My hubby is working on a 200 F150. The heater does not get hot. He has checked the blend door and it is functioning correctly. Is there a valve on the back of the engine that shuts the water off going to the heater core? Thanks!!

 

I recently had a problem getting heat on my 97. Removed the heater hoses from the firewall and backflushed both tubes with water. Turned out to be pretty clogged . Working much better now. You can get the hose removal tool from most parts stores that have loaner tool programs. That would be my first thing to check. Make sure you run water from a garden hose into both tubes and keep going from one to the otber until you see clear water. Also, when reconnecting the hoses, make sure the connection fittings have 2 o-rings with a spacer in between. Sometimes they stay on the tube coming out of the firewall.

 

If he gets some time, its best to pull the core and give it a good shake and flush or replace it. Its been my experience that once they get that clogged, even a vigorous in the car flush and back flush, only provides marginal results.

 

Load it up with Lime Away and let that soak for awhile before back-flushing. That stuff will loosen scale and rust so it can be flushed.

 

I know on motorcycles that stuff will eat at head gaskets with aluminum heads.

 

lime away is a weak acid and will loosen the crud if left for 20-40 minutes or so. You do not want to leave it in contact with aluminum parts for 24 hours.