not sure if this is something I should be too concerned about or not but thought I would ask. When the disco is sitting running for about 20 - 30 minutes (after it has been driving for at least an hour) I notice my temp gauge tends to go up, now when I say up I mean it goes about 3/4 of the way up and it is still in the "normal" bracket. Another factor that I should add is on the 2 separate occasions that I have noticed this, I was sitting with the A/C on max and the outside air temp was probably around 105 - 110 (I do live in a desert!). Once I start driving again the gauge would be at its normal spot before I have even gone a mile (the normal spot is when the needle covers the bottom of the little thermometer symbol)
anyone think this is normal temp fluctuation for a non moving truck with the A/C on high in the AZ heat? or what should be checked? The electric fan works as it should.
I do need an oil change, could worn out oil have anything to do with it?

 

Sounds normal for the climate conditions. I would recommend an additive like Water Wetter and Purple Ice to help the cooling system deal with the heat. I used Purple Ice in my Dodge while I was in Phoenix and never had a problem with the heat. The extra load of the max AC on the engine while idling will create more heat.

 

thats what I was thinking too, I would imagine the oil needing to be replaced wouldn't help either right? oil is supposed to lubricate the moving parts and as it breaks down it does that less so in my mind the weaker the oil gets the more friction inside the engine and the higher the overall temp. does that sound correct to anyone? I guess you would just notice it more with an aluminum block then most engines as the heat would transfer more easily.

I will get the oil changed and a coolant additive put in this weekend.

 

Might also make sure there isn't any debris between your radiator and condenser. I popped mine out and there was a ton of leaves and crap between the 2 restricting flow. I took the radiator to have it backflushed while it was off. Now my temp doesn't rise any.

The factory gauge sucks, your temp fluctuations are actually a lot more than the gauge reads. It is not good to have spikes.

Oh, and Purple Ice is a great product. good for yoru water pump too...

 

A oil change and a heavier motor oil like 15w-40 will help alot, and like everyone else said that is to be expected for your climate.
I would not use a additive though.
If you clean your engine and rinse all the dust and dirt off of it it will run cooler, the dirt acts like a blanket.

 

thanks guys I will do all of these things.

 

For most things I would agree with Spike about not using additives but tests and personal experience have shown that Purple Ice or Water Wetter really be improve the cooling ability of your system.

 

Chris, I used to live in Arizona, and what you are describing is no normal and is pushing your engines upper limits.
You need to verify your electric fans are workin, the viscus hub is not failing, your radiator is not plugged and your t/stat should probably be replaced.

 

I made the mistake letting my car sit for a good 15 minutes with the a/c on after work last summer so I could cool the car down. Just before I hopped on the freeway I noticed my car started overheating and before I knew it I was replacing my head gasket...Now Im petrified to even use my a/c

 

The A/C had nothing to do with it nor did the idling.
I was just time for new headgaskets, that is the #1 most common repair on a DII.