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Old 07-31-2019, 01:20 PM   #1
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Is high engine temps inherent in Cat C7?

Cruising along in 108 temperatures, in desert, engine heat about midway between low and hot. Climb a grade, with toad attached, and temps approach redline, with info center light on saying 220 degrees.

Freightliner 2004 chassis, with a 2005 coach build date. Cat C7, 350 hp, with rear radiator. Serviced belts, hoses, radiator, cac and other items checked before trip.

Am I asking too much of the coach for the heat conditions, or should I suspect something else?

When running up grades I keep rpms between 2200-2400.
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Old 07-31-2019, 01:43 PM   #2
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I have the same engine and the same configuration (rear radiator). Our temps run in the same range as yours however, my radiator and inter-cooler need cleaning. My overheat problems are resultant of the engines "slobber tube" being positioned in the wrong place. See the video I am attaching here.

I am not saying that's your problem but it's worth looking into. In my case, I have opted to have the radiators cleaned professionally as I cannot get the fan shroud loose to clean them. I did put a catch container on the end of my slobber tube to prevent oil from getting circulated up into the radiators. Hope this helps a bit.
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Old 07-31-2019, 08:08 PM   #3
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high engine temps

i had the same problem on my old mh, cat engine. one way to check to see if the radiator needs cleaning is to get under the coach and reach your arm up between the fan blades and rub your hand on the radiator. if your hand is full of oil you need to clean the radiator. i took my mh to a repair shop that works on trucks. i do not know what kind of cleaner they used but after they cleaned it ever thing was good, under $200.00. not the $5000.00 they charge when they remove the radiator. hope this helps edit: i extended the slobber tube past the radiator. make sure the tube does not have any highs or lows so the oil does not get trapped. good luck harland
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Old 07-31-2019, 09:01 PM   #4
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Hello all, If your slobber tube was in the wrong place before 2005 I think your radiator is most likely very dirty take a look at my project.

C7 Radiator/CAC Removal And Deep Maintenance


My tube was below and to the rear of the radiator (2006) so it was not that dirty but a friend of mine had the tube in front of his radiator(2004) and his was very oily and dirty.

My engine runs at 183/188 deg never more we dont have many grades in the east but it will run 183 when outside air temp is 100

Thanks, Joe
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Old 07-31-2019, 11:59 PM   #5
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Quote:
Originally Posted by Just BK View Post
Cruising along in 108 temperatures, in desert, engine heat about midway between low and hot. Climb a grade, with toad attached, and temps approach redline, with info center light on saying 220 degrees.

Freightliner 2004 chassis, with a 2005 coach build date. Cat C7, 350 hp, with rear radiator. Serviced belts, hoses, radiator, cac and other items checked before trip.

Am I asking too much of the coach for the heat conditions, or should I suspect something else?

When running up grades I keep rpms between 2200-2400.
No you shouldn't be getting that hot. Ran my C7 in 38 ft rv for 5 years in Az Tucson and Phoenix. Yuma. I never got over 208. As said radiator and after cooler external plugging is the normal cause. Loose Water pump belt is the next most common. Temperature regulators, fan belt, radiator cap not sealing, and antifreeze level too high. Hope that helps. Safe Travels
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Old 08-01-2019, 07:21 AM   #6
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Quote:
Originally Posted by Cat View Post
No you shouldn't be getting that hot. Ran my C7 in 38 ft rv for 5 years in Az Tucson and Phoenix. Yuma. I never got over 208. As said radiator and after cooler external plugging is the normal cause. Loose Water pump belt is the next most common. Temperature regulators, fan belt, radiator cap not sealing, and antifreeze level too high. Hope that helps. Safe Travels
Just for my information; I'm curious about the antifreeze comment. Could you expand on this a little?
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Old 08-01-2019, 07:38 AM   #7
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Quote:
Originally Posted by Just BK View Post
Cruising along in 108 temperatures, in desert, engine heat about midway between low and hot. Climb a grade, with toad attached, and temps approach redline, with info center light on saying 220 degrees.

Freightliner 2004 chassis, with a 2005 coach build date. Cat C7, 350 hp, with rear radiator. Serviced belts, hoses, radiator, cac and other items checked before trip.

Am I asking too much of the coach for the heat conditions, or should I suspect something else?

