Cummins 5.9 24V - What's a normal running temp?

[Bluthebus00]

Hey guys,

We've been loving our rig and are going on at least one trip every month.
With the summer's ambient temps hovering around 80-90F, the coolant temps now hover just under 220F. The clutched engine fan does kick in every once in a while keeping temps out of the 220s. This is at highway speeds holding 55-60mph.

We have a 2000 Cummins 5.9L ISB 24V mated to an Allison AT545(no surprises there, I know). The rig has a 26' transit/shuttle chassis. Weight-wise, we're at exactly 20,000lbs gross(including the finished conversion, passengers, a full tank of diesel, all of our stuff for the trip, and fresh water onboard)


Thoughts / Recommendations?

[Mr4btTahoe]

220 is warm but still safe. I'd probably give back flushing the radiator a shot. What I mean is use a pressure washer from the inside of the radiator (fan shroud side) to blow all the dirt, bugs, etc out of the front that have collected. Also check the coolant and make sure it's clean. May consider a change if it's been a while.

[ewo1]

Originally Posted by Mr4btTahoe

220 is warm but still safe. I'd probably give back flushing the radiator a shot. What I mean is use a pressure washer from the inside of the radiator (fan shroud side) to blow all the dirt, bugs, etc out of the front that have collected. Also check the coolant and make sure it's clean. May consider a change if it's been a while.

Cleaning the radiator is very good advice.
If you can't get the pressure washer wand in behind the radiator you might also consider using a/c coil cleaner and a garden hose. That too will accomplish the job!

[Booyah45828]

What rpm are you at while doing this? Trans shifting fine with no slippage?

It's warm, but with 90 degree exterior temps, an at545, and an engine running against the governor, it might be normal.

[aridgedell]

Mine runs right about there too. Thats after new radiator, water pump, thermostat and belt. Im pretty sure the guages are a little off because when hooked up to a computer the ecm doesnt show history temps that high.

[Ourversionoflife3]

We have the same engine, but an Allison 2500 transmission. Our bus ran warm when when we first bought it. At one point on the drive home from picking it up the gauge showed 235… but mostly hung out at 210-215. We did a radiator flush, new water pump, and new thermostat. The thermostat was the key! The school was using the correct one for a Dodge Ram, but not adequate for a bus! The replacement thermostat was way bigger, I assume allowing more of a coolant flow.

We also bought a scan gauge. The dash gauge still shows about 200 during cruise, but the scan gauge usually shows around 186, which is right in the middle of the 180-190 that Cummins says it should be. It’s quite possible your stock gauge is not accurate. Seeing the real number on the scan gauge gave me a lot of peace of mind that we never actually hit 235, probably hit 220 max.

Booyah hooked us up with the part number for the proper thermostat.