I back flushed my entire cooling system yesterday,and today I am flushing the tap water out with distilled water and i have ran into a issue.After draining the water from the radiator and the drivers side of the block,i add about 3-1/2 to 4 gallons of distilled water in,i squeeze the upper radiator hose to help purge the system.But for some reason it seems that the hot water is not getting to the radiator,I drove the truck 13miles to get the water hot so i can drain it,and i noticed this when the lower radiator hose was dripping water. Whats dripping out of the lower radiator hose is cool water,also my degas(over flow) tank is now developing pressure that i never noticed before(i have never tried to open it either while its hot until now) I also did a ipr coolant filter while i was at it,i have 1 line hooked(the filter comes with a plastic T) up to the passenger side metal tube(before the actuator for heater core) and the other hose i have running off the return line under the degas tank.Truck is a 07 and has 19,821 miles if that matters.

Also,going by my aeroforce guage,it says the coolant temp will fluctuate between 186-194,so the thermostat is working i assume(which i also replaced,so its brand new,like 13 miles on it) and my oil temp stays between 184-187. The stock dummy coolant temp needle stays right in the center.

heat controls were set on full blast so i could get the distilled water in the heater core,i rolled down the passenger window and closed my vents to keep from cooking to death while driving,the heat diffinately works lol..

Now i just drained,and refilled the whole system(except for the 2-3 gallons i cant get out of the block),this time to make sure there was little to no air trapped in the radiator,i filled the radiator first with a funnel and a piece of heater hose,until distilled water poured out of the upper outlet. I filled the upper hose and connected the 2,proceeded to fill it up through the degas tank,started up the truck and its doing it again. The hoses get real hard and I relieve the pressure out of the system by slowly loosening the degas tank lid. The top of the radiator is 127F+ the lower is 87F,and in case anyone was wondering its 67F outside.Is this normal?

I have flushed the coolant system in a ranger i use to have,and in my lightning without problems,this diesel has me stumped...Sorry for the long post but the other forums are as useless as a retrieval dog with no legs.

 

What brand thermostat did you use? Only motorcraft should be used in these trucks aftermarket ones have been known to cause issues.

 

the thermostat is a oem motorcraft,i replaced the housing and all since it was only like $21.

 

i apologise if posting a link to a different forum or whatever is against the rules,but going by this picture of the 6.0L "bible"....the thermostat lets water out of the engine instead of the normal in? the picture shows cool water going from the bottom hose and warm coming from the top? or am i just on drugs? Page 17: Cooling System

 

I'm not very familiar with the 6.0, but the trick with my 7.3 was that you had to add the coolant VERY VERY slowly, otherwise it would airlock, and you couldn't get all the coolant in.

I think if you drain the rad, take out the freeze plugs, drain the block, and try again, but add reaaaaly realy slow, it could work.

 

hmm...ill try it,i just added another distilled water flush in the system and im gonna run to a couple local stores.

 

Alright...wtf...i clamped off the "outlet" hose from the coolant filter(goes to the return hose under degas tank) and everything works as it should...the lower radiator hose gets warm to the touch,the water coming out of the radiater from the drain is 120ish deg,where as before it was as cool as the water i poured in..whats going on here?

 

Sounds like maybe you had a major air bubble that worked itself out of the system.

 

only thing i did different though was clamp off the outlet hose from the coolant filter,and this is the 4th flush or so,got enough distilled water here for another flush,then gonna go to the store and buy 8 or so more gallons.