Have a 2005 6.0L Superduty and its running hot.

About 5 years ago I blew the EGR cooler, took out the oil cooler, replaced it, replaced the EGR valve and put in a Bullet proof diesel stainless steel EGR cooler tube. I have been down that path so am very familiar with all the delta temp requirements, plugging oil cooler, etc.

Had been running T6 Rotella in it since then, changing oil every +/-6000 km. Once it went out almost 9,000kms about 2 years back, but still, that pretty low KMS for that oil. Didn't seem to hurt anything. I change it at 6000 for the cleanliness of the oil so not to mess up injectors, or leave deposits in around the oil cooler effecting its ability to cool.

My deltas between ECT and EOT have been fantastic for the past 5 years. Always in around 7-8, and up 10-15 pulling the trailer. May hit 18 up a big hill. No issues.

Then this past summer things changed. I has to do some work to the truck and I cannot remember what I was doing, but I had to drain some of the rad fluid. Prior to this the truck ran and cooled just fine. OH, I replaced the clutch it and aftermarket clutch fan. My other one was failing at the plug and had a loose connection in the back side of the connector. The truck would over heat on the highway the odd time. I could not hear the high speed fan run. I would get out wiggle the plug, then drive again and could then hear the high speed fan come on, and it would cool right down and be ok for another day or two. Until the plug lost its connection again.

However, after I replaced the clutch fan this last summer, I closed it up and immediately went on holidays pulling my 5th wheel for a 5 hour drive. I drove for a while pulling my trailer, then I was getting some moisture platter on my windshield (on a nice sunny day no clouds) when I realized I had not tightened up my top rad hose. I pulled over and tightened it up. Had lost some fluid, so I topped it up and kept going.

The entire trip it was running hot. A lot hotter than normal. Although it was +30 C. Then climbing up a hill, a long hill, the truck went into safe mode (display said the delta was to high for too long) and i crippled it to the top of the hill at half speed or less, and sat there for over an hour while it cooled down. Just about cancelled my holidays and went back home.

Thought maybe loosing fluid had caused an air lock somehow, thought I would let it cool down and try again. So I did, wasn't going to cancel my holidays just yet... LOL

Drove for another hour as it kept heating up (235) and had to shut down and cool for another hour. The evening cooled off a bit and then we drove for another 1.5 hours to where we were going to be for the next week.

In my mind there was no way this was an airlock anymore. Let it cool off and 2 days later drove it for 2.5 hours without the trailer to another place. Then drove back to the trailer another 2.5 hours. Was running a bit warm, delta was up in the 15 range without the trailer. That was higher than normal for my truck previously. I was concerned.

Ended up buying a 2015 6.7L so parked this 6.0L and just recently started to drive it again. Was out on the highway yesterday, no trailer and its delta was up to 21-23 on the highway. It warms up really nice. Deltas are exactly even or within a degree of each other until it hits about 175

What is causing this ?

If I mixed different rad fluids would it cause this?

If I had a 50/50 water concentrate in the rad would that do it. I have been since told I should not mix more than 60/40 with distilled water, simply for the chemical protection of the rad fluid, even if the rad fluid says 50/50. Could this be contributing? However, with that said, I have been doing other work to the truck and since changed the fluid to a 60/40 mix.

Or,

Is my new clutch fan simply not working correctly ?

I have been thinking about doing a rad flush. However, my fluids are seriously clean.

Question.

If in the warm up process, the ECT and the EOT are exactly the same, or within a degree, all the ways up into the mid 170s, this would seem to tell me that my oil cooler is working correctly, and efficiently. Right or wrong ?

Then, when the engine started to heat up above what the rad and normal coolant flow cannot cool, at which time the fan is suppose to kick in, and it doesn't, the engine cannot cool itself as the fan is not working correctly ? This does not seem to make sense, as if the rad fluid is cooler by 20 degrees delta already, it should be cooling the oil. Which leads me back to the oil coiler not functioning correctly.

That starts me thinking about coolant types, blockages in the oil cooler and options for a coolant flush.

Thoughts ?

So..my thought process, keeps bringing me back to the oil cooler and some type of blockage. Maybe removing rad hoses when replacing the clutch fan broke off some build up some where that is now blocking up my oil cooler.

I am thinking of a rust de-solver coolant flush to see if that will make a difference. Seems strange that the delta temps just seems to change when I replaced the clutch fan.

What type of chemical coolant flush should I consider or not consider ? Rust de-solver ?

Saw a YOUTUBE vid on Motocraft re-de-solver, remove thermostat and a few other things, drain everything out of the drain plugs, then run the engine to 172, with the chemicals, repeat with water and then put back together.

Back flushing, vs just a engine running flush ?



Comments are greatly appreciated. Thanks

 

Is coolant even making it to 190*, if not, change the t-stat. Then test the temp spread again. Level ground at full temp for 15 minutes at around 65mph. No trailer, no hills, just flat out.

Do you have a live gauge, like a Scan Gauge II or Torque Pro app for Android and a blue tooth ELM327 OBD transmitter for the app to work.

Live gauge will help you determine actual fan speed, just to see if it's speed ramps up with higher temps.

