I pulled a 15K lb 5ver from Phoenix to Flagstaff last weakend in 115 degree temps with my 2003 Duramax. I could not push the motor very hard at all, 1800 to 2200 rpms all the way up at 30 mph on the big hills (two of them if you know the route). If I got into it to get speed up (2500 rpms or higher) the engine temp and tranny temp started to climb pretty fast, engine temp was right at 3/4 (240 degrees) and tranny temp was around 250 degrees, also around 3/4 when climbing the hills.

My plan is to add the PPE Xcelerator kit to get more power, but add a water methanol injection kit to keep temps down. Anybody have an opinion on this, or do the same thing? I just want to be able to climb the big hills at 2500 to 2800 rpms without boiling the engine over, or are these temps I was seing normal and they will stay there and not keep climbing if I hold the throttle at 2500 to 2800 rpms on a long grade? everytime the temps started to rise, I backed out to around 2000 to 2200 rpms.

I let mine rev and it seems to help. I keep an eagle eye on it though. When my fan kicks in it cools down. I have also been told(on here) that the factory gauge lies. I can not verify this, though.

Pull you CAC and radiator and clean out the fins. That should help. Over time they get full of all kinds of crap.

Excuse my ignorance, but what is the CAC?

Mine never gets hot pulling 25K-30K but my EGTs are insane. Let me know how the W/M injection helps.

Only time mine got hot was before the motor onloaded a lot of coolant. My intercooler and radiator must have been full of crap cause once I cleaned them and installed a new motor things were fine.

I know the transmission will heat up if the engine is turning high rpm for an extended period of time because the fluid is passing through the cooler so quickly but it sounds like your radiator might be obstructed like mentioned above. The engine temp shouldn't move much even in that heat.

The CAC is the Charge Air Cooler for the turbo.

Basically you need to disassemble the whole "stack" and clean everything. The tranny cooler, the ac condenser, the CAC, and the radiator. This would be a great place to start and IMHO should part of your annual spring cleaning.:)

I agree on cleaning the stack.

I would also think going faster would make it run cooler the fan would be moving more air and the additional air would be pushed through the radiator

The faster you go, the more aerodynamic drag there is. The faster you go the more fuel per second you are burning. The increase in air speed to the rad is far less then the increase in fuel burned, so the temps go up.

So you take apart the "stack", all the coolers on the front, tranny cooler, intercooler, ac condensor, and the radiator. When you do this, do you have to do anything with the AC lines, evacuate the system, take the lines off, and then have the AC system recharged?

I leave the ac condenser hanging there and hooked up. Normally we also leave the tranny cooler and just spin it out of the way. The CAC and the Rad we take completely out.

http://www.dieselplace.com/forum/attachment.php?attachmentid=25056&d=1157985997

Have you guys found a "better" way of cleaning the stack? I usually take them out and spray them off with the hose from the back to the front.

you should look into an aftermarket trans cooler. Mike L has a real nice one. i know the hills you are talking about and have pulled heavy loads up them myself. can you tell if your engine fan is kicking on? i know my engine will start to heat up then will cool back down once the fan kicks on. the trans is hard to cool down though. i would look at the trans cooler if you are going to be doing alot of heavy pulling.

I have an 02, see my sig. I have 120,000 miles on the truck currently.

I tow a 17-18,000pd 5er all the time and temps are fine. It hits 210 on engine and the fan kicks on. I had an edge and ran on 5, w/built trans, and used the attitude and temps were the same. Even with trans built I only would hit 210 on trans temp.

I have run it on lv9 ppe 330 hp and the temps are still the same. I can hold 55 on almost all hills and I really only drive by the egts.

Have you every flushed the radiator? When was the last time you flushed the trans?

I must be one of the lucky ones with no overheating issues. I would still flush trans and radiator.

I too drive the 17 on occassion and I can understand how your temps would be climbing. Take the truck to a pressure washer drive through car wash and blow out your radiator.

Only time my trans got hot was in similar temps up the 13 mile long Baker grade on the 15 towards Vegas. I was 18,800 total weight at the time and I had to back down to 55mph up the grade to maintain trans temp (it threw the first warning on dash display). Haven't towed in similar conditions again. My truck was pretty new at the time (but past the no-tow break in mileage by a long ways).

I've been the same problem I think. My edge box is reading different from the truck. I've had it as hot as 225 and the truck still reads the same. The fan clutch works fine but seems to have a mind of its own! It runs a lot. and always runs at different temps never always the same sequence. Its killing my fuel millage!

Cleaning with a pressure washer with the stack still installed doesn't cut it. Been there and done that:mad:. You must pull the stack apart to clean it.
Dexter

what i find is i push mine close to the gov the temp starts to climb

Try to clean your stack and try pulling the hill again. Remember most of the people on this site have no idea what the grades are between Phx and Flagstaff on I-17. My 03 Dmax with small tune pulls my 13,000 TT WW up the hills without any issues if I stay below 2600 RPM, any faster RPM than that the temps start to creep up. Another thing to watch is the head or tail wind when pulling. I have seen very high temps pulling up Black Canyon with a huge tail wind because I couldn't go fast enough to get the air through the rad. I had to stop at Sunset point and let it cool off.

Try it again and see before you start changing anything major.