1990 Uhaul 17ft truck
C3 auto transmission.
10,000lbs empty weight. Had 2500 lbs loaded.

Usually it's all flat ground in Los Angeles, so I never get to see it go uphill. Is this normal?

It's filled with antifreeze, checked it 4 days ago.

Oil is full as well. It's usually blow midpoint temperature, it's rare that it even goes to the half point.

How high should the temp guage go towing this much weight uphill?

 

Starting elevation was 1096ft.
Ending elevation was 4000ft
Average MPH 39
Total distance from 1096ft to 4000ft was about 28miles.

Time it took to cover the 28miles was 8:40pm to 9:15pm = 30min

 

In case you guys are wondering how I know/remember this info, I have an android device on this truck. I track my crew this way. The app is called RTT2 (real time tracker 2).

It shows speed, elevation, records the route throughout the day. So I click a certain point in the route and it tells me what time the truck was there and all the other info.
I use this app about 50x per day. Super handy.

 

I'm betting you had that thing pretty much floored?

More fuel = more temperature; and yes, when you load it for quite a while you'll get temps going up.

I'd start worrying if you get to the L in normal, that should be somewhere around 230F I think. I know that if you ever hit 240F, the gauge will peg to H and the check engine light(I think) will come on.
You really don't want it to be at 240F, though.

I've personally hit 225F loaded going up hill on a long grade.

 

I see. I'll ask the driver just how high it went. After blowing up a rebuilt Isuzu engine last year (engine was 1.5 years old) due to my negligence (ran out of oil) , I want to make sure nothing stupid ever happens to my only source of income. I watch that ford like a hawk every 10min lol

 

With a U-haul rig, I'm guessing it's got a good transmission cooler? C6's, while bulletproof aren't exactly the most efficient due to not having a converter lockup. This = lots of heat.

Also, the other thing to worry about is EGTs. Usually not a problem unless you've turned up the fuel or added a turbo, but EGTs are what melts valves.

I'd be tempted to install a cheap trans temp gauge, and perhaps add a EGT gauge as well; it can't hurt.

One of these days you'll probably want to upgrade the truck some; I'm sure it could use a turbo with that much weight on the back. Get some extra performance under that hood and you'll be going up that grade at 70, not 40.

 

3am, truck just got back. I took the cover out from inside (it's a van) and there was green coolant on top of the air filter cover. It's also leaking coolant, smells like it too. I'll check it out tomorrow, but definitely leaking coolant from somewhere

 

The main hose coming from the top of the radiator (thickest rubber hose) feels like something is sucking or trying to suck the air/water out of it. Some kind of pressure is pulling.

 

You mean it's under vacuum? This is somewhat normal - When the engine heats up, the water expands, and some is pushed out into the overflow container. When it cools down, the water shrinks, causing a vacuum that then (should) cause water to be pulled back from the overflow.

I'd make sure your radiator cap is in good shape, your overflow tank is connected, there's no blockages in the overflow rubber line.

Other than that, make sure that all your hoses are tight, and/or perhaps replace them if worn.

 

the 7.3's run much warmer than the 6.9's did.it sounds like she's running fine to me.if she's under 240F (no engine light on) keep her to the floor and keep asking her for more.

 

The driver said
" It went all the way to H but when I let the gas go and went uphill at about 35 it went back down also the water in fuel light started flashing"

 

I had this happen this week as well with my f350. Did a 2000 mile round trip from Washington to California hauling 100 bales of hay. I noticed that if i put my foot in it going up grades the temp would go higher as the truck slowed and coal would start going out the pipe. If i backed off the throttle and the coal stopped the temp would go back down. If i down shifted and kept my rpms up it would have no coal and the temp would stay the same. The outside temp was about 106.

 

you need to drain the water separator.

your fuel screw is set too high.very dangerous.not only are coolant temps too high but exhaust temps are too.if n/a be extremely careful (you should turn the screw down).if turbocharged,adding an intercooler will let you use all that fuel so you won't need to back off the screw.
even if your engine still runs after hard high egt temp runs,your still doing internal engine damage that will slowly weaken and ware out the engine prematurely.beware of people who disagree with this as they more than likely have something to sell.

 

28 miles in 30 minutes is nearly 60 mph.
Climbing 100 ft/min for 30 minutes at nearly 60 mph in a 12,500 truck with a NA IDI is gonna generate a lot of heat...

 

Where is the water separator located? Can you post a pictures of what it looks like?