Hello all.new to this and hope i can get some help.i own a 2001 f150 lariat with the 5.4L triton.about 5 weeks ago i started having overheating issues.so i upgraded to a dual core rad,new water pump,T-stat,fan clutch,upper and lower hoses,and flushed the system twice.well after all this,still boiling coolant out of bottle.she had 306907k miles on her.so i went and purchased a new 5.4 long block and changed her out.now with the new engine in and about 4 hrs total time on her,shes overheating again but not boiling out of the bottle....im at a spot where im stuck and after $4500,im about fed up.
(The reason for the change was when i pulled the water pump,all the fins were gone.after all new parts and still overheating,was thinking they were in the block somewhere causing a clog)
I NEED HELP BAD....i love my truck and i need advice bad.

 

I'm not a mechanic so if someone comes along with better advice/suggestions, you may consider them over mine. My feelings won't be hurt.

1. Does it overheat at idle?
   a) If it does, let it warm up and touch the hoses, coolant crossover, etc and find out where it is cold and hot. This may help you find the problem.
   
   b) Be sure to check the water pump, listen for any noise coming from it.
2. Does it stay cool for a while then suddenly get hot?
   a) If so, you could have a hose collapsing or a sticky thermostat.
3. Can you run it without the thermostat and see how it behaves?
   a)This is to rule out thermostat, the other option for testing the thermostat is to put it in a pot of hot water and watch it open.
4. Have a radiator shop check/flush the new rad. Stranger things have happened, it could be clogged already by something that flowed in from the engine.

 

My bet is you did not get all the air out of the system.
After replacing everything, that's all that is left.
Good luck.

 

I hate to say it but, I had this same issue a couple of years ago with an Audi. The water pump grenaded and sent shrapnel all into the cooling system. I did the same as you, replaced everything coolant related. Thought I had it all fixed up but it still kept running hot, I thought I had air in the system, but coolant level never changed unless it boiled over.
After about a month of fiddling around with it........the Heater Core busted!! Apparently some of the shrapnel made it's way to the heater core and clogged it up or caused a small leak that eventually turned catastrophic. With 300k miles on your truck, a new engine and all new cooling system, it could very well be the heater core.
And if you have ever wondered how a car or truck is built.......they start with the heater core and work out in all directions!! It is a BITCH to get to!!
Good luck!!

 

So we have new symptoms after changing the engine. Are you sure it's overheating, or could the gauge be lying?

You replaced the fan clutch, but is the fan shroud still in place? Does the A/C condenser have dead cats and birds in it preventing airflow to the new radiator? You have a 2001 and I'm pretty sure that has a plastic intake. You could be losing coolant from a warped/cracked manifold.