First off thanks for the wealth of information on here. I've read quite a bit, especially on injectors, and there's a lot of help on here. I'm having problems with my 2002 LB7 overheating. The first time was hauling a trailer load of straw home about a month ago. Was pulling about 18000 lbs including the trailer over sardine canyon in northern Utah. I couldn't get it to cool down even when pulled off and heat running. I replaced thermostats and fan clutch after that and on my test runs locally that seemed solve the problem. Today I went to deliver some cows to that area. No problems but I didn't push it cause I was about 16000 with trailer. The only thing I noticed was when I was doing 75 on the freeway (a/c on 93 degrees outside) it would range between 210 and 235 and would cool down to about 220 after getting up to 235. I had to come home through sardine canyon again and figured since I was empty (trailer weighs somewhere in the neighborhood of 3500 24' steel livestock trailer) I could just do 60 mph all the way up. I got almost to the top and looked down and my coolant was up to 260 and check coolant temp light came on. I pulled off turned the heat on and it cooled right down. I didn't push it over that pass once I was cooled down but the next one I tried to see what was going on. I ran it about 2200 rpm up that hill and she climbed right up. I only let it go to about 240-245 and then I dropped my speed so that I was only about 1600 rpm, turned my heat on and it cooled right down. Truck is stock except a Cat fuel filter adapter and will turn over 298,000 tomorrow. Never had this problem before even with heavier loads. It needs injectors done and a/c charged (that's the project for this week) but I don't think either of those would cause it to overheat like that, but I'm the first to admit that I don't know a everything. I'm stumped.

 

There are 3 basic reasons an engine will run hot:

1. Cooling system problem.

2. Lean fuel condition.

3. Ignition - or in this case injection - timing.

That said we must assume that it's not a timing issue, because there's no real way to alter that in a diesel without moving the injection pump.

Running lean? Not likely, If an injector is messed up it's more likely to run so rich that the exhaust is going to spew white smoke because the engine can't burn all the fuel.

But WAIT!!! Cooling system!!!
1. Go to a car wash and blow out your radiator from the inside. Dust in a radiator will wreak havoc on its ability to cool the water in it. Same with the A/C condenser!! If it's really dirty/muddy you're going to have to yank it out and spray it clean.
2. Change your thermostat. They can freeze shut, just like they can freeze open. If it's stuck partially-closed there's you problem!!
3. Squeeze both of your radiator hoses. If they're soft they can collapse when there is a draw on them, but if this happens it will most likely be the bottom hose, as that's where the water pump draws from.
4. Anti-freeze condition can contribute to a engine's inability to run cool, but not enough that you'd have a big problem with a normal street engine, but check it anyway.

 

Oops - I forgot!!! Warm up your engine, then shut it off. Grab the fan and rotate it back and forth as fast as you can. If it moves with very little resistance the fan clutch is shot.

Another way to test this is to start the engine, then get under the hood and hold your hand at near front of the engine and have someone rev it up to about 2500 rpms. If the fan doesn't blow your hand like a Class 4 tornado the fan clutch is junk.

There is a VERY good likelihood that your problem is either this, or the thermostat, but a dirty radiator can be a real headache.