2002 F150 4.2l Heater Problem

[svt_god]

My dad has a 2002 f150 4.2l that is his work truck. The A/C works great the heat... no so much...

If your in the truck and turn the dial to heat its blows hot for about 10 seconds, then goes to cold... I had though that it might be the Blender door. But after looking more into it I think It maybe some other problem.

The 2 hoses that go to the heater core the one on TOP is hot the one on Bottom is hot till you turn the heat on in the truck them it goes cold... WTF???

My dad said there should be a valve that will kill or slow the flow of hot water to the heater core but I can't find nothing under the hood... Is it in the cab?

I'm trying to help him cause his patience runs too thin when working on newer cars and trucks...

Any other ideas??

[Captain Crawfish]

pretty sure you wont find any kind of valve redirecting flow to or from the core. its probably the blend door/ vac line or one of the vacuum motors that operates one of the vent doors

[dangerous_sep]

heres some info for some test you can do. but more than likely will be the blend door i see almost twice a week with the 97-03 trucks n suvs

[SBFORDTECH]

There is a hose available from ford and probably aftermarket that has a restirctor in it to limit coolant flow. may be a resricted heater core.

[svt_god]

Fixed it today. Flushed the heater core only bunch of crud came out and heat is back to working... He fushed the whole system awhile back, but I guess all the gunk moved to the heater core...

Anyways thanks for ya'lls help!

[appelingogt]

keep an eye on your floorboard...heater core may decide to start leaking...

[JimD]

keep an eye on your floorboard...heater core may decide to start leaking...

Yep probably.