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2007 KW with ISX runs hot

Over the last few weeks I've noticed my water temp running about 10 degrees hotter than normal. It usually stays between 180 and 190, now it's staying between 190 and 200 thus the slightest pull or anytime I have to get into the throttle the fan kicks on. I've replaced the radiator less than a year ago. Also I've have to add a gallon of antifreeze every two or three weeks, but it does have a small leak close to the egr. I haven't any real mpg loss, still averaging 6.4 over the last month. I've been an O/O for the past 15 years and never had an issue with the fan on so much, any suggestions of where I should start looking ?

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I sent in a reply two days ago but I don't think it posted, anyway Tuesday morning I woke up and decided to unplug the egr. The truck ran really hot Monday, it was 100 degrees out and my fan stayed on constantly, my water temperatue stayed between 200 -210, even when I was empty. Tuesday complete different story, same weather, again it was 100 degrees out all day, I was loaded with 46000 and the truck ran like it should , my fan only came on once durring a steep pull, and water temp stayed about 190. So I'm not sure what in the egr system was causing this problem but I'm going to get it into my mechanic, so he can check it out.

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it could be bad thermostats or a leaking egr cooler.

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Well I thought about changing the thermostats because I'm sure they're original with 748875 miles so I'll start there but I replaced the egr cooler just over a year ago and didn't know it could leak

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cummins shops can pressure test those - the leak is internal and iirc the coolant is burned off in the cylinders.

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You should have only 1 thermostat on that ISX

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1 for engine and 1 for oil cooler.

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I guess I should have phased that differently on the 1 thermostat

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Your still good on your water temp, will actually run more efficient at the hotter temp but it would be good to find out why your temp is running hotter. If you are losing coolant at the EGR then the amount might be the difference. when you re-fill the cooling system does it run cooler till the coolant level goes down?

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I've always had to add coolant to this truck and my last ISX i owned needed coolant every few weeks also, and the truck still runs hot even after adding coolant

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Have you cleaned out the bugs and dirt in radiator and charge air cooler I use to have a Detroit series 60 like clock work once year or I would develop the same problem your having and I even ran screens. I now have Cummins ISX with def and the coolant temp is just like yours was before the started climbing. My coolant temp is 185

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There's not a lot of dirt and bugs clogging the radiator but I will get it blown out to see if it makes a difference

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Check back and let us know what the problem was would you R Gaskin

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I had my radiator repaired about a year ago and was told it would need replacing in future, so I am keeping eye on it. Truck seemed to run a LITTLE hotter this summer, so I thought was just radiator going downhill. I have been running 50/50 coolant mix since radiator repair. or, so I thought.

I had my coolant tested this week at CMC and results came back 68% coolant. Not sure how that happened, looked back at all of my coolant purchase/repair receipts, can not find any cause. I thought I may have bought some 100% coolant by mistake, but could did not see any evidence of that.

Lab suggests drain out 10% and refill with "manufacturer approved water" (does that mean distilled?) and sample again in 90 days. Not sure this applies to your situation, but wanted to pass it on.

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Yes I've been told to use distilled water also, I've used a 50/50 extended life mix and have used regular water in the past, but now that I know what to add I just stick to the pre diluted mix and stay away from water, the trucks been running so much better after unplugging the Egr, but I still want to find the source of the problem

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R Gaskin will be eternally grateful.
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