Originally Posted by lithium1330
For folks familiar with overheating issues... I'm hoping to get some insight/help.
1) whether i'm hitting radiator capacity & need an uprate radiator, and 2) whether 3mos old fan clutch is dying...
I'm also running Ultra Gauge (UG)...
It was un-normally hot just south of SF this weekend, with outside temperature around 105 - 110F. Yesterday, cruising at 75 - 80mph, no AC, my engine temp (via UG) was sticking to 206F, with the intake temp around 135F and ambient temp at 104. Before that, I was in bumper to bumper traffic for about 10min, and the temp when up to around 216 - i turned on the heater on just as precaution.
Today, ambient temp was around 98F. I was doing some city driving and UG showed 186 - 190F while moving at 25 - 30mph. I got the IR gun out at home, the top rad hose was showing 190, the bottom hose fluctuated between 145 - 180F. I could hear the fan noise fluctuate as well. I put a piece of paper in front of rad and it was sticking... I could feel hot air at back side of the radiator. And after about 15min of idling in the driveway (still around 95F, the UG showing temp creeped up to 212F, hood opened.. I've gathered, these trucks will idle all day and stay below 200F.
I feel your pain. Chasing engine temps can be frustrating. At least you're already ahead of the inaccurate stock gauge running the UG. A few things though,
1. If your truck has the 4.6, I've read on other threads that those engines tend to run hotter than the 3.9's and 4.0's. 210F would not be unheard of. If you do have that engine, did you use to run temps under 200F normally and did you notice that recently it's running higher? Or has it always run above 200F in your experience with the truck?
2. When you left it in the driveway for 15 minutes at idle, was your ac running? Mine would go up to that too under the same conditions I believe.
3. How many miles does your engine have on it? If you had to replace your fan clutch 3 months ago, I imagine it was because your original one probably free spun constantly. If it had gone bad, there's a fair chance that your water pump may be on the way out too and not giving you proper flow. It's a fairly cheap and easy part to replace as others have said. Even though you may feel air being pulled through the radiator, it is possible that your fan clutch may still not be pulling enough
air and you got a unit with a short life span.
4. The UG is really your best bet to figure out what your water temp is actually doing. I did the whole IR gun thing and really all it's good for is finding a very rough estimate of temps. The best thing it's used for is finding local differences of temperatures / looking for hot and cold spots. The OBDII grabs the temperature from the larger of the two temp senders (it's the fatter one with two wires instead of one coming out of it). It sends the temp straight to the ECU. Although I wouldn't say they necessarily are known to crap out often, depending on the age and mileage of your engine it wouldn't hurt to replace it so you can say that your OBDII temp is a lot more accurate and rule out a temp misread there too. A genuine run will run around $90.
Bottom line, if you just have a plain old 4.0 in your truck, your temps are high under the conditions you describe. Like the other guys said, start with the cheap stuff first like water pump and a new clutch. Also if you take it off road, take a look and see if your radiator is just jammed up with dried mud.