Help!!!!!I bought a 98 150 w/4.6 only to find out later that it had no heat,took a chance and replaced the heat/ac temp switch,no heat.Took it to a ford dealer and after they 1st said it was a plugged heater core,then decided it was a bad blend door motor(replaced),after 3 days and 346.00 decided they couldn't help me.Drove it home to michigan w/no heat(very cold trip)Took it to a shop and had the core,thermastat replaced(606.00)still no heat.Found it to have very little coolant flow,checked the water pump and found all the impeller blades rusted away(replaced it).truck never ran hot all the way home 980 miles with a bad water pump,now i have heat at idle but if you raise rpms it blows cold and coolant blows out through overflow tank then when you release the pressure the temp guage drops to below cold and truck starts to run rough.Then all of a sudden the temp will spike to hot, oil like comes on for about5 seconds and starts missing.This truck ran perfect all they way home but now is like a monster.Any ideas????? thanks

 

Sounds now like you might have a blown headgasket. From what you said about the waterpump I would think about a engine before jumping into a headgasket.

 

sell it buy beer

 

Yes i thought of a head gasket and believe that may be the problem,the oil is ok w/ no coolant in it but i checked tonight and the coolant smells like exhaust.Looks like i 'm going to check into a 5.4 swap,are the 2000 and newer 5.4's free of the spark plug blowout problems i've read about?

 

i have a 2000 5.4 and they claim it "could" have a spark plug blow out issue, but i have 87,000 miles on it with out any problems at all!