I'm seeing ECT reach no more than 196 degrees during highway driving. They usually sit closer to 188-192. During that time, EOT is generally 200-205. The only time my ECT nears the temps of EOT is sitting still at a light.

My concern is that the delta is usually at or near the 15 degree mark. What I'm trying to determine is exactly what's keeping the ECT so low.

I've owned truck since 163k miles. Just turned over 200k. Almost immediately, I had the oil cooler and EGR replaced with a Alliant (original EGR developed a leak, needed a quick repair). On a coolant related note, I've also installed a new Thermostat, Dieselsite coolant filter and replaced the heater Core.

I've read that cool spots can originate from a blockage. Could it also be from a faulty water pump? I'm using 50% FinalCharge ELC coolant and 50% distilled water. Have never had a coolant flush performed.

Thoughts?

 

Off hand your numbers don't look that bad. The only time the 15 degree spread comes into play is at 60 to 65 mph steady speed on flat ground with the engine totally heat saturated. That's app. 15 to 20 miles of high way driving. When doing hills up or down or cresting the ect/eot's will always be chasing each other and sometimes with dramatic spreads.

 

So now that it's warming up, I had a chance the past couple days to commute on hour long trips doing about a steady 70mph. During those trips (somewhat hilly since we're in Kentucky), EOT reached 218 while ECT remained in the high 190s. It seems the only time my ECTs exceed 200 degrees is when stopped or nearly stopped.

I've thought this through a couple times, but haven't yet come to a conclusion as to where I should begin checking. My biggest questions are:

1) Why is my coolant staying so cool when running, while the oil continues to get warmer. Blockage or is it really circulating so well that it remains cool?

2) Why when I slow or come to a stop does the coolant temp elevate, when it seems it should be elevated for the majority of the time the oil is at a higher temperature. It's almost like the coolant isn't flowing through the hotter parts of the engine except for when at idle speeds. Is there a specific type of blockage that would cause this behavior?

 

If your using a stock Thermost (I don't see where you said you replaced with the mishimoto if you did let us know) they are 192° so your coolant being 188°-192° is right where you should be. The only reason other guys are seeing 198°-204° is they have a 200° t-stat. Also from your post it sounds like you replaced both the egr and oil cooler with alliant pieces it may just be due to the design of the allaint oil cooler that your seeing a little higher oil temps. It wouldn't be the first aftermarket cooler that wasn't as efficient as the factory unit.

 

Wrong. My 2005 ran 196 to 204 the entire ten years that I had her with the stock t-stat. I'm not saying that all of them did, but his ect's are not out of the realm of a stock t-stat.

 

The 6.0 thermostat is designed to fail open if the thermostat is even partially open it is not retaining collant in the engine long enough to absorb the necessary amount of heat it is supposed to absorb. This will keep your overall coolant temps lower than normal.

This is a complex heat exchange system and all parts have to work correctly together to accomplish their job.

This may be your issue.

 

I never said his temps were out of the realm of the stock t-stat the O.P. Was the one questioning his temps of 188°-192° being low I said his ect was right where it should be with the stock t-stat. I guess what I should have said is where you see guys on here talking about their 198°-204° ect is because they switched to the 200° mishimoto t-stat since that is a hot topic lately cause I don't see many people saying their truck is running that warm with the stock t-stat unless they're towing. In fact your the first I've heard anyone running that warm on the stock t-stat that's why they're switching to the 200° T-stat. I don't think I gave any bad or wrong info. Your truck sounds like it was the exception not the norm not that it was a bad thing.

 

I'd still have that truck if I could keep her in turbos. That was her achilles heal.

 

What do you suspect to be the cause of your turbo issues.
I have noticed over the years that some trucks just eat turbos like candy and others do not.
Many times I have not seen any glareing differences between these trucks and yet some oeat turbos and some do not.

I guess that is the $64,000 guestion. LOL

 

Roughly every 20,000 miles. Baffled the techs. The last one they said everything was in spec. installed a new center sectin, vgt and egr valve and it still wouldn't work. They had to install a new turbo.

 

Pretty much matches our findings in the fleet also. No real discernable reason why they just did.

 

I'm hoping the turbo on my 2015 lasts a lot longer. I will say the 2005 never left me stranded and was otherwise a great truck.

 

I am going to differ a little from all you all. I say you have three things going on, atleast to some ip extent. 1. You are running 50/50 pre mix ELC with straight deionized water. That means your ELC end % is roughly 25%. This is not enough to protect you in higher temps and towing or lower temps, and will affect the properties of heat dissipation. 2. You may have a thermostat going bad, could be stuck open. It might be intermittent. I know you said this has been changed recently, but I would look at changeling it. Water boils at 212 degrees, take it out and test it, use a thermometer in water and see when it starts to close. 3. Your Alliant oil cooler, how big is it, does it have a smaller surface area to coolant, larger tubes? This is likely creating less oil cooling so like is previously stated all three factors are messing with your delta. Only way to really know is address each issue one at a time. The only other thing is the water pump, restricted flow to the cooler from water pump, kinked pipe?