Hello, while I have referenced this forum many times in the past for many questions I have had about my Ford vehicles, this is my first post. I have a 2006 F-350 FX4 Lariat Tow Boss. The truck has a 6.0 PSD with 4.30s gears. I purchased the truck recently and have been incredibly happy with it aside from the concerns I will address here. The truck has been fully and entirely bulletproofed including: New Ford Remanufactured cylinder heads & Injectors, new ICP, Water pump, ARP head studs, Bulletproof Diesel brand EGR cooler, FICM, and Oil cooler as well as oil filter. All lines/hoses were just replaced as well as radiator and fan clutch. I have records and photos to show all this work was done. The truck sits at 184K miles and has been treated very well for its entire life. I don't believe there are any special tunes for power, however it is set up to just slightly roll coal on takeoff. I tow a 2006 Weekend Warrior CL4005 40 foot triple axle toy hauler. It's well known that Warrior lied on their trailer weights and so I've always used the posted max GVWR of (15K) as an estimate of how I roll rather than paying any attention to the clearly untruthful unloaded weight of just under 13K (there's no way a 40 foot triple axle T/H is that light). I boondock and do tend to tow with full tanks which adds over 1300 pounds to my load. I also bring one or two of my golf carts which even combined aren't over 1300 pounds and are significantly lighter than any RZR or other offroad vehicle this trailer was engineered to carry. Based on rear axle weight pin weight is estimated to be around 3K. The truck squats more than I would like but in numerous trips including an over 1000 mile road trip it has always felt incredibly stable and grounded. I have about 2 inches left to the bump stops. All shocks were just replaced.



As for my concerns...I started seeing some issues on my recent 1000 mile road trip. It started while I was driving on flat land in Arizona. Temps out were hot, well over 100 degrees F. Fan was running constantly and I could feel the power loss from it. Even on flat ground the fan was absolutely screaming and the truck felt stressed if I tried to push for over 55 MPH. Even with a load that heavy on that warm of a day I think a fully bulletproofed 6.0 should be doing a little better than that. I saw a massive grade ahead (11% for 3 miles). I floored it and managed to get to about 60 MPH by the time I hit the hill but my coolant was already fully saturated. Immediately I lost about 20 MPH and was down to 40, still floored. This is a route many RVs take and I was struggling to keep my buddy with a 22 foot motorhome (6.0 Chevy gasser towing 25 foot enclosed trailer with 2K pounds gear and RZR) in sight. I continued to lose speed as coolant temp approached 130 and then 140. At this point floored I was going 30 MPH up the hill and I was concerned if I pulled over I'd never be able to get moving again. If I backed off throttle I instantly lost tons of speed. As I neared the top of the grade the "check engine temp" warning came onto my dash. For the entire grade I had the heater on full blast to help pull heat from the engine. According to the exterior temp on the truck's climate control it was over 120 degrees out but I'm not sure how accurate that is or if it is affected by how close sensors for that are to the engine. It felt like the truck was being torture tested and I really wasn't comfortable. Once I crested the grade and pulled off, almost immediately my coolant temps recovered and dropped back to around 212. Unfortunately I haven't installed gauges so I only have an OBD readout on my phone for coolant temp and can't monitor anything else. For the rest of the trip coolant sat at around 216 average with temps outside averaging 113 F (Arizona desert is HOT). On every grade, even small ones, semis were passing me like crazy and I had to be to the floor to keep over 50. On some of the larger interstate grades I was only holding 45. I do want to add, unfortunately despite using the highest quality fluids for everything, the previous owner did use Motorcraft Gold which I still haven't had the time to flush out and replace with a proper diesel coolant yet. With the bulletproof diesel coolers and good maintenance I know this may not be the biggest issue but it is something that does concern me. The Gold Coolant is brand new.



On my route back, I had the same constant fan roaring but hills weren't as bad and I was usually able to stay with traffic on grades. Outside temps were still around 113F according to truck. Through one grade on I-40 in Needles where outside temps were actually closer to 120, I started thinking the semis were going really slowly all of a sudden. When I looked down I saw I was actually going 75. I was in overdrive and it felt like the truck still had even more in it. The grade was about 3 miles and just as steep/long as most of the other rolling hills on the 40 in that area where I was previously struggling with much over 50. During this time, coolant was at around 213-215 average and fan was still often at full blast but did go off for a few minutes occasionally. During this time I also had the AC on inside and it was blowing very cold. I was really impressed with the truck in those moments. For the next couple rolling hills after this the truck was also great but it soon felt like it had lost a lot of performance again and was behaving the way it did before. It was once again a struggle to keep coolant under 218-219 and it was frequently peaking into the mid 220s. Because of the excellent performance for a portion of my drive with the same conditions I really believe the truck might be going into some sort of a derate mode or something and cutting fuel pressure because it believes it is overheating. As a side note, trans temp was no issue during any part of the trip. I'm curious if anyone has had issues like this before or not?



