Navistar 7.3L cruise control, overheating

[jdaugh]

I just got my first bus, also my first diesel of any sort. Mostly I've had passenger cars and motorcycles in the past.

It's a 1999 Thomas mid-bus with Navistar 7.3L.
189k miles. I think it said like 9500 hours.

Drove it back from Cleveland to Detroit with gas pedal pegged, 59 mph, 2700 rpms. 85 degrees outside or so. It did fine for maybe 30 miles, then overheated. Coolant spilled from the overflow tank. I freaked out. But got back on the road and the next time it overheated, I backed off to 55 (2600 rpm). Later I had to back off to 50 (2500 rpm). I was able to go faster here and there as the sun got a little lower in the sky.

Is this normal? If not, any suggestions?

I'd also like to try and get cruise working, and maybe also remove any speed limiters, and apply any efficiency hacks if any exist. And then there's the air leak in the air dryer... (I just learned that an air dryer is a thing, ha)

Thanks for any help!

[cadillackid]

I responded in your other thread.. the cruise is likely just disabled in the ECM.. someone with the free version of servicemaxx J1708 and a nexiq or CLone can enable cruise..



if theres any factory firmware updates for the ECM then we'd have to run that through NavKal which is a subscription from navistar and it will update the ECM.. theres always some but they dont seem to do alot.. I run a 2004 ECM in my 00 T-444E and that made big imporvements in cold weather manners but of course you wont gain any speed. that in your case is gears

[jdaugh]

Lovely! Thank you.
"someone with the free version of servicemaxx J1708 and a nexiq or CLone can enable cruise"... Any tips on where to find that someone? I live in Southfield, MI.

[cadillackid]

I have a whole bunch of that navistar / tuning / scan tool software and hardware but am 4 hours away in Columbus