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slow tow/ over heating

2816 Views 26 Replies 8 Participants Last post by  AllOutFirefighter13
ok sorry in advance for how long this might be.
First off my truck: 05 F250 6.0L 80000 miles. Banks 6 gun tuner, exhaust, intercooler, intake, airbags.
I just bought a new fifth wheel(07 raptor) 33' 10,010 claimed dry weight. I was pulling it across interstate 40 through arizona into californa. The temperature in cali was about 105* going through the desert.
Now to the story. Any of you who have driven that way know of the hills and win. Up two long hills I lost speed from 72 down to about 35 and into third gear. I was only at about half throttle cause every time I gave it any more the engine temp would run to high (230*) if
I kept my foot half throttle, with the rpms at about 2500, the fan would keep it down (220). I was passed by every semi, a car pulling a van on a uhaul trailer, and a (97) chevy suburban pulling what looked to be about a 28-30 ft travel trailer. I had some coolant puking going on. I put about 3/4 of a gallon back in, even had the a/c shut off and the windows down. is something wrong or is that just the best my truck will do? /ubbthreads/images/graemlins/shrug.gif any comments would help. Thanks- Dan
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230F or even 234F coolant temp isn't going to kill it.

But the fan should be fully-engaged by then and pulling it down.

Can the Banks PDA control fan engagement?

That's one of the things that worries me about the aftermarket codes and chips combined with the Visctronic fan -- there's temptation to muck with the fan cal to "make more power", and that can lead to problems when towing. But I don't know if Banks did so.

Check your heat exchanger stack for bugs, dirt, grass, small desert critters, too, while you're at it. That's become an annual maintenance item for me.
Okay, sounds like the fan is doing what it's supposed to be doing.

Still check the exchangers for crud buildup. Just don't hit them with a power washer as it'll flatten the fins, making it worse. I use a shop vac to get the loose stuff, then Simple Green and a garden hose (hose from rear to front) to get the rest.

Hmm... you're reading the temp off the Banks, so the sender is the OEM one in the right spot... Ah-HA! Got it! /ubbthreads/images/graemlins/biggrin.gif

The EGR is working and that's putting heat into the coolant above and beyond what the engine is kicking out. That's mostly a function of the part-throttle operation. Next run, try staying in it for a bit and see if it stabilizes. If it keeps climbing, back out before coolant temps hit 240F, but I suspect it'll stabilize once the fan gets things caught up.

But I'd still clean the exchanger stack.
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where exactly or what exactly are you talking about when you say heat exchangers?

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Those big finny things right behind the grille that exchange heat from the vehicle to the atmosphere.

As far as the thermostat goes, I don't think that's the problem or you'd be seeing it at high speeds as well. It still sounds like an airflow restriction situation combined with EGR operation to me.
Ummm... when the system pressurizes as the coolant expands, the top hose will get hard. It's supposed to do that.
Okay, let's back up a second.

16 lbs is the relief rating on the pressure cap, give or take a 2-3 lbs. At this pressure, it vents to the atmosphere. Or at least it's supposed to. Some coolant may escape at that time depending on its proximity to the cap when it vents.

If you're concerned that there's too much pressure in the system, check the cap operation as its relief valve could be stuck closed. In the grand scheme of things, though, more pressure is good up to the point where you pop something, probably a hose/clamp joint. Each psi of pressure raises the boiling point of coolant 3 degrees F. So a truck with a higher system pressure would be more resistant to overheating/boilover than one with a lower system pressure.

This does NOT mean we should all find 25psi pressure caps for our trucks, of course. That would be silly. The system is designed to operate within the envelope provided by 16 psi above atmospheric pressure (272F boiling point for 50/50 EG/W coolant).
Got a related question, since the topic of EGR added heat was mentioned earlier. With the change over from the 7.3 to 6.0 did Ford dramatically increase the capacity of the cooling system to cope with the EGR and higher HP levels of the 6.0?

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Yep. Don't have all the changes in core face area in front of me, but just for an example, the fan went from 23.25" diameter on the 7.3L to 26" on the 6L. Bigger fan = more air movement.

I haven't had any overheat issues, but I've read that the 6.4 has a significant increase in radiator size and water pump volume. Presumably this is to compensate for the that huge EGR setup?

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Yep. I know what all the differences are between the 6L and 6.4L, but I'm not at liberty to discuss the actual numbers (I like my job, and I'd like to keep it). The water pump was upsized considerably (and is completely different than the 6L setup -- there is no possible interchange between a 6L front module and a 6.4L front module).

But the assortment of additional heat loads, primarily from EGR, is what drove most of the changes.
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I'll pull the top of the radiator loose (two bolts) and tilt it back to get to the back of the CAC, and clean the rad itself through the fan shroud opening. Because of where it's located (at the rear of the stack), the rad doesn't usually get too much buildup. Mostly, though, what I find when I pull the rad loose is a bunch of grass between the rad and CAC! This is scooped/shop-vacuumed out before moving on to the next bit.

The first exchanger is the AC condenser.

I don't so much spray as much as flood the back of the exchangers with just a standard garden hose.. If you really want to do it, yeah, pull the CAC out, but I have so far not done that with mine. Getting to the back of the condenser is tricky without pulling the CAC or the condenser itself loose from the front of the CAC.
Two of those bolts may have been for the fan shroud. You found some bugs back in there -- not surprising! /ubbthreads/images/graemlins/smile.gif

Okay, what I sometimes do with persistent stuff is give it a good soaking with whatever cleaner I'm using -- Simple Green, what have you, and use a VERY soft brush and gently brush some of the accumulated crud loose. Again, the risk is that you bend the fins and make the situation worse instead of better, so take your time and be gentle.

Good luck!
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