Sounds like you may be out of the woods on this. But.......did you ever check your air filter and fuel filter????

1 hour 20 minutes running with load and no change.

Sorry to say I do not know where either are located; both were supposedly checked during service at reputable dealer when I bought it in mid-April.

Oddly enough, at 1 hr 30 minutes, I turn off both a/c's and allow to run with no load - go outside to close compartment door, and return to shut off unit and temp gauge now reading almost 220. I shut the unit off.

Are you currently parked on an old Indian grave site?

Is there an aux fan for cooling that only kicks in with a load?

quote:

Sorry to say I do not know where either are located; both were supposedly checked during service at reputable dealer when I bought it in mid-April.

If they were checked recently, you are likely OK, but squirrels and mice can raise havoc anytime. The Air cleaner is easy, it is on top of the motor or very close by and is attached to the intake. The fuel filter may be anywhere between the fuel solenoid and the fuel tank. If you're lucky, it has a glass or plastic see through bottom for looking at the condition of the fuel.

Buy some "Engine Gunk Cleaner" (actual name of product) and read the can - you need to spray it on a hot engine. Engine fluids and dirt need to be cleaned off of the engine to allow it to run cooler. Gently spray any areas around the radiator to get the dirt off - you will blow a radiator apart if you spray too much water psi on the fins.

Exhaust restriction is another concern. Because your engine runs at a constant speed, this is a little harder to detect if the restriction doesn't cause lower engine rpm's. Look around to make sure the exhaust pipe isn't bent partially closed.

Even though you see the fanbelt still on there - have you tried to turn it and see if the belt is loose? A slipping belt is something that you'll need to tighten up or replace if it's glazed. Things expand when you get them hot so if it slips when it's cool - it'll slip more when it's hot.

Let's start with some of this stuff first - forget the fact that the Cummins Dealer has already checked this for you - your coach is 21 years old - things wear out and things come loose - mechanics make mistakes - we are dealing with the reality as we have it now.

Ran 5 1/2 hours today with load - two A/C's running, fan on medium to ensure that if they cycle off there is still load, plus TV. Outside temp 92 - temp gauge read 190 and just above - coach sitting still most of the time. I was working inside all day and needed some A/C - I did remove load at the end of the day and let gennie run with no load for about 5 minutes and saw the temp gauge move up slightly but did not have time to let it go any longer and was not interested in letting it overheat for the sake of overheating. No unusual bends in exhaust pipe, no gunk build up on engine - in fact way cleaner the Cummins. Checked fins on radiator and no obvious bocklages or damage - rinsed with low pressure hose.

had all kinds of problems added aux fan off a car elimated my over heating problems

1) And the belt... Did you manually check the belt for slippage?

2) Check your antifreeze protection. People sometimes only add antifreeze to a system. This over addition of coolant cause the antifreeze protection to be too much - this inhibits proper heat transfer. You need coolant and water mixed at about 50-50. Heck, if it's been a few years I would probably just flush the coolant system, replace the radiator cap and start new.

3) When it does start to overheat, visually inspect the upper and lower radiator hoses to make sure one isn't sucking itself shut. Some hoses require a spring coil insert that prevents this from happening. Yours might be missing, or maybe the hose has lost its ability to keep its form.

4) Do we know if your fan is a puller or pusher type of fan? Some mechanics have been know to reinstall a fan on backwards - No Foolin

5) Is the fan inside of the shroud? - If it isn't, you'll not have the full force of the air being sucked in or pushed out that it's supposed to have.

6) Am I correct in assuming that your fan is "Direct Drive" and does not have a "Viscous Fan Clutch"? If it is a viscous, you'll need to check to make sure that style fan clutch is locking up when hot.

I give you this in the order I would start to look - insofar as what I'm having you do... this is more "light duty" in nature right now but is very important to check and do. I don't immediately make comments like - you need a thermostat or replace the waterpump. Yes, it could be these, but lets follow a logical thought process that doesn't require several hundred dollars for naught.

local shop traced the problem to either loose or bad connection for the oil pressure sending unit. My gennie radiator fan is wired to oil pressure and should start at 5 psi according to Onan. Since I found the wires disconnected, and I attempted to repair, I must have not gotten tight crimp - I did not have a crimping tool with me at the time and used pliers which is all I had. Seems to be working correctly now - time will tell. Thank you for the feedback and guidance. Race weekend and temps supposed to be in the 90's so I will definitely need it to cool off!

All's well that ends well.

Let's hope this one has ended

Hit the road with "problem solved" and generator ran great for two hours, traveling north with strong tail wind in 93-96 degree outside temp. Water temp consistently hovered around 195. After first couple of hours, temp would begin to rise to about 210-215, hover for 10 minutes or so, and then slowly drop back down to the 195. Stopped twice, fan motor still working and pulling air from outside the coach thru the radiator nicely. After a couple of hours of this the temp rose to almost 220, and after 10-15 minutes, temp did not drop, so I shut off the generator. After driving for an hour to let it cool, I pulled over to begin checking all over again and everything seemed normal. Re-started generator to check for fan motor etc, and all was fine, temp rose back to 195 and stayed for the rest of the trip. Have ran generator all night while parked at the track, a/c's working and water temp hovered below 190 all night. I seem to notice that when traveling with certain wind direction, the temp seems to run hotter than others. After stopping to check the generator, and moving on, the wind was blowing more into the passenger side of the coach, which is directly into the face of the gennie radiator. The shop mentioned they thought that if this problem persists, it may require building a little "scoop" to direct air flow more into the area. We have already trimmed away a small section of sheet metal that had deteriorated anyway near the wheel well, and made sure there are no visible obstructions to the radiator.

At this stage of the game I would use my thermal imaging gun to make sure there are no hot spots in your radiator - I would flush and refill with 50/50 mix and throw in a new T-Stat. But, my labor is free for me.