Oh and the thermostat is 160*F opening thermostat. So it shouldn't really be running at 210 technically.
You need to stop thinking that the thermostat is key to what temp the engine will run at. It's not. The stat only sets the engine's minimum temp. Most 4.0s run at 200-210 with 195 degree stats (including my own; that's how it's supposed to work). If it runs at 200+ with a 195, it'll run at 200+ with a 160.
If your aux fan is on all the time, I don't understand at all how turning the AC on would affect your temps so drastically. Turning your heat on would though because doing that essentially adds your heater core to the cooling equation as a mini radiator.
Have you ever verified these temps with a more reliable instrument like an IR gun? I know you replaced the sensor/sender, but those things are not very accurate and can be faulty out of the box.
Have you thoroughly flushed (forward and backward) the system?
X2 on the temp verification. Maybe I missed something in one your posts but the suggestion was made way back and I have not seen a response to it ??? In other words you could be wasting a lot of time and money chasing a problem that does not exist.
A nation that "forgets" it's defenders, Will itself be "forgotten". Semper fi
91 XJ 4.0 5spd 5.5 on 32's, flat flares, sand camo'd. "Battle Wagon"
01 XJ 'Up Country' 3.5 on 29's former fire vehicle. Bright red. "Fire Wagon"
mschi and cbenze - I hear you loud and clear on both the function of the thermostat and gauge. So next step is going to be check the temp with IR gun and see wasup. If I have done all this and the gauge is off I'm gonna feel stupid. Nonetheless I will update you and own up to it ;-) thanks again!!!!
Meh don't feel bad I believe I told you a little earlier on I was having an issue somewhat like this and that my gauge is off... You would be suprized at how many things I changed out before I had a buddy hit it with his ir gun... Don't feel bad either the way I saw it in the end was no new part put on a car is a waste eventually you where probably gonna replace it anyways especially with cooling equipment
Infob- thanks bro. Yeah I agree a new part is a new part. Interestingly, I tried to call around to see if any one has one for rent. Nada! I have to buy one. They are not too expensive but then again I don't want to buy the cheapest one if its gonna give me false reading. So I looked at amazon and they any where from $14 to $80. So I'm contemplating on what to do. On the other hand I thought about buying a new sensor and sender. They are both new but when I went into this trouble shooting business, I replaced everything twice except for these two. So like you said, these things do come faulty outta the box. But both? I don't know it's certainly possible. However the gauge is now staring me in the face too. Arrrrgggghhh! I think I'm going with the IR gun first then do those guys if that is the case. I will keep you posted!
The ir gun would be the better investment at this point... If you keep up replacing parts you may never get it to read right if it is off and only a couple ways to test that and that's with the ir gun...
If I had the spare cash I would buy one but if your really strapped I think you where looking at the wrong place... Most little shops will do free check engine lights and tell you what code came up... If you find a shop that does that then you more than likely found a shop that would be happy to hit the tstat housing with an ir gun for free after all it takes even less time than plugging in a scan tool...
I believe after all my researching mine is reading wrong because I was cheap and purchased aftermarket cheap oem knock off sender and sensor... I have a feeling that if I purchased a true oem sender and sensor from mopar parts it would be more accurate... I'm just cheap and lazy and don't get bothered by the fact it is off by 30 degrees give or take... I rigged up a toggle switch to my e fan so it doesn't really matter...
I would call up a few of your local 4x4 shops first before asking normal shops because I found that in are expensive hobby you want to have a main shop to handle all your 4x4 needs... Just like any shopping place you want a good atmosphere with people you know and can talk to confidently... Even if I can get a part for a few bucks cheaper online I still go to my preferred local shop
Not sure if y'all as still around but I did the IR temp gun thing on the suggestion by Infob and it turns out the engine is running 25 degrees cooler at least by the IR Gun. The indash gauge would read 210 and thermostat housing would read 185.5 or so with the IR gun.
I know I have coolant temp "monitoring" points; one is upfront towards the radiator whereas the other one is at the back of the engine by the drivers side. I think I am going to replace the one at the back of the engine which, I suspect, is the temp sensor.