That trailer is HEAVY. I got it weighed yesterday and turns out I am WAY heavier than I thought. Clearly even the MAX loaded stickerGVWR of the trailer is actually below even the minimum true unloaded weight. My combined weight with my carts in the back and half a tank of water was 25,540. The max GCWR from Ford for the Tow Boss is 26K. I'm scarily close to the max rating of the truck and would exceed it with full tanks. I am still around 2K pounds below both GAWRs and I'm below payload capacity significantly but yet I'm 800 pounds short of truck GVWR and literally right at GCWR. This does concern me and I was really hoping for significantly more breathing room though I know on this generation of truck many were able to tow quite a bit above these numbers without serious stability or braking issues. I don't want to do anything dangerous and want to be sure my setup is safe. Beyond just having enough power to avoid being an obstruction to others on the road, I want to be sure my chasis and braking is up to the task. Because of how well it tows around town as well as that spurt where it literally felt like a different truck pulling up that grade in 120F at 75 MPH with no issues and lower coolant temps than most of my trip, I'm wondering what you guys think is going on. Back in 2006 there really weren't many options for a bigger truck and most weren't towing campers with MDTs or semis. An F-350 Tow Boss and large Weekend Warrior was a very common setup that worked great for many. Is it just a little less truck than ideal, or could I be having some sort of an issue? Thanks in advance!

 

First thing on the agenda is to get yourself a way to monitor all parameters to include EGT and Fuel pressure, which are standalone gauges. Unless I misunderstood monitoring only ECT is definitely not enough.

With the BPD air to oil cooler you shouldn't have to worry too much about deltas but I'd get rid of that gold coolant as soon as you can.

You're seriously asking for trouble towing that heavy in extreme heat "blindly" with no gauges.

We pretty much have the same trailer, except I am SRW. I definitely do not have any issues you described pulling similar hills and I am NEVER pegged to the floor to maintain speed.


" I continued to lose speed as coolant temp approached 130 and then 140" - typo? I am guessing you meant 230-240?

 

Thanks for the reply. Nice to see someone running a similar rig. I'm a big fan of those older Weekend Warrior trailers. I completely agree on a better monitoring setup. IMO towing a setup like this without gauges on a 6.0 is like going to church without a Bible LOL! I am familiar with the correct type of gauges. That's on my list right after ditching the gold coolant. Ultimately I was debating whether I wanted to make that big trip at all without a good way of monitoring the truck as I purchased it recently and haven't had time to do much but it was a family invite and included folks who likely won't be able to make it up again. I was expecting interstate all the way up but the group lead ended up deciding to take an alternate route to stop and see family. That's how we ended up on the "torture test road."

Glad to hear the MC Gold isn't as big of a deal as I thought it could be but that's still not changing my plans to ditch it ASAP. Previos owner had coolant overfilled (he sold his trailer and never did towing so don't think there was time for damage to be done) and I drained it out. I left it just a bit above the minimum line since I know today that line is considered a good target level. I was able to firsthand see how crummy that coolant is though as it left a nice layer of flaky crud on my storage container when I got back from the trip.

You're correct on my typo for coolant temps. Glad to know your rig handles it well. I had a feeling something was off and causing the truck to decrease power. I did run my codes when I got up there and the only code related to the engine was the one for fan speed. I find it hard to believe there is an issue there as the fan clutch is brand new. Also got random code for dash backlighting or something and door chime, which also make no sense as the door chime works and the dash was relit by Circuit Board Medics.

 

Forscan is the best cellphone app to read codes; I’m sure you have some.

From a left field gut call, it might be a sporadic turbo issue, which raised your engine temps and got the PCM to defuel.

 

Running those kinds and temps and loads I would definitely be leery of the Gold. The biggest issue with it was the high temps from the EGR cooler causing silicate dropout which plugs the oil cooler. Restricted oil cooler flow -> less flow thru the EGR cooler which makes the situation even worse. You are towing heavy with high ECTs and high EGTs so definitely a recipe for issues. Get rid of it ASAP!

And it could be defueling from high EOTs. You don't know the health of that oil cooler without monitoring it. Just because it was changed doesn't mean it's good.

At least it sounds like your fan and cooling system are up for the task. Max GCWR at 120F up long hills, Holy moly!

 

He doesn't have an oil cooler

 

I would never venture into any sort of hell that had those temps, and I'm only about 21k GCVW, but I've driven that some of those big climbs in AZ (in the winter) and always held at least 55.

In addition to an EGT and fuel pressure gauge as previously recommended, you might want to put a 185 t-stat in there. I have them in 2 of my trucks and really like them.

 

The Gold coolant is a big issue, even without a coolant based oil cooler. It just is not robust enough at extreme temperatures, new or not. It can precipitate out solids and plug up in any heat exchanger. Temps inside the engine on metal surfaces (skin temps) can be quite a bit higher than the bulk circulating fluid. This is very hard on the Gold coolant.

The engine was programmed to dramatically reduce power as coolant temperatures got to 230F. The power reduction in the stock programming begins at about 221 F