I have a 2011 f350 with the 6.2l gas. The problem I am having is the truck blows cold air at an idle. I installed a greaser in the back that you tap into the heater hoses to circulate hot water thru to keep the grease flowing in the cold temps. If I rev the engine up just a little i.e. 1000rpm or so, It has nice hot air. I have bled this and really run the heck out of it trying to make sure its not air bound. There is a restricter in one of the heater hoses from the factory. Im wondering if I should pull this out? any thoughts on this problem?

 

How about moving the grease heater plumbing to the return line out of the heater core? It sounds like it is currently in the input line.

 

Well I have been doing some further testing. I did move the line to both the input and output of the heater core. I also took out the restrictor and put a clear piece of hose so I could actually see what was happpening. I found that when the engine is idling there is practically no flow thru the hoses. Im guessing that it just doesnt have enough omph to push the water?

 

That could be.... water pump flow is rpm dependent. Surprising it is that low, but if it is, it is.

 

Well I actually stuck A flow meter in the hose to see what the actual numbers were..The stock setup it flows 9 gpm at 3000 rpm and less than 1 gpm at idle. I hooked up the grease unit and got 7gpm at 3000rpm and nothing at idle. So I guess there is just to much restriction to be able to do this. So now Im going to try a 12 volt pump and see how that works....The other interesting thing about this is I have done this on a ton of older fords i.e. 2010 and back..never had this problem!..other chevy brands too. Its almost like they detuned the water pump or something..

 

The minimal flow at idle from main water pump is normal.
Because of that all Mercedes cars in last 40 years are equipped with auxiliary water pump that circulate coolant via heater core regardless the engine speed.
I had that pump fail on my car one time and I could feel colder air at stop lights even in 50F winter.
If that bugs you so much, why don't you add this pump to your truck? With some extra wiring you can run the pump and blower with engine off -using engine heat for cabin comfort for about 1/2 hr after engine shut down.

 

I think your on the right track with the electric water pump, I work on Limousines for a living and we use these to improve rear heat performance, they work great.

 

Moved to the 6.2L V8 forum.