So I took my truck for a nice drive today, burned up almost a whole tank. I would run at about the middle of the "M" in "TEMP" at 55mph and at the beginning of the "P" at 65mph. I'm expecting higher than stock, but how much higher than stock? Around town runs just inside the "normal" range to the midway point, depending on load. It fluctuates a lot.

Going uphill, mountainous road here in Alaska (Turnagain Pass), it would climb to the end of the "P" or just past the "P".

This is a 74 flatbed unloaded F-250, 4.10 gears, NP435/205, with 315/75R16 (34.6") tires. I don't have a tach yet, so can't tell you the engine speed.

What temps do you guys typically get under normal and loaded conditions?

 

thats about normal. also depends on what degree thermostat your running. one in my 76 runs about 195-200 all day long driving or idling. looking at the guage as long as its within the O and L its fine. anthing over the bar after the letters i would stop.

crap i see yours just says temp. anything after the P i would worry about

 

Running a 160 t-stat. The fans have to be on all the time, they come on at 195 and stay on, unless I do light in town driving and idling.

The cooling system will cool down quickly once the load is taken off, but hold the load at 65, and it stays in the upper end of the gauge. Problem is this is an unloaded truck, but I plan on doing a little towing with it. I don't know if the cooling system is going to be up to it or not while towing.

I'm still running the factory I6 radiator, it has dual electric fans and an intercooler in front of it. The fans pull through the intercooler, then radiator on the upper 2/3 portion of the radiator. Lower 1/3 portion of the radiator is free air flow, but behind the bumper.

I'm wondering if an oil cooler will help, I know it'll help my oil life.

 

most I6's that i have seen in the past 5 years have ran about that temp. if your running dual elc. fans and its still up like that i'd check your radiator to see if the cooling rows aint clogged. basically take the cap off while its warm and watch for flow but watch out and make sure the system isnt pressurized and fry your face with hot coolant. had that happen a few times. if all is flowing good in the radiator i'd say maybe a fan isnt doing its job compared to the other. or maybe some internal blockage.

 

You can't use the stock temperature gauge to correlate the temperature of your engine. There's no way to quantify observations such as "partway between the O and the R," etc. "O" on one person's truck may be different than the "O" on someone else's. Furthermore, the stock sending unit is subject to drift over the years. The stock temperature gauge is only meant as a "go/no-go" warning mechanism.

The only way to get an actual temperature reading is to install an aftermarket mechanical gauge that places a sending unit directly in the coolant path, and uses a needle to indicate the actual temperature number.

Lastly, you shouldn't run lower than a 190 degree thermostat. Running a thermostat below that will severly accelerate engine wear, especially at 160 (one of the lowest you can get). The stock thermostat would have been 192-195, and that's what you should run.

The net of it is, to properly diagnose your temperature issue, you first need to diagnose it with actual numbers. You may or may not actually have a problem, but until you can really get a glimpse of where the temperature is actually sitting around, it'll be hard to know where to go.

 

I agree, get a actual gauge and see what it reads. On my truck, I had both the stock gauge and an autometer gauge hooked up and my stock gauge would read between M and P while my autometer gauge would be around 195.

 

Well I kinda want to see if my stock gauge is working "normally" compared to others, but your right, mine might be skewed to others and the engine is actually its either hotter of cooler than other that have the same stock gauge reading.

I'm running Megasquirt, so I have another temp gauge at the outlet of the cylinder head (inline with the heater hose) It reads about 215 at around the the same points as the stock gauge as described in my first post. I have changed a couple things, so maybe its more normal now. I'll have to bring the laptop with me and find out.

I don't really want to keep another gauge in the cab. I just think they are clutter sometimes. If I can get to know where the stock gauge stands, then I'm happy with that.

The radiator is fairly new with not very many miles on it (maybe 5000?) The fans are new as of when i converted to turbocharged. I can tell when one doesn't work. The cooling system gets hot.

Why would a 160 thermostat cause accelerated engine wear? Running too cool and richer mixtures all the time? I could probably put the the 195 back in at this point and see no difference because I am always running above 195 anyways.

I'll have to manually check the temps to see where exactly it stands.

Sender location also is a key in determining proper temps.

 

Drove it a bit more today. Got some different results. It's a bit colder today, but not that much colder. Fan switch closes at 195. When my ECM temp sensor read 195, 2 seconds later the fans came on. I was surprised how dead on it was. That's a decent sign of accuracy.

Anyways, I monitored my ECM coolant temp under same conditions as yesterday. The stock temp gauge consistently ran lower all the time and at 55 mph, according to the ECM, it read 203. At 65 mph, it read 208. It was very steady and consistent. So either I was running hotter yesterday than today for some reason, or my stock temp gauge is erratic and changes between warmup cycles.