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Have 2007 Holiday Rambler Endeavor with 400 HP Cummins ISL with 88,000 miles, original owner. Started experiencing overheating issues on return trip from Pacific Northwest while outside temps were 103 to 105. Started seeing engine temps running in 220 range on even moderated grades but only at 224 did check engine light come on till cresting grade however in the 205 to 208 degree range i started experiencing engine derating or loss of power on grades. As I had filled up with biodiesel for first time on Washington State, thought may have fuel filter issue so had them changed in Utah. Problem persisted but i limpen back to WV and immediately went to local Cummins Engine Service Center. Diagnostic codes only showing overheating issue but had cooling system checked out and flushed, new fuel filters again, fan checked out, water pump and t'stat replaced, and a sensor that is tied into engine derating replaced. Derating problem continues. engine preforms great on level grades and generally temps do not get extreme until heavy grades. On even moderate grades the stop engine light is coming on at anywhere from 197 to 210 and a significant loss of power starts to occur on moderate grades. on one extreme grade i did have engine temps exceed 224 and Check engine light came on as temps went to 228 before cresting hill. pull the hill only maintaining 25 miles per hour. again limped home home ant took it to Cummins. they seem to be at a loss. I question EGR but their diagnosis seems to point to no issue. Anyone else experience similar issues or have thoughts to point me in a direction.

I have a 2001 American Eagle 40 foot with a Cummins 350 that weights 33k. I tow a Grand Cherokee that weighs 8k. I am told that I need and estimated 10 horse for every 10k of weight so I am somewhat under powered. I have had my radiator fins pressure cleaned, the cooling system flushed and pressure tested and the fans tested to make sure they are kicking on and running at the appropriate time/temp. Additionally I have changed out the thermostat to make sure it is not sticking or causing flow issues. On hill climbs in Colorado, Arizona and Nevada I will constantly overheat and have to pull over to cool. I use the Alison mode to run between 2200 and 2400rpm during climbs to increase circulation but eventually my alarm kicks off. I never heat to critical levels but alarms start at about 190 or 200, normal running temp for this coach is 160-170. My temp gauge goes up to 240 but I never heat more than 200-210 but I don't like running that hot and the alarm is distracting. Besides the climbs, I saw last week this heating on flats in Nevada. Of course the outside temp was 100 but I would not have expected overheating on flats. Now in the fall and winter months most climbs and all flats don't cause overheating due to the cooler air. The engine is well kept, has about 75k on it and fluid and filters are constantly maintained. Now what is very strange is that I lose about 1/3 gallon of coolant every 400-500 miles. It does not drip out as I have zero leaks under the coach. It is not making it's way into the engine as engine fluids show absolutely no signs of moisture. I have had the system pressure tested 3 times to make sure I don't have a high temp hiss/steam leak and the reservoir tubes and cap are not leaking. My questions are as follows. 1. Does this just sound like a HP issue and that the 350 just can't handle the 41k pounds of coach and toad? 2. Any ideas where the coolant may be going? Some have suggested it may be leaking into the turbo but that makes no sense to me 3. Does anyone know of an after market turbo monitor gauge so I can monitor that with RPM? 4. Are there any after market cooling systems that can be put on to help with the overheating or do I just need to buy a new coach with a larger engine? Thanks for reading!

