Hey, this is a mish mash of symptoms that I have been able to find conditions that fit some but definately not all of them.

It started about a week ago. The first thing I noticed was my a/c was going out when I was idling. I thought that it just needed recharged, but the charge read fine. The rest of the symptoms came on yesterday afternoon. I had driven about 100 miles earlier that day with just the a/c issue, and I hooked up an empty 6x12 cargo trailer to help a friend move some furniture. When I got on the interstate with it, the truck immediately started to overheat. So I pulled over on the shoulder and turned it off. I checked coolant level and found that it was where I had left it. So I turned the truck on to move a little further off, expecting to be there a while to cool it. When I turned it on the temp immediately climbed down to normal while idling (about four seconds from redlined to the middle). I tried taking off again but about 1200 feet later it was redlined again, and check engine temp light came on. There was some belching of coolant from the degas bottle, and I lost a decent amount of coolant by the time I was done. I cycled a couple more times into a parking lot and dropped the trailer and borrowed a different truck to help the friend move and came back about four hours later. Truck was cool, and I began to take it home, about two miles away. To my suprise no overheat at all. Drove it to work tonight, with no overheat. A/C problem still persists.

In advance to someone having to ask. EGR is deleted, Oil cooler was changed about 1,000 miles ago along with thermostat. There is a coolant filter on the truck, and the rad was flushed and cleaned about 3,000 miles ago. Fan clutch engages and runs fine. No white smoke or coolant smell from the exhaust. Trailer weight was around 1,900 pounds.

I am supposed to take the truck on an 800 mile trip on friday and really would like to find out what I can fix beforehand.

Thanks in advance!

 

Thermostat stuck closed, now loosened up? You probably need to at least check the thermostat, maybe replace it if it hasn't been. can you read temps of oil, tranny, coolant, are they all the same before start up? Perhaps one of the sensors is bad, do you have access to scangauge, DashBoss, or other full gauges? I also wonder about coolant cap. When at normal temps, not overheating, can you loosen degas and is it holding pressure? What is your antifreeze percentage by hydrometer? To high water percentage can overheat and boil in the engine rather easily. Just some suggestions to get you started. Something is up, I would want to get to the bottom of things before that long trip coming up for sure.

 

Sounds as if it might be thermostat sticking shut or water pump. Impeller might be cracked.

 

Thanks all for the quick reply. I replaced the thermostat as part of regular coolant maintanance about 1,000 miles ago along with the oil cooler. I have never taken the water pump off, but I thought that would cause overheating at idle too. The coolant is a 50/50 premix, and I don't have access to any advanced gauges. Just haven't needed them yet, so I don't know the deltas or anything. Degass bottle holds pressure fine in the past and seems to be now. And I have never had it puke like that before.

 

The 50/50 premix isn't helping anything. You need the right mixture. 3.5 gallons of concentrate to 3.5 gallons of distilled water.

If you put premix in then you only have roughly 1.75 gallons of coolant and 5.25 gallons of water.

 

I will do a drain and mix it myself then. I am just suprised it could be anything that simple. I will pull the thermostat as well and heat it in some water and see when/if it opens.

 

Oh, and any suggestions on brand of concentrate to mix? I can't remember what I have been using; some mid-range 50/50 mix

 

I think you might need to install pressure gauge on the degas bottle. Hope I am wrong, but head gasket leaks can behave like you are describing.

Also, using just any-old-coolant is a bad decision. Different coolants don't mix very well with each other. If you are unsure of what is in there, you should do multiple rounds of rinses with distilled water: Drain, fill w/ distilled water, run it to circulate and mix, let it cool, repeat 5 or 6 times (there is about 2 gallons of coolant that you can't get drained out). Then add 3.5 gallons of DIESEL RATED (Cat EC1 is the common rating to look for) ELC concentrate and top off with distilled water..

 

Just want to emphasize what bismic just posted about using the appropriate type and proportion of coolant in your 6.0. Some of us (me included) here at fte have already learned that lesson the hard way. Some people like to stick with Ford Gold coolant, but like many, I have opted for the Cat EC1 rated ELC (aka Koolaid) as the coolant of choice. And realize the importance of doing multiple flushes with distilled water till you have displaced all of the current solution with distilled water before topping off with concentrated coolant for a final 50/50 mix. I think I posted a table somewhere a couple years ago of how many distilled water flushes gets you 99.something% pure distilled water.
If you haven't already, I recommend you read Coolant Change 101 as a primer.

 

The A/C "problem" tells me to focus on the fan.
It might work when 'cold' but as the PCM asks for more rpms it doesn't speed up properly.

IF your coolant temp is redline - you should hear a jet engine under the hood.
My fan has been hitting 1400 rpms in 95* days when I move from a stop light for about 1 second - and I can instantly tell my fan is working..

 

In addition to the coolant type and mixture and checking the thermostat, I think you have something else going on to overheat like that. Either the water pump impeller is shot, or the next likely is head gasket issues. It seems to happen that the impeller separates from the shaft amid then there is no pumping of coolant and the coolant super heats. On the head gasket issue, there are kits to measure for combustion products in the degas before tearing into it. It would really help to have those digital temperatures and readings from a scangauge to figure out what is going on. Good luck, here is hoping this is relatively easy, like the water pump..

 

Get an ODB2 port gauge (smart phone APP and Bluetooth adapter, or scangauge2, or any of a number of similar things - lots of threads on the dashboss too)

It'll let you see the FAN RPM, actual coolant and oil TEMP. The gauge isn't any help except to tell you "cold" or "normal" or "too hot"

 

Dirt/trash/ lots of bugs on the outside of the CAC/radiator/condensor could affect airflow. raising engine temp and interfering with a/c operation. Just a thought.

 

Is the EGR valve still installed in the intake and electrically connected?

(I don't think that is "the" problem , it could be a combination of things)

 

Thanks for all the ideas! I am sure the thermostat is good, no cold spots on the rad, and the coolant is diesel rated and all the same. I did several flushes recently. I can tell the fan is on and it all seems to be working correctly...Except I drained some oil to see if anything separated out, and sure enough, there was about 1/4" of coolant that separated out with a nasty layer in between. I now strongly suspect the head gasket of being less than good condition. The oil cooler was replaced about 1500 miles ago because I found some oil in the coolant. The guy said that he didn't find anything wrong with the head gasket, but I don't suspect he actually did an inspection of it. It was done on the dealers dime and I think it was "accidentaly" overlooked. I haven't experianced much more issue with it since the towing incident, but I think the gaskets are on their way out.

Any comments on this idea?