Question on a few things.

I changed my antifreeze some 15-20k ago, in the process I had the big air bubble, so I topped it off with what I had in the truck, straight antifreeze, the type the truck calls for.

The water pump sounds fine, no leak no noise. The thermostat is working, gets warm 200 then drops off. What I'm finding is that it is running at 200 or a tad over most all the time at 70 mph or more or in traffic.
In time past it would never run 200 without towing or on hills.
It would stay in the 180-190 on the gauge ( dash )

Could it be the mix if the anti freeze, to much? I hear that some talk is pure water cools and flows better and racers use that....

I have a new thermostat to change and plan to do that, but it looks on the gauge to be fine, as far as open and shut, maybe not just open enough?

In the past on all older trucks and cars, if a pump fails it leaks, makes noise,
and if the thermostat fails, it sticks shut or open, the truck will never get warm or over heats, not just running warmer then normal maybe 10-20 deg.

BTW the fan is working and I can feel the pull on it and the noise from it from time to time and when you run the air.
Belt was new 20k miles back.

123k on the truck now


What you think?

 

The higher the concentration of coolant, the less effecient it is in transfering heat. If plain water is rated as 100% efficient, a 50/50 mix is about 90%; 60/40 is 85%, etc., etc., etc.

 

Good info I thought I remember that, I think I may be a little on the heavy side for the antifreeze.
I will refill with water when I do the thermostat.

 

I always stick with a 50/50 mix. Run to much water and you dont have good freeze protection and it will boil and not cool as well. I would bet its the thermostat or maybe the radiators need a good cleaning..

 

i would bet that it is the thermostat. mine was doing the same thing, the thermostat was working according to the guage, i could see it drop when it opened. my problem was that the thermostat was only partially opening and restricting flow. the old one and new one were both the same temp (190) to open, after i put the new one in, took a trip and towed 13k home almost 5 hours and never went a stitch over 197. before i would run almost 210 at 70mph.

hope this helps!

 

I vote on the tstat too. Mine started running hotter at 60k miles already and that's what it was. I heated the new and old ones in a pot of water with a thermometer and the new one opened half and again as far as the old one at 211 degrees. Craig

 

Now when you guys replaced yours did you use any gasket junk or anything?
Just use the rubber band looking gasket on the t stat?

 

I generally use a small dab of silicone LUBRICANT and spread it over the O-ring. That allows the rubber to move and not get pinched during the tightening.

 

I run 60/40 being it can get a bit cold at night in the wintertime.

 

Got it done, It is better but not really what I remember.
It runs up to what you would think it 180-190 on the gauge for just a little then up to 200 and you can see it open, it will drop down some maybe in the 190-195 range but running 75 it will push it up closer to 200.

For the most part it never went above the 190 range if I was not towing on a hill or really getting on it.

Any changes in the fuel that could cause higher temps?

I did change oil, looked fine, changed fuel filter, looked fine..
Running and pulling fine.
Just started seeing the higher temps hitting 200-205...210maybe towing and staying at or around 200 for no reason I can find before I changed the T-stat.
Now it is lower, so the T-stat was some of it.

Maybe it is the sender.
Any easy place to add an extra check sender and guage?

My oil sender is doing to same crap that everyone elses is, running real high, set at a stop light is just above the lower line. Tested fine.

So some of you guys with 03 trucks, where is your gauge reading?

 

did a little looking today and found the foam that lines the airbox to the fender is gone, few small chunks in the air box but it looks like the air could be coming from under the hood. Could the air, being hot from under the hood make it run a little hotter?

 

maybe try a laser thermometer. shoot the thermostat housing as its about to open and hold it there to see how hot it gets. that might lead you towards the sender being bad or not, but i know, its hard to get accurate numbers from the dash gauge. i really like having my digital on my edge

 

I checked with a laser temp but it was after I shut it off and it was running 196 to 200.

Need to check it running as sometimes the temp will build when off.

Will do that in the am.

 

other things to consider...
as the radiator ages, they lose some of their efficiency. A new radiator will cool better than the same radiator with 5-6 years of run time.
Antifreeze concentration can be a consideration.
Pump pressure/circulation pressure can cause issues. Not sure if there is a way to check pump outlet pressure on these little engines and not sure if there is a published spec.
Check your temperature differential across the cooler... Also, check the entire surface area of the cooler to verify there isn't a section that is clogged with road grime and bug guts... Its hard to check sometimes due to the miltiple coolers, but take the time to check them all thoroughly... a flashlight and a buddy are usually required for checking the coolers.

 

"Antifreeze concentration can be a consideration"

Do they still make the gauges that tell you a % or a temp rating.
I wonder if the newer HOAT stuff I got if different for some reason.
I did use the correct stuff but no way of telling how much water is left in the motor....
I did see the the HOAT stuff is thicker and almost like a oil when new, not thin like water.


"Also, check the entire surface area of the cooler to verify there isn't a section that is clogged with road grime and bug guts"

Also looking into that. Getting one of the tools that fix the bent fins and make air flow better. Lots of bugs a rocks and road crap have hit the front over the years.