
 

The good "the ole gurl" hit 400000 miles today on a trip from Lee NH to Point Pleasant NJ alas no pic Had to stop once coolant level light came on but only took 1/3 gallon Temp Guage held steady at 80
The bad ; very little heat lukewarm at best no better on defrost I know there are many different things to look at can someone put them in the proper order please

I suppose being in the in crowd would help responses

I'm having a similar problem with mine. Suspect either a monovalve not opening all the way or a clogged heater core. Haven't had time to dig in to it.

At least you hit the 400,000 mark!

When was the last time the t-stat was changed? Also check the radiator/expansion tank cap.

I guess thing happen in NC as well as Texas, huh?

the ole gurl hung steady at 80C on the trip going up maybe 5 degrees pulling the hills in conn so i dont suspect the Tstat That make sense? A good rad flush should be done though not until it gets a lil warmer though

Which car is this on? Does the climate control show any other symptoms to point to it being the problem? If it kicks the a/c on when you ask for cold air and regulates the fan speed like it should, you could just have a sticky monovalve. Monovalves are funny things. When they don't get a signal from the ccu you get full heat but somehow when they're torn you get no heat at all.

The first, and easiest thing to check is the monovalve diaphragm. Pull the four screws, remove the solenoid, pull out the diaphragm and check it carefully for any tear in the rubber.

The thermostat is not the issue.

it is my sdl and ac doesnt work anyway fan works minimal heat drivin no more on defrost then other settings little more heat parked

Since you have good operating temps, T-Stat is ruled out.

See if you can get a 10 or 16 oz plastic bottle to stay put under the hood, near that battery. Put your overflow line in the bottle and see if the car is losing coolant that way. If you are not losing coolant internally, and no mixing of oil and coolant, the cap could be getting weak.

Also, check the monovalve as suggested.