Jeep coolant temperature help

[THEFERMANATOR]

Originally Posted by tsubaki

Thanks FERM, the sensor I replaced is the one at the rear drivers side that disabled the temperature gauge when disconnected. The one at the thermostat housing initiated the electric fan and set off the check engine light when disconnected.
New radiator and no build up in the old one, replaced it anyway. The condenser does have a few flat fins and a fair amount of gravel lodged in it but I can see through a very high percentage of it to the radiator.
This animal has never lost coolant or gave any of the normal overheat indications except for the gauge.
I'm aware of the air blockage especially on the ones that have the funny looking tank. This one has the regular old overflow type.
My next thought was to replace the condenser, basically because of the elimination process order I've replaced prior. Then pull the head and replace the gasket if that don't help.
First I'm gonna do like spare suggested and see if I can determine if the gauge is close to correct.
Keep throwing this stuff this way please!

I would start by going to Chrysler and buying BOTH the coolant temp sensor(one in the t-stat housing), and the sending unit(one in the rear of the head). Eliminate those two from the equation. I cannot stress enough to not use aftermarket parts for the electrical if you don't want to deal with grief just like this. And if there is any debris to speak of in the condenser, it will run hot. Also put in a factory OEM t-stat from Chrysler while you are doign the CTS and sender. It will be a hotter t-stat, but they work much better. I've had alot of problems with aftermnarkets here lately hanging until 225-230 before they open, and then plummet down and work like they are supposed to.

[tsubaki]

Would you believe it was the MAP sensor causing the problem all along and there were no fault codes to indicate such?
I now have 3 OBDII readers and a temperature gun in the stock pile, the first two OBDII readers would not link up to the computer. I accidentally found/purchased the third reader and it confirmed the overheating.
For the meanness of it I replaced the MAP sensor and after a week of driving and a tank of gas the gauge never got over 205°.

[tsubaki]

And yes I realize this thread is over a year old.
I've been fighting this thing since August 2012!
And FERM the fan would come on at 221.9°, so you were dead on the money!

[randlemanboater]

Glad you were finally able to fix it...if you are like me, stuff like that can drive you crazy until you figure it out.

[Destroyer]

Congrats Tsubaki.. It's been a long hard fight I'm sure. Glad you came out the winner. Now it's miller time!!

[spareparts]

MAP sensor? Was it running rich or lean? it doesn't make sense to me, but whatever works

[THEFERMANATOR]

Jeeps run lean to begin with for emissions reasons. If the MAP was far enough off it can push stoic up to around 15.5-16:1 which would lean it out big time. Never heard of one doing it at idle unless for some reason it wasn't going into closed loop.