For 19 years of owning a 4.88 geared F550 that pulled like a bull elephant, but always generated more heat than the cooling system could handle, what finally made the difference was deglazing the water pump pulley. After that, no belt slip. I have a Hayden fan clutch in there as well and it locks up good enough to keep the temperature gauge from rising, even when pulling the 13k 5th wheel up some hills north of Las Vegas on 93 that requred full throttle just to keep it from dropping speed. EGTs would be 1200-1250 and the boost was 21.5 for miles before the ground would level off, and the speed would recover from 70 back up to the 72 that I had the CC set at, and the power requirements would drop off. Some long, gradual hills there that really put the drivetrain to the test. Through all of that, the engine never overheated. Outside temps were probably around mid 70s at the time.
I really wish that I had known about the deglazing of the pulley 15 years ago. I would have saved me about a dozen migrane headaches.

 

At what oil temp do you notice the fan doing anything? That’s always been a bit of a mystery why I can never hear it kick on hard at a certain temp and hear it roaring away.

I’m pretty sure I’ve had a worn and glazed pulley before that was causing belt slippage. Replacing the pulley fixed it and now I’d never reuse one when doing a water pump job. Nor the fan clutch which is why I replaced them both. Shame on me about reusing the old cap. I go pretty easy on mine it sounds like compared to some you guys…I drop as many gears as it takes to maintain a nice easy partial throttle 2000-2100 rpm and try to keep the temps down so this is bumming me out🤣

 

Sounds like the coolant cap is the problem. I'd start there.

 

With 4.88 rear axle 70 mph = 2700 rpm give or take a few in OD. There's no loafing along at 2000 at any time unless I want to only go 50 mph.

 

Speaking of clutch fans. Just ran across this and might be interesting to some. I know it's not a 7.3 clutch and it's electrically operated but interesting none the less how a clutch fan operates. Our 7.3 fan is proabbaly closet to the same just uses the little heat cool thing to rotate the little door for the fluid inside.

https://www.tiktok.com/t/ZTL9d4K27/

 

Is Scotch-Brite pads and brake cleaner still the preferred method for deglazing?

 

I use a wire wheel on a 4" angle grinder

 

I walked down to O’reily’s and picked up a new cap before getting going this morning. It’s identical to the OEM unit right down to the part number and country of origin as you can see on the underside shot. Old cap took very little effort to back it off and this new one felt like it clicked into place very solid. Without doing anything too scientific I am guessing that was part of of the problem…the spring tension on these gets tired if they’ve been on there too long and that’ll tell on ya at some point.

For the remaining 69 mile journey with that trailer this AM, it stayed in the 215-221 EOT range depending on how the terrain was treating me and how good of a roll I was getting. Mostly flat and calm with 55-60 degree ambient. Just a couple little spots where I had to drop a gear and take it easy. This is an 11k 5th wheel keeping it at 65-70 where possible. Did have a little sprinkling of coolant on the underside of the hood when I arrived in that triangle spot:





Possibly a little too much in there for this warmer weather? Isn’t it pretty well understood that the “full-cold” line is actually too full on these systems? I usually keep it below the seam weld line. Other thought is that I also reused that coolant bottle when I spiffed up the cooling system about 17k ago. It’s been on there just shy of 100k miles since May of 21 when I did the water pump the last-last time. And the coolant cap had been on there even longer…about 140k since 2/2020. I’ll have to keep an eye on that.

 

my '02 Excursion had a loose feeling coolant cap on it when I bought it,
I forced the auto store to order me up a genuine Ford cap, took a week, but it was worth it.

it is had to twist when it gets tight and starts to click.

 

I used a sandpaper wheel on a dremel.
It worked so well that it took the glazing off of the smooth part of the serpentine belt in about a minute of operation. ZERO slipping now, and no sign of abnormal belt wear after putting about 7,000 miles or so on the "new" setup.

 

Best part is the mod did not cost appreciable belt wear. Makes sense tho; ain't slipping, ain't wearing.

 

Whelp, she overheated for real this time pulling the grade on I-80 eastbound about 8 miles east of Laramie, WY. Oil crested 242* or thereabouts and all hell broke loose. Huge plume of white smoke comes billowing out from underneath the hood and truck. I get her pulled over…it’s idling fine and EOT comes down into the mid 220’s and I shut it off and pop the hood. Whole engine bay bathed in coolant and bottle’s totally empty. Makes what happened Sunday afternoon look like a minor hiccup by comparison.

The new cap I put on Monday morning seemed to help but that fan clutch I am guessing ain’t cutting it under super challenging conditions like that. 12,000 lb 5th wheel this time…was doing pretty good from La Grande, OR where I picked it up. Problem solved I thought. Only 40*F and even had the heat on full blast so clearly something ain’t right.

I’ve got Loves bringing me coolant so we’ll see what happens when I refill the system and fire it up.

If you start to smell coolant in the cab it’s time to pull over immediately because it’s venting out the top you’re about to boil over and end up on the side of the road. First time it’s ever happened to me driving anything from a car to a tractor trailer.

 

That sucks. Hate to hear that. Hopefully you can get it filled back up and continue on your journey with no real harm to the engine.

 

Is your fan oriented correctly?

I saw another post recently with a photo of an engine fan that was mounted backwards, which is what made me think of the possibility.

I didn't follow the thread, but it appeared to have been an inadvertent error made in the process of replacing the fan clutch.

This isn't to say that you installed YOUR fan backwards. It is just another item to rule out, in the course of figuring out why your engine is not rejecting enough heat.

 

Plugged fins? Airflow has to pass through the charge air cooler and and AC condensor before it even gets to the radiator. I've had mine apart and pressure washed from the rear side twice since I bought the truck and it makes a world of difference every time I do that.