I'd not chemical flush just yet, that will kill the oil cooler for sure. A distilled only flush would be a good option and then fill with EC-1 rated coolant, like Rotella EC1. I noticed my deltas were even less after using that coolant type, they even claim its more efficient at removing heat. Don't waste time with a back-flush either... just pull the plug, pull the block drain and flush a bunch of distilled with the t-stat removed. Fill, run the truck a few minutes, heater on high, dump it and go again. I did about 20 gallons of distilled, until it came out clear, so catch a little to see. Then just dump the block and rad one last time, refill with concentrate 3 gallons worth and top with distalled after you get all 3 gallons in. Should leave you at nearly 50/50.

See what happens from there... but I suspect the t-stat isn't right and maybe your fan isn't either.

 

Thanks, yes, it goes over 190, even into the 200s just driving down the highway with no load or trailer


Will check some of those thing tomorrow morning. Thanks

 

where is the level of coolant, just below the minimum line? Have you tried venting the cap after its warmed up? Drive until warm, then vent the de-gas very carefully to see if the level changes.

At 210*, the fan should come up in RPM and at 217*, the fan should sound like a jet engine about to take off. The temp should come down fast once the fan comes up to higher RPM. Is the EGR sensor plugged in? Have you scanned for any codes?

The EGR valve runs the fan and also does EGR control.... a bad one could possibly be hindering the fans operations, why I asked if its plugged in and no codes for it. P0401-P0407 IIRC for EGR codes, if present.

 

Could be a plugged radiator if you are overheating on the highway without a load. Have you looked down between the Intercooler & radiator? My radiator was nice and clean up top but at the bottom there were mounds of crap stuck in it. Pulled the radiator and most of the fins were jammed up with crap. Tried cleaning it, but it's just too thick to properly clean with a hose nozzle. Still ran 190 on the highway unloaded. Ended up replacing it, as it ran hot when towing (220-225 pulling long hills).

Almost sounds like a failed water pump, like you just aren't getting enough flow.

Another idea, have you checked your serpentine belt? If you were leaking coolant all over the engine you might have gotten a good amount on the belt, causing slippage, although you normally can hear that as squealing.

 

It also could be the impeller spinning on the water pump shaft.

 

Ok, pulled the EGR valve, was not bad. Cleaned it up with brake cleaner, but pretty sure that is not my issue.

Took it out on the highway with the scanner. Max temp was 183 ECT and 198 EOT.

At 177 ECT it was 197 EOT. Delta 20. No load. No trailer. Driving 124 kph, 78 mph for 20 min.

ECT did not go over 190.

Fan stayed on LOW the entire trip. Could not get the ECT up high enough for the PCM to call for a higher fan speed.

When i start it and let it warm up the delta stays pretty close all the ways up to mid 170s. When i hit the highway the delta can climb to 20-23.

Pull in off the highway and it cools down. Sit there for8-10 min idling and its back down to 172 ECT and 175 EOT.

Belt is clean no sills, tight and. Not worn. The belt is probably the original belt, but looks in pretty good shape still. I don't think it slipping.

No garbage between the rads, cleaned that all out last summer when i did the clutch fan.

Coolant levels are good. Ran with cap off, no change in elevation.


Curious about the impeller issue in the water pump, not providing enough flow.
Thinking about the water pump issue, anyway to test flow ?

 

I see operating temp for the 6.0L is 190-200

I only got to 183 ECT on last trip. If i change out my thermostat to bring up operating temp, how is that going to lower my ECT- EOT delta ?

Sorry i don't understand that.

Similar with the clutch fan. If the ECT is already well below the EOT, how would a different fan change the delta ?

It makes sense to me that either the oil cooler is partially blocked, which a fllush may or may not resolve.

Or a starting to fail water pump, might not be keeping the flow up enough at higher speeds.

Thoughts ?

 

I'd change the T Stat with a new Motorcraft and purge,then go for another ride.(your temps aren't to spec)

 

Definitely get a new thermostat as you are running too cold. Unfortunately your oil cooler is probably toast. Mine had similar numbers when I got it (ECT 180, EOT 195) and when I put in a new stat it just went up to 190/205. Worth a try and you'll need it anyways.

 

Ok, problem resolved. So this is an update. Bought a new thermostat from Ford, and also booked the truck in for a VC9 coolant flush. Ended up, that i Did not have time to change the thermostat before the appointment. So left the thermostat on the console to have them put it in when they did the flush.

Go the truck back...

Truck cools well now, truck goes over 190, deltas are all good. So happy about that.

However, maybe someone can explain something for me. It is my understanding that you need to remove the thermostat in order to flush the engine, because otherwise the T-stat is closed when cold and you cannot flush through the motor, rad and interior heater core if you do not remove the thermostat, because it is closed and blocks flow.

Due to the fact that i thought the T-stat had to come i figure it was just put the new one back in instead of putting the old one back in. So i figured i would just have Ford do that in the process.

They charged me for an hour for installing an owner supplied T-stat, $140 plus tax.

I challenged them on this, saying they had to take the other one out anyway, but they told me it was in a different process, which i think is BS. And it was extra work.

In my opinion, one of two things happened.
1) they ripped me off, or
2) they did not do a proper flush.

Still p.o'd about that, but the truck's deltas are now good.

 

It probably took more time to bring in the vehicle than r&r the t-stat yourself. I have a van and it took about and hour round trip. Tell them you are posting their rates on this forum. P