Extended Engine Operating RPM's and Towing on Grades

[scotth92]

I'm the proud new owner of a 2002 Excursion PSD 4x4. The principal reason for the acquisition was overheating my Expedition while towing grades along I-70 in the Colorado mountains with a 6500lb trailer. To ensure I don't repeat my errors, I was interested in checking on extended engine operating RPM's.

I've done my first test tow, and the engine seemed to operate between 1800-2000 rpm's at highway speeds. It occassionally dropped to 3rd on short grades and operated between 2500-2750. Given my experience with the Expedition, that made me uncomfortable and wouldn't be a range I would want to operate in for an extended period.

What have people's experience's been? If I've got the AC on, a family of 4 with 100 pounds of gear in the Excursion PSD and 6500lb trailer, what RPM's can I comfortably operate the engine at for extended grades in the mountains?

Thanks in advance for any advice and/or personal experiences.

[Pocket]

The 7.3L PSD tows better at 2500 rpm's than it does at 1500. Contrary to your old Expedition, these engines can run all day long at higher RPM's. The only drawback is fuel mileage drops.

The cooling system on these engines is designed as overkill. The only time you'll ever overheat a 7.3L is if your water pump fails, or you leak all your coolant. You can tow as heavy as you want, the engine water temps will be fine.

On the other hand, the concern with diesels is exhaust gas temps (EGT's). These engines need lots of cool air. The general consensus with the 7.3L is to keep post-turbo EGT's below 1250. If you go above 1250, it can only be in short bursts. Don't tow up a mountain grade with EGT's over 1250 the entire time, otherwise the pistons will melt.

If your Ex is bone stock, it probably won't have an EGT gauge. That is fine, because in stock configuration (no chip or tuner), it's almost impossible to sustain EGT's over 1250, unless you have a problem somewhere. It's still recommended to have an EGT gauge, even for stock trucks, particularly if you tow.

Last thing, I live in Parker and drive up I-70 all the time. I know traffic changes and speeds on the highway change. If your truck is shifting in and out of overdrive like it's hunting for gears, hit the O/D button on the shifter stick to lock out O/D and keep it in 3rd. Constant gear hunting will kill the transmission in no time. It's best to run at higher RPM's in that case. The stock transmission is the weakest link on these trucks, so take care of it.

By the way, 6500 lbs is nothing. These trucks can tow more than twice that up the mountains.

[F350-6]

Welcome to FTE. Curtis has given you good advice here. The only thing I can add is come back and tell us how surprised you were after your first trip towing. Pulling that trailer with your new ride will be like changing from a golf cart to a car.

[strokin_it7.3]

Yep, these engines are designed to be run at anything under 3400rpm at full load, and it can "take it". You'll get lower exhaust temperatures and more power by taking it out of overdrive and "lettin 'er eat" however the only thing your fuel mileage will go down the crapper.

[scotth92]

Curtis/Chris/Kris - thank you very much. That eases my mind substantially. Last trip out we overheated 3 times in the Expedition going to Breckenridge and back - and that was with a freshly flushed and filled radiator from overheating 2x the trip before... We are leaving for California (Disneyland) next week and no way was I going to attempt that in the Expy after all those problems.

It does appear to be a stock Excursion Limited PSD - except for the new radio I put in it (Nav/Bluetooth/Ipod adaptor/Rearview Camera)


It doesn't have an exhaust temp gauge, but it was interesting it has a transmission temp gauge. I'll have to look in to the exhaust temp gauge.

As far as towing. Ummm, yeah - shocking how different it is. I read all these posts from folks saying "I don't even know it is back there!". I always just rolled my eyes. From my experience towing with the Expy, I couldn't possible imagine that to be true. Switching to the Excusion PSD - it is true...

1) Virtually no acceleration or operating RPM changes when towing
2) I didn't feel the push and suck from 18 wheelers
3) Healthy cross winds (20-30mph? - I'm guessing) where only noticable because you could see the trees bending and hear it coming across the windshield. The truck and trailer didn't budge.

And that was with a terribly mis-configured hitch set up that was meant for the Expedition on a 25 mile tow to the dealership to get it fixed. Coming back after getting adjusted properly, it was even better.