When running up grades I keep rpms between 2200-2400.
As you probably already read, your engine temperatures are not normal. My Cat C7 fluxuates between 185 and 195 and never gets over 195 according to the Medallion Information display. In my opinion, exterior dirty radiators would be #1 cause. Cat mentioned regulators. There are two engine thermostats that Cat calls regulators. One or both could be failing. I think Cat recommends changing them out every so often.

I have a radiator cleaning instructions if you want them.
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Old 08-01-2019, 12:15 PM   #8
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Just for my information; I'm curious about the antifreeze comment. Could you expand on this a little?
At a 50-50 antifreeze mix you lose about 2-4 degrees ambient cooling offcapability. That not a big deal and the cooling systems are designed for that loss. But as the concentration goes up you start losing dramatically more cooling.capability. 60 % antifreeze is pretty significant loss very difficult to stay cool under load ,70%and above no way.
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Old 08-01-2019, 02:31 PM   #9
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The only time my C7 temp exceeded 200 was when I was a gal low on 50/50 after I had the system flushed.

My manual says to clean the radiator annually. I'm having Cat do my engine service this year and will have them change serpentine belt, Ck tensioner and water pump. Asking them to inspect hoses and back side of radiator too.

I'll be climbing under and doing the hand rub to check it out. Doubt if I have any oil on it. The only time I had oil coming from my slobber tube was after FL put 24 qts of oil in a 19 qt engine - Tech said he didn't realize I had the shallow pan.

Let us know how you come out as we all continue to learn.

Drive safe - Richard
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Old 08-01-2019, 03:03 PM   #10
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I talked with local RV shop. Said bring in and will check fan clutch, steam clean radiator/CAC, if needed, and check slobber tube location. Belts inspected prior to my trip but will verify condition and tightness.
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Old 08-01-2019, 05:15 PM   #11
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When inspecting the CAC and the radiator you can only see one side of each. They are sandwiched together with about 2 inches of space between them. The only way to actually see between them is to cut a hole in the fan shroud and even then it is a crap shoot if you can see. Here is a picture of the hidden side of the radiator after another owner actually removed the radiator for inspection. He thought he was doing a good job cleaning them too!
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Old 08-01-2019, 08:56 PM   #12
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I lived my Cat C7 in my previous rig. It’s sound was unbeatable, but it was quite predictable with its engineering flaws. Marked it up to character...
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Old 08-02-2019, 02:14 AM   #13
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Is high engine temps inherent in Cat C7?

I have a 3126B, 330hp, in my Ď02 Dutch Star. Similar to your C7, but I donít know the substantive differences. Last summer (2018- very hot), I battled overheating from central TX up to WY at a couple of different FL chassis shops. My normal 195 would be ok on flat ground, but if I started to pull any kind of grade temp would climb well over 210&. Rads were cleaned, belts checked and set, etc. No help.
Finally, went to Wyoming Machinery, a CAT center near Cheyenne. They drained, chem flushed, refilled the whole system with new Cat ELC; replaced both thermostats. Prob solved. Turns out my old. Coolant was seven years old on a 5 year lifespan. Other techs had told me as long as the coolant strips checked ok I was good. Apparently not.
One thing I found in all my research then was this: apparently, there is a noted percentage of 3126 engines that exhibit overheat probs when operating at elevations over about 3500 ft. I had never had probs of this kind before, but I thought Iíd mention it. I donít know how or if this might relate to the C7.
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Old 08-02-2019, 12:47 PM   #14
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It was 108 degrees in Baker, CA according to their big thermometer with the coach’s temp indicating 112 (pavement heat reflection?). For those who have gone this way, towards Vegas, there is a sign...”uphill grade next 16 miles, turn off air conditioning”. Not only did that, but turned on heater, which initially gave a noticeable drop in engine temps but slowly recovered to near redline. Now hot outside, heater going full throttle, things are getting toasty in coach...needless to say. Traveling about 35 mph in truck lane engine rpm 2200-2400.

Second line of defense, fire up the Onan and turn on both 15k AC units including ceiling fan in rear bedroom. Some relief up front but the mid coach back was nice. Was thinking about those long fire engines with another steering in the back.

Never got an engine warning light, just info center stating 220 degrees, with accompanying check info center light on instrument panel.

Don’t want to do this again, so having it checked per my previous post.
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