I don't really have an issue, but am hoping to gain a little insight and maybe a little corrective action can be applied or this may be totally normal. Recently I changed my coolant reservoir/ degas tank on my 02 4.7 liter. What started it was a post by a member here who was having an issue similar to mine with coolant constantly leaking out of the overflow tube, and he tried an OEM cap and it cleared that up. My overflow always leaked since I bought the truck, and after a plug change the neck on the degas tank began in as well, I assume from me leaning my fat **** on it while changing plugs. Because of these 2 leaks I have had to add about 1/4 gallon of antifreeze a month. I was out around the time he posted about the rad cap so I went to the dealer and bought the cap and a gallon of antifreeze. The cap cleared up the overflow problem but the neck still leaked. After I tried a few home grown repairs that failed I just bought a new tank. This cleared up the neck leaking. That was a week ago and not an ounce of coolant lost after bleeding a few times with cap off and bleed screw opened.

My question has to do with my temp needle moving. I have owned this truck for 2 years and it has done this since I've owned it but became curious after searching about the degas bottle and read somewhere that the needle is supposed to stationary. What I mean by moving is that if I start the truck up and don't drive, just let it idle, the needle will go all the way up to a tick below the halfway point and stay there all day at idle. If I drive in the city or speeds below 60 it will stay there until it reaches idle again (stoplight, etc) then it will sit right on the halfway mark. On the highway (speeds 60 and above) it will sit on halfway for a while, then it will go back down to a tick below for a while and so on and so forth. If I drive either city or highway and just put in park and let idle it will sit halfway. The only time I have ever seen it deviate from this is when my old radiator began plugging up to the point that one of the seals busted out, then it would go a few ticks north of halfway, and finally when my old radiators seal blew it went halfway between half and the black mark before the hot mark. So I never did overheat it. It also went a tick past half once in 90• Weather with a/c on blast going up hill. Other then that it moves that bit I described and has done so for 2 years. Is this normal?

A little back story on the truck. When I bought it the radiator leaked from one of the end caps. I drove it like this for a year or so and kept adding fluid. I read about the clogging radiators and that one would be piping hot on the lower drivers side corner (where it was leaking from) and ambient temp everywhere else. I never did change it as something always came up when I had planned to along with a bunch of personal/ family stuff won't get into. Long story short it finally blew the seal while I was leaving the parking lot at work one night, never did get hot, turned heater to full and parked it in the shop. I went to the store and bought a new rad, cap and thermostat and changed it. And the temp settled into doing what it had/ has been doing. I figured this was normal until I read that it should stay just below half and not move. The radiator temp is the same as the day I put the new one in- on the drivers side it is piping hot, where there is a 20-30• Difference on the passenger side. I can't hold my hand anywhere on the drivers side, and can on the pass side and eventually the heat on the pass side will seep through where I have to move my hand, same with top/bottom hoses. The fluid remains a nice purty red color and clean, and I cannot stop the clutch fan with newspaper.

I would appreciate any ideas or input on this. As stated before I don't really view it so much as a problem rather then a curiosity. I'm sorry this is so long and hope I didn't confuse anyone.

Oh, and to address this before anyone who automatically posts/ assumes the worst with any thread where 4.7 and temp are both mentioned, I am fully aware of the HG issues prevalent with 4.7s. When I changed the rad the first time I found some emulsified junk covering the thermostat and inside the bottom hose connection of the degas tank and became convinced that my truck either had or has in the past had a HG failure. I pulled and changed the plugs only to find that they were new. With it ****ling at my brain I had the truck pressure and compression tested and both tests came back clear. No water in oil and vice versa, nor coolant out the tailpipe, and heat is great at idle (well on the passenger side- blend door issue) Also when I changed out the degas bottle last week the junk wasn't there. I can only assume a failure in the past and this junk may be what plugged my original radiator in the first place. Again sorry for the lengthy post and thanks for any thoughts.

 

Sounds like you're seeing the result of the 'stat opening and closing. I have a 180 'stat in mine. On the highway, the needle stays just above 1/4, which works out to 181-182 on my Scan Gauge. Puttering along in traffic, the needle climbs to ~1/2 (the old "normal") which is where my e-fan kicks on. The fan will pull it back down on most days. On really hot days in traffic the e-fan just holds it to 1/2ish. Once I'm back on the highway or traffic lightens, the gauge goes back to 1/4ish and the fan shuts off.

 

Thank you Mike. After I read that post about the temp needle not supposed to be moving I wondered if I was the red headed step child lol. My ignroance is going to show here, but I was under the impression that once the engine reached a certain temp the 'stat would open and remain open until the truck cooled down again?

 

It does. The stock 'stat opens at ~203, slowly I think. That is, it begins to open at 190ish and is fully open at 203. The 'stat opens and closes as needed. I wonder if the post about a needle not moving referred to the oil pressure "gauge", which is barely more than a switch (pressure "yes" or pressure "no").

 

My oil gauge moves as it should. It is not a dummy switch.

 

My old 04 4x4 4.7L quadcab did similar as yours. Most of the time it was around that mid mark on the gauge. In Summer, on long mountain freeway hills it would move a little bit up above half. With a Load (RV trailer, around 4400lbs) on the same hills in summer, it would get as high as the 3/4 mark on the gauge. The 4.7L is a bit smallish for the weight of the truck, so it works a bit harder producing more heat. The cooling system on it is probably more suited to the Jeeps and Dakotas that the engine first came out on. As such, under the extra load the cooling system can't keep it at ideal temp. My truck had the factory tow package with heavy duty cooling... but it still did that. Never overheat, never go beyond those limits. Even after a full coolant system flush/change. I just took it as normal for that setup. Long as it isn't overheating, it should be ok.