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I have a 1994 f150, xlt, 4x4 with a 351w. The heater core has been replaced, 4 different thermostats, water pump replaced, cylinder draw down test, and cylinder pressure test. Still no heat.
Ok so an update on what was found. Upon taking it to a 3rd mechanic, an old school mechanic, it was determined that the bypass hose and the return from the heater core were installed backwards on the waterpump. Still in testing mode for a day or two just to confirm its working now.
Whats the best way to visually check that the blend door is actually closing all the way as it should? The one under the hood I would assume to remove the blower motor and verify but what about the one under the dash?
I have the same issue in my '93 F150 6 cyl. I've watched a number of Youtube videos saying that a pen or such from the dash can fall down and block the blend door from fully closing and that would create the no heating issue. They say you can reach in and feel around for a blockage although I've yet to try. I'll be tackling this issue this weekend and am following this thread with interest.
Ok so beyond frustrated and confused. The heater control door was checked, it closes as it should. It was thought that maybe the heater core was air locked. So I got a radiator/ cooling system test kit, took off the return line from the heater core to the water pump. Slowly started pressurizing the system until I had coolant coming out of the heater core. I put in a "T" with a needle valve on top. Had great heat. Took off for a test drive. Lost the heat. I left the cover for the heater core off so I could verify the whole heater core was hot. A mile down the road, I lost half the heat from the heater core. So my thought was air locked. I vented the system, still no heat. Half the heater core had cold air blowing through it.
If it is a possible small head gasket leak, causing exhaust gas into the system, nothing has been proven that with all the tests. Any other ideas?
what temp thermostat(195*), is/was it put in right, when water pump replaced,did they give the the correct one, reverse rotation goes on our truck, was the belt routed correctly, should have sticker under hood
Yeah that rad is too big for your climate, I have been saying for years that it is possible to overcool some of these motors but nobody believes me. All the 2.3L Rangers I ever had as well as the stock 5.0 trucks needed a winter rad cover to generate good heat in the winter up here where I live.
The truck doesn’t overheat. I just am not getting heat out of the heater core. Almost as it is airlocking. There is only 1 water pump for this truck. It is the correct pump. Belt is routed correctly. Acting as if there is air being introduced into the system. Causing an airlock or no flow through the heater core.
Now we need a test to determine if there is air getting into the system, and from where. You got heat when you bled the system and confirmed coolant flowing through the heater core, so you know the core is good and the system works as it should when it is full of coolant.
If there is an exhaust leak into the cooling system, where is the coolant going? Is the engine burning the coolant, producing white smoke and telltale signs of coolant in the combustion chamber? If the coolant isn't being burned, is it filling the expansion tank? Someone must have tests to help determine if, and where a leak is to get air into the cooling system. It would seem you have proved that the problem is not with the heater core, or heater system.
I know it’s a long shot but thoughts about this? The radiator on my truck is a 4 core. Definitely not the standard. I am wondering if the water pump cannot pump enough volume through the engine block, radiator and the heater core. Do I need a smaller radiator or a high volume water pump? Just a thought? Question?
Yeah that rad is too big for your climate, I have been saying for years that it is possible to overcool some of these motors but nobody believes me. All the 2.3L Rangers I ever had as well as the stock 5.0 trucks needed a winter rad cover to generate good heat in the winter up here where I live.
I know it’s a long shot but thoughts about this? The radiator on my truck is a 4 core. Definitely not the standard. I am wondering if the water pump cannot pump enough volume through the engine block, radiator and the