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So im working on this 5.4 2000 f150 4×4 auto tranny…has 0 heat
THINGS IVE DONE
–TOOK DASH OUT –VENT DOOR WORKS AND HEATER CORE HAS 0 LEAKS
–CHANGED THERMOSTAT
–FLUSHED COMPLETE SYSTEM
STILL NOTHING!!
–REVERSE FLUSHED HEATER CORE W BLEACH WATER AND CLR
–TOPPED UP FLUID
RAN THE TRUCK AT 2500 RPM WITH THE CAP OFF THE FILLER BOTTLE FOR 20 MIN HAD HEAT THEN
THE HEAT REMAINED AT IDLE..
SO I LET IT COOL DOWN–CLEANED THE SHOP ECT
STARTED IT COLD AND NO HEAT AFTER 15 MINS IDLE AND NO HEAT AFTER 15 MIN DRIVINGWHAT DO I DO NOW????
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Are the heater core hoses hot going in and out or cold?
https://www.ericthecarguy.com/faq/solving-automotive-hvac-problems
Check your heater core hoses both inlet and outlet. Are they hot? Truck may have a valve in the heater core line that shuts the coolant flow off that is stuck closed. I have also seen water pumps unable to pump coolant into the heater core but pump enough to not let the truck overheat. Take the inlet hose going to the heater core and see if it is pumping coolant out when you run the engine. Lastly you said the the vent door works but you need to see if the blend door and its motor works.
[quote=”ArmedsouthernEr” post=175630]Check your heater core hoses both inlet and outlet. Are they hot? Truck may have a valve in the heater core line that shuts the coolant flow off that is stuck closed. I have also seen water pumps unable to pump coolant into the heater core but pump enough to not let the truck overheat. Take the inlet hose going to the heater core and see if it is pumping coolant out when you run the engine. Lastly you said the the vent door works but you need to see if the blend door and its motor works.[/quote]
THERES NO VALVE
ALSO YES I FUNCTIONED THE DOOR AND SEEN IT OPEN AND CLOSE..ALSO WHEN I FLUSHED THE HEATER CORE I DID A FLOW TEST AND THE FLUID PUMPS OUT OF THE SUPPLY LINE FROM THE MOTOR FINE[quote=”Disabled Automotive” post=175636]i would say the problem is the core.[/quote]
i did have heat after constant rev 2500 and at idle after but once it cooled down after i shut it off back to cold
It sounds like air is still in the system.
https://www.ericthecarguy.com/faq/solving-automotive-hvac-problems?start=5#HeaterProblems
If both hose are cold going in and out the core won’t do anything because it isn’t receiving hot water.
I flowed water through the heater core…no block…i also started the engine with the hose off and fluid came from the core supply line.. its definetly a mystery as to why theres no heat thats for sure but ive bled the lines (burped) and nothing…i have to rule out air bubble because even while driving at high rpm thers no heat.. and the door functions properlly as ive tested it and it opens and closes.. the t stats opens fine as the top rad hose gets hot and the engine temp stays normal so i know i have flow…SOOOOOO there i am with 2 possabilities left…weak water pump or clogged lining in the heater core??
ive done that.. ive flushed the core backwards w aire and then put clr in it and let it set then flushed the core again w water
Well I mean if water is flowing through easily both directions I highly doubt the lining is clogged.
What gets me is that you say the heater inlet hose flows coolant when you checked it, but doesn’t get hot.
Makes me think there’s “something” floating around where the inlet hose connects to the engine, and is blocking the flow on an intermittent basis. Does the inlet hose attach to the engine near the thermostat? If the old thermostat fell apart, there could be some pieces swirling around in there.
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