Prob clogged up heater core mine did the exact same thing just replaced mine a few weeks ago works perfect after that

 

Well the saga continues. Replace waterpump old one was OK all fins intact,but with 200K on the truck did not mind that. Still having the same low heat problem. While changing pump, I removed the hoses to the heater core and first used air then a hose to blow them out. Appears the the core is open as water flows in/out just fine. Also blew air thru the block and all passages seem to be open.

Maybe it is the heater core but sure seems to pass water just fine.

Can anyone confirm (or deny) wether there is some type of valve that regulates the amount of water that passes thru the core.(2002/ 4.6) I can not find one under the hood.

My next step will be to check flow thru the core while the engine is running instead of the hose.

Really scratching my head on this one

 

I'm really dreading pulling that dash out it is my heater for, I did it on my 93 a few years back. I just don't think it's my heater core because I'm getting heat through panel (not alot) but there is some. There is a heater control valve, but not sure where that is.

 

I do not think there is a heater conrol valve. I find mixed answers but I am leaning towards there not being one. I can trace the hoses in and out to to the block and there is no valve. The hoses hook to the heater core inlet/outlet on the firewall. Can't see where there is a valve anywhere.

 

I know it's strange, auto part stores carry the part but I just can't seem to find it on the truck.

 

Ya gotta check the flow to the core and through the core while the engine is running at operating temps. Until you do that you wont know whats going on. And if the core is flowing nice with water from a hose then its not clogged.

So do you get ANY heat in the cab? Meaning...does the amount of heat fluctuate depending on whether you have the setting on panel or floor or dash?

If you're not getting ANY heat, have you checked your temp control? It opens and closes the blend door. If you pull your floor panel off its the white plastic thing with a wire run to it.

Then check the blend door, try to turn it by hand.

 

Alreaday checked blend door and motor both work fine. Until someone can shoe me different I am taking the position there is no water control valve on my truck.

I am now relativley certain that at least part of my issue is a partially blocked heater core. I flushed the system last nite and added 2 bottles of Prestones Cleaner. It is to be run in the system for 3-6 hours over a few days if needed. After about 2 hours of run time I believe I can tell a difference. I will see by Sunday for sure.

My other question is for some reson on these F150s the A/C will cycle on all settings except for "floor". I understand the reason for this but does anyone know what controls the cycleing? I think mine runs too much at least now. I do believe it is not supposed to run when the temp is below 40 according to the manual but right now here in KC the A/C runs alot even on the heat settings. Not all the time but alot

Since all the air passes thru the A/C coil before it pass's thru the heater core it seems I am super cooling the air I now need to heat.

Anyways things have improved with the flush/clean so we will see

 

I heard recylcing CLR remover (calcium, lime and rust) through the heater core with a electric pump, bucket, 2 hoses and hot warm for a few hours also works wonders.

But did you ever check the flow through the core by taking off the core outlet hose while the engine is running at operating temp?

Could try taking off your hoses and replacing them with clear hoses from home depot and then let the truck run just so you can see the flow and whats going on....without making a huge mess.

DO EVERYTHING you can before replacing the core...Its a pain.

 

Used Prestones cleaner (2 times) to flush system. Heater is back working as it should or at least much better than before. I think this has resolved my problem at least for now

 

Happy to hear this, I'm gonna try on mine this week, I've heard those cleaners are bad for your vehicle though, is this true?