3.8 running hot in colder weather, battery related?

[NLJeep]

Hi all,
Been offline for a while, and jeep was running fine for a long time.
However recently a issue has been developing... Which I can't place..

The symptoms are :
-Sometimes (with engine still warm from driving longer distances) the car won't start, just a click then nothing. I notice the battery. Voltage drop below 12v and jumping up again directly after. When I wait a couple of minutes, the car will start just fine.
-Sometimes, think kits quite random, the engine seems to run hot (up to 112'c), fan kicks in etc. The strange thing is that it happens on cool days (24'c) and without me pushing it at all (80 on freeway, 50 in town). It seems to get warmer on those cooler days than in the warm hot Perth summer days
- no Fault codes ( according the scangauge)
- battery is being charged between 13.8-14.4 volts
- it's regular serviced, and had a radiator flush couple of months ago.

Now, I suspect the battery is on it's way out (original jeep battery, 2/3 yr old), and has little acid marks on top. So will replace that anyway.

But any idea what and why the engine could run hotter? Is a weak battery making the computer think the engine runs warmer? Do these things have a thermostat that gets old? Any ideas to point me to things to check?

I rather have an idea, before I drop at dealer (stealer) to lose a lot of $$

Cheers.

[BLUE09]

If you voltage is sipping below 12v time for a new battery.

I picked up a Optima Yellowtop (D34) for $254 including postage and that is going to be a beast of a battery (also warranted for 3 years)

[NLJeep]

Originally Posted by BLUE09

If you voltage is sipping below 12v time for a new battery.

I picked up a Optima Yellowtop (D34) for $254 including postage and that is going to be a beast of a battery (also warranted for 3 years)

Yup, will change battery anyway.
Note, voltage only drops below 12v if the car doesn't want to start, after the "click", guess it's the starter engine that then pulls all the power from the battery. Normally if it starts you won't even see the voltage drop.

Any idea's on the heating issues? that's actually what worries me most!

[yetiboy01]

If its an auto could be the transmission neutral start switch (gives the same symptoms as a flat battery) next time it does it, push the tranny lever forward against the stops & try starting it, if that works it means the neutral start switch is buggered & the tranny will have to come out to replace it as it is an internal component

[BLUE09]

Do you have a clam meter to see how many AMPS the battery is pulling from the alternator?

The heat is something that I have found quite weird on the JK, the thermo fan seems to kick in whenever it likes, is it moving beyond the middle of the gauge?

[BLUE09]

Originally Posted by yetiboy01

If its an auto could be the transmission neutral start switch (gives the same symptoms as a flat battery) next time it does it, push the tranny lever forward against the stops & try starting it, if that works it means the neutral start switch is buggered & the tranny will have to come out to replace it as it is an internal component

if the neutral start switch is disengaged the car does not even click.
I had the click of death the other day and it was one of the first things I checked.

[yetiboy01]

Originally Posted by BLUE09

if the neutral start switch is disengaged the car does not even click.
I had the click of death the other day and it was one of the first things I checked.

I didnt mean disengaged, I meant faulty, 2 different things, with a faulty neutral start switch the the solenoids will click & the lights & power drops off when the key is turned, I can show you if you like, same symptoms as a flat battery, catches a lot of people out,