Green temp light stays on (after flush & thermostat replacement) Solved!

[7milesout]

The Mirage has a resistive heater in the HVAC plumbing somewhere. It switches on at low coolant temps to provide a little bit of warm air before the coolant can deliver it. So blowing max "heat" when the coolant is cold will load up the alternator and cause you to use more fuel!

Metro - You and I (and maybe others on here) have a very similar ridiculous brains. I'm in agreement with your statement. And find it ridiculous, but interesting, because my brain is different from others.

As for my statement about pulling heat off this way might not extend the amount of time the green light is on ... I was WRONG. I did this a couple times now, just as an experiment. If I turn the key to ON, turn the fan speed on max, then beep the temp thing up 400 times to get to 89°F, or whatever the hottest temp setting is, then crank and drive, it will go MUCH FARTHER before that green light goes out.

I don't plan to keep doing that. I just wanted to know, to experiment. So in the future, when I'm doing some heavy haul towing and pulling mountainous grades in the heat of the summer with the Blueberry, I'll drop windows and run the heater on max temp / max fan for supplemental engine cooling!

I actually have done that twice (not in the Mirage). One time I was with the family in DEATH VALLEY, on vacation. We were in our own personal vehicle. A 2006 Honda Odyssey Touring, and it had about 150,000 miles on it at that time. Quite a good vehicle. Awesome for a family of 5. It was in the hottest part of summer, and when we started to pull long steep grades, I told the family, hey let's be warm for the next 10 minutes or so and do this. I was concerned about becoming stranded on the side of the road, in our personal vehicle. It's not like it was new. I wanted to take no chances, to be able to haul the family back across the country to Atlanta. So we did it. The boys thought it was fun. The wife understood and made no complaints. But there we were, pulling this long steep grade in Death Valley. I'd clicked the O/D off, put down all windows, run the heat on max, and was running a very healthy rpm for the 3.5L. Meaning, I was probably pulling at about 2,400 rpm, where the engine was very happy and very torquey. No lugging. And was following speed suggestions. Here I am taking all these precautions up a long steep grade, and a black guy in an old crusty 80's Caprice Classic comes hauling past us, passing in a 2-Lane on solid double lines, windows up (so A/C was on), like he didn't have any idea where he was. I only mention he was black just because it seemed out of place. Because he was young, by himself, and in a vehicle that looked like if any vehicle was going to have trouble in Death Valley it would be that one. And all I ever saw besides him was families. I had zero issue with him passing me where he did. Even though it was a no passing zone, it was evident it was clear, and even though he was going fast, he did it safely, and he seemed more than adequate to be able to handle his business. I thought I might see him again, prior to the crest, on the side of the road. But I didn't, he made it just fine. Funny the things one remembers. I was glad he made it. For all I know, he might have maintenanced his car to the peak of performance just for that. He did look like he was enjoying himself, and I was glad for that. That was one hot day. Got pictures of my sons at the visitor center acting like they were cold standing by the big temp gauge that was reading 129°F or 130°F.

One other time I did this was in my blue truck. I was towing WAY heavy, was in the mid-west somewhere. And it was just roasting hot. I saw my coolant temp gauge climb a bit higher than normal. So again, I dropped the windows, fan full speed, max hot, and it pulled the temp gauge back down to where it normally runs. Ran that way for hours during that hot day.

[Lewacool1]

I would argue that if the seal didn't seat properly, you'd be leaking coolant out the thermostat housing due to that being the only means of sealing the thermostat and pipe to the engine block. I am having this same issue changed out thermostat and gasket but I can't see to figure out why my engine won't ever warm up. Coolant temp sensor is good, new thermostat, heater core. When car is not moving it will slowly get to operating temp but the moment I take it down the road it goes down to 130-135. It is a 2015. Do I need to do a grille block?

[klroger]

When car is not moving it will slowly get to operating temp but the moment I take it down the road it goes down to 130-135. It is a 2015. Do I need to do a grille block?

Nope, not a grille block. Take your new T-stat out & test it in a pot of water. Is it an aftermarket T-stat??? Test it to see if your new T-stat is working as it should. Some of the aftermarket stuff is kinda "sketchy" ...

[foama]

Sometimes a thermostat will fail by not closing all the way. In winter it then takes ages for the engine to warm up if it ever reaches temperature. In summer that becomes less noticeable.

There seem to be quite a few in this forum that have replaced the thermostat and still have problems. Read from the very first post on and you will see.

The thermostat has a rubber gasket around it. See pictures in previous posts. The gasket sits in a slightly recessed seat, and may not be seated properly or the gasket not seated right. It can be difficult to really get a good view of what you are doing, and then things get messed up easily. If you do want to take it apart again to check, have a very good close look. A pocket mirror may help. Also take care to not overtighten the two bolts holding the assy together.