I have a 2009 Forest River Berkshire Class A diesel pusher with a 6.7L Cummins that keeps overheating. In the past month I have: First, Had the rear radiator blown out with air and then pressure washed. Lots of black filthy water came out. Still overheating. Then: 1. Had the Turbo replaced ($3400 rebuilt part-if you get one BE SURE it comes with the actuator) and the exhaust fixed where it had come loose and had it re-milled to fit better. $2800 labor. The tech showed me the turbo and it was definitely jammed up and not able to spin freely. Drove away, still overheating. Returned and then: 2. Had thermostat replaced $551 Drove away, still overheating, took it back third time and then: 3. Had a re-gen done on the catalytic converter 4. Replaced the air filter - it was filthy and jammed up with dirt Did all that at a place called Ross Point Truck Repair in Post Falls, ID. Drove away, still overheating. SPENT 4 WEEKS THERE!!! STILL NOT FIXED!!! 5. Had the inner cooler or CAC sprayed out with water Took it to Western States in Spokane WA and they hooked it to the computer and said it was not showing any codes. If I downshift all the way to 3rd, 2nd or 1st on my Allison transmission, and get the RPM's up to like 2700-3000, it still gets hot but doesn't overheat. Of course, I can only go like 30-45mph. Doing lots of mountain driving in the next week. My wife and I travel for work, so if we are stuck somewhere not moving we are losing lots of money. A few folks have suggested the water pump. Another guy said maybe it's a sensor, but it mainly overheats on big hills. ALTHOUGH, it has overheated on flat ground towing the car about 15 minutes in to the trip. Our manufacturer says we should only tow 5000 lbs, our car is 6000, every mechanic I have talked to says the Cummins 6.7L should tow 10,000 lbs with no issues. We have had this rig since Oct 2017 and towed the car at least 7000 miles with no issues. It's not losing any water when it overheats. Engine oil level looks good. Transmission fluid is clear, full, and does not smell burnt. ANY IDEAS????

Fleetwood, 300 turbo, over heating. I understand clogging radiator can be a major cause and that the engine blow by down spout and spew oil into radiator to hold dirt etc. So... how to you access the radiator to clean it? Also, low coolant light on but radiator cap will turn but not pull out. Seal frozen. What cap to they take as I will have to force cap off and probably separate the seal from cap?

I thought you might benefit from this. It might save you a gob of money, in the long run. After friends sent their Discovery in for radiator service and ended up with a huge bill, I starting getting more serious about tending to mine*. Bear in mind the buddy who owned mine prior to our purchase periodically raised the closet floor and shot degreaser onto the engine and radiator, and I've done the same every six months or so in nearly two years of steady use. We had been overheating, but only under extreme conditions, eg making 2-mile constant climb at 60 mph in N. Arkansas with 100+F ambient temps (120+ against the pavement). Even then, a short downhill run with the exhaust brake on to boost rpms, or pulling over resulted in immediate return to normal. A recent trip to Galveston resulted in perfect temps, albeit with 85F outside. Still, after the trip, I applied degreaser to the aft side of the radiator, waiting 20 minutes, shot the fins with a safe blast from the hose. What looked like mouse turds showed up in the driveway. Lil' greasy mouse turds that turned into a smudge when rolled between my fingers, rather than the wholesome, nutty but slightly gritty goodness of the real thing... Clearly, the engine side of the radiator was a muffin mold of sorts for these little pellets. Using the heavy duty degreaser in a spray bottle, I hit it from the back side -- the idea was it'd pass through to the engine side -- another five or so times, waiting and rinsing each time. The next morning, I jammed a digital camera up inside the shroud and shot a series of photos. One spot on the lower right was gummed up solid, despite repeated cleaning. So, I got a gallon sprayer and loaded a 1:4 mix of the Simple Green Pro HD from Home Depot yesterday, rated safe for aluminum, sprayed the engine side of the radiator while hot, let it sit for 20 minutes and then rinsed. There was quite a difference, althought further cleaning was needed. As a result of this discovery, I'm programming a misting of degreaser up under the shroud on the engine side, after every trip. It only takes a minute or two, can be paired up with hooking up the black tank rinse, done at the same interval. Thanks for the comments below. Indeed, the moral to the story was that degreaser must always be applied to both sides of the radiator, with an emphasis on the upwind eg front side. Use good judgement to protect the delicate fins: some pressure waters have "Delicate" tips and are appropriate; if in doubt, use a hose-end sprayer.

I have an Onan Emerald 3 gen set on my 1981 Holiday Rambler. I bought it a couple months ago. I went to start onan and ended up replacing the circuit board fuel pump, and air filter. I changed the oil, filter, and spark plugs. I ran a new fuel line to tank and put a new muffler on it. I took carb off, and cleaned it. When I start it, it sounds really good, runs for about 25 minutes, and sputters for about 10 seconds and dies, with little to no load. The engine was around 280 deg.F. I noticed mice nest around engine, I cleaned alot of nests out, blew it out with air. Started again, runs for about 25 minutes, sputters and dies, still hot. Also, on dipstick, do I check oil level by screwing it in or just resting on the threads?