I do very much appreciate the feedback. These past three weeks have been nerve racking with all the problems we have had overheating. I'm still a little nervous because of the unknown of the new to us used Excursion - and my first experience with diesel. It is a 2002 with 53k miles on it. I'm probably going to take it in on Saturday and get the 60,000 mile service and the radiator flushed and filled just to be safe since we leave next week.

Disneyland, here we come!

Scott, Holly, & 2 young girls (4 & 1)
2002 Excursion PSD 4x4
2009 North Trail 31QBS
Prodigy Brake Controller and Equalizer Hitch

[F350-6]

If you're going on a long trip, you do need to be aware of the weakest link on these engines. It's called the CPS and can leave you stranded. Fortunately it's a cheap part now. You can get it online from one of our sponsors for around $16 or at your local dealer for $30. I'd recommend you pick one up and throw it in your glovebox before the trip.

Here's instructions on how to change it. Welcome to guzzle's CPS R&R Web Page

[Kwikkordead]

Welcome to the 7.3 PSD family.
You have nothing to fear pulling that "little trailer".
They used these engines in full sized school busses and they ran forever.
My truck and trailer weigh 24k fully loaded and I WOT up hills all the time.

[SuperDoodie]

These PSD can handle a lot! I just returned from a short vacation and towed up Lookout pass (the pass between Montana and Idaho border) at 65 MPH pulling a 38' 5th wheel toyhualer that is 16,000 lbs loaded.

[Pocket]

I'm probably going to take it in on Saturday and get the 60,000 mile service and the radiator flushed and filled just to be safe since we leave next week.

You don't need to flush the radiator fluid if it has the gold coolant. The gold stuff is good for 100K miles and is completely maintenance free up to that point. If it's green, then yes I could see a flush. The green stuff requires regular maintenance, and since you bought it used who knows if it was done.

As far as service, for these trucks they just need regular maintenance. Oil change, fuel filter change, and at 60K probably a trans filter change (drop pan, swap filter, refill fluid). There really is no tuneup required on these engines like there is on a gasser. Just keep up with maintenance and you'll see over 300K miles without breaking a sweat.

Also, I do agree about getting a CPS and keeping it as a spare. When they cut out it leaves your engine dead as a doornail. Good thing is it's so easy to replace.

[Pocket]

Oh, one more thing.... Since you live in Colorado, feel free to check out the Colorado Powerstroke Club. There are a few members of this board who are also members of the COPSD club. We have events and get togethers from time to time, like racing/sled pulling/Hooters/etc. Colorado Power Stroke Club

[Mark250]

6500# is child's play. My flatbed weighs 6000 empty. Enjoy your trip & don't worry about a thing.

[scotth92]

Okay - I'm back. Thank you to everyone for all the reassurance. I was still white knuckling it a bit since I was overheating at every pass before with my gas Expedition, but here was my experience in the 2002 Excursion PSD with a 6500# trailer and 2 weeks of supplies for a family of 4:

With the 3/4 ton Excursion, I ran all flats and many minor grades at 70MPH in 4th gear and was totally rock solid minus some heavy cross winds at one point. It was so nice to be able to do this. At one point on a downgrade gathering speed to a pending upgrade in Utah, I crested about 80 at the bottom - still rock solid but nothing I would be interested as a routine operating speed.

I-40 West between Lake Havasu and Barstow - 2 extended grades - both of which had semi-trailers on the road side - 93+ degrees:
3rd gear - 2750 RPMs - 60+mph

I-15 East - Mojave Desert - 16 mile infamous grade with the "turn off AC to avoid overheating" sign - 104 degrees:
3rd gear - 2500 RPMs - 50+mph

I-70 East - Vail Pass - 80 degrees:
3rd gear - 2500 RPMs - 55+mph on the first half, 60+ on the second half

I-70 East - Loveland Pass/Eisenhower Tunnel Approach - 80 degrees:
3rd gear - 2500-2600 RPMs - 60-62mph the whole way* - and get this - I passed a BMW X5. I thought that was pretty funny. The * asterisk is that I did start to get some noticable temperature rise just as it closed from 3 lanes to 2 and we moved into the tunnel. The moment it moved from "I think it might be slightly over normal operating temps" to "I can definitely see the gauge moving", I backed it way down to 1500 RPMs and 40-45 MPH (I honestly didn't care about my speed at that point - I was mostly concerned with watching the engine temp gauge). Within 60 seconds - probably less - it noticably and obviously dropped right back to normal operating range and never bobbled again. Of course, it's downhill for 40+ miles at that point...

