I've got a 2004 F150 Lariat 4x4 with the 5.4L motor. I want to reverse flush the heater core. Which hose is the inlet and which is the outlet? Also, do I need to worry about removing the flow restrictor? If so, where is it located? Thanks.

 

I figured it out from a parts diagram if anybody else wants to know. The hose from the heater core at the firewall that runs to the front of the engine is the inlet hose and it looks like there's a flow restrictor in the end of the hose near the front of the engine.

 

Good info. Going to do core flush this weekend and did not know about flow restrictor.
Thanks.

 

I will caution anyone on flushing a heater core. For 2 reasons.

1.) If the core is clogged, this means lack of cooling system maint. Not always your fault, some of which is dealers that lie by changing the coolant in the bottle and not in the whole system, others from previous owners just not doing it.
2.) In every case that I have done this, several months later a leak developed. Again, lack of maint that caused it to clog, kept it sealed with gunk.

There are two ways you can reverse flush, once by using a garden hose and just letting the water run out backwards (being careful to not use full city water pressure), and the other method is to use very low flow with tee and bubble air into the line. You do tis by installing a fish aquarium pump into a tee, and while the water flow flowing, bubble air into the line. This is a very gentil approach that will disrupt the sediment without running the risk of over pressuring the heater core.

The last resort is a chemical flush. Each and every time I can used a chemical flush, a leak developed. This is even after following the directions to a tee. I would not recommend EVER using a chemical flush unless you remove the heater core from the circuit, and are trying to fix an electrolysis problem with the engine block. Some blocks contain minerals, and porus metal that creates electrolysis. This is one reason repeat core failures occur.