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Old 08-28-2012, 08:11 AM   #1
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Cummins 5.9 overheating

I have a 2004 Damon Ultrasport with a 5.9 Cummins engine. As we travel in the West, the temperature moves to the danger zone as we climb the passes. Antifreeze reserve tank is full. We shift into a lower gear and take it slow, but trucks are passing us. Any suggestions?

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Old 08-28-2012, 08:24 AM   #2
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One of the more common problems which I also experienced is the radiator and intercooler being blocked (this is the outside-air doesn't flow through). Not saying this is your problem, but something to look at.

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Old 08-28-2012, 08:28 AM   #3
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Originally Posted by jackhoyt View Post
I have a 2004 Damon Ultrasport with a 5.9 Cummins engine. As we travel in the West, the temperature moves to the danger zone as we climb the passes. Antifreeze reserve tank is full. We shift into a lower gear and take it slow, but trucks are passing us. Any suggestions?
What rpm did your engine turn up to when you shifted down ? Is your fan on the engine hydraulic or belt driven. Do you have a fan clutch ? Usually a lower gear that keeps engine rpm up to best torque/horsepower range will keep temps in range. What was OAT ? How high were the passes your crossed ? More questions than answers right now but others on this subject may have more insight.
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Old 08-28-2012, 09:11 AM   #4
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I was having same problem on latest trip, discovered the right side of the rubber shroud around the radiator helping to direct air through instead of around had torn off. Anyone know of a source to buy this to replace?

Bob & Donna
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Old 08-28-2012, 09:11 AM   #5
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As mentioned, the two primary causes are:

1. "Cool pack" (i.e., radiator, etc.) blocked with oily residue and dirt. Rear radiators are especially prone to this when the engine's crankcase vent isn't routed past the cool pack - the oily mist will accumulate on the fins of the radiator where dust will adhere and make a real mess. Just because it looks reasonably clean from the outside doesn't mean it isn't packed inside.

2. For whatever reason, the engine cooling fan isn't actuating when engine temperature climbs. The problem could be in the fan drive clutch, the fan hydraulic motor (if the fan is hydraulically driven), fan controls or engine temperature sensor.

There are other possibilities, but these are the first two items to check.

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Old 09-01-2012, 05:00 PM   #6
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Could be as simple as finding and staying at the optimum RPM. That engine peaks and likes 2000rpm. Whatever speed that gets you. Moderate climbs in 5th gear, tough climbs in 4th gear.

Let the trucks go right on by. If really hot ambient, start the genset, cool with the roof air, and shut the dash air (engine-driven) off; less heat for the engine cooling system to deal with.

Engine RPM's get the coolant moving, get the HP up, get the air moving thru the cooling pack, and thru the engine as well. Gotta remember EGT'S as well.

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