While this was fun - particularly passing the BMW X5 - it was also slightly concerning, so I'm hoping for a few pointers:

1) The AC was on - including the rear aux A/C at 1 bar out of 4. Would turning off the AC and/or rear Aux A/C at 80 degrees exterior temp make a difference?
2) Was 2600 RPMs too much for that sustained of a grade? If yes, could I maintain a slightly slower speed in 3rd gear, such as 2200 RPMs/~50mph, or would I be missing the power band?
3) People have mentioned an Exhaust Temp Gauge. Would I have seen a temp rise on this gauge first and been able to react sooner? I'm about 90% certain I'm going to track one of these down, I just want to validate that it would have helped this situation which is the worst I should ever encounter with 2 weeks of supplies being the heaviest I would load.
4) It was mentioned to me before to "improve the airflow" and I'm beginning to appreciate this. Is this something as simple as walking into the dealer and stating "I want the 2002 Ford F350 PSD air flow set up on my my 2002 Excursion PSD" or is this something I have to find a reputable after market dealer to help with?
5) I keep hearing about "Jody's chip". Would this help with engine cooling or just add power? I'm really unconcerned with added power - I have plenty for my needs - I'm more concerned about ensuring I can keep running at safe speeds without overheating.

Again - thanks for everyone's feedback and I look forward to any advice. I am really happy with the Excursion PSD. I could probably do nothing and just back it down a little, but I am interested in understanding the options available, so thank you.

[willeo6709]

the EGT gauge really is life and death on a towing diesel. Its been a while since I ran a diesel with one... someone will correct me.. but anything egt over 1200 for prolonged periods is probably cause for concern, with about 1400 an absolute max I believe. Basically egt tells you how hard you are working the engine in real time. Others have said that mechanical pyrometer engine coolant and trans fluid temp gauges are must haves as well. The stock gauges don't react as fast or as accurately as they could. I would say the ac is not a major load on the engine... but I preface that by saying to make sure you keep your coolers clean. another egt lowering item is an aftermarket plate style intercooler. It lowers the temp on the intake air for a more dense( read more o2 for lighting the fuel ) to get more complete combustion in the cylinder where it gets converted to HP.

[scotth92]

Thanks, Willeo.

I did some poking around and reread this thread and some others. It looks like my cooling system is the same as an F350SRW since we have the same GCVWR. I'm also certain I will add an EGT gauge. I tracked down this link that looked promising:
ISSPRO Gauge Kits for Ford Powerstroke from DieselManor

[white Buffalo]

Those are very popular gauges and many folks have them in there PSD. The stock (in dash) tranny gauge isn't very good. The aftermarket trans gauge that comes with that kit is very simple to install and does a much better job. Dieselmanor is a great place to get gauges from, there kits come with everything needed for a complete install.

There are a few different air intakes to choose from, just search the site. The ford AIS, AFE and Kwik 6637 are the 3 most popular. You should consider an exhaust upgrade or "muffler delete" to help drop those EGT's while towing. You are doing it right by installling gauges first. That way you can see the difference after adding more modifications along with protecting your engine.

All the above is definitley recommended before adding a chip. In addition check out Tony Wildman's Chip at www.totaldieselperformance.com. He has made me two excellent tow programs that keep the EGT's nice & cool and help automatically decelerate the load on the downhill slopes. Plus chip reburns are free after you do additional modifictions to you truck, FYI down the road stuff.

The Colorado Powerstrohe Club is a great bunch of folks. In fact there was a bunch of them out at truck fest this past weekend. You have Rockin S Performance right in your backyard. Rocky is a great guy also.

Welcome to the site and enjoy your new hobby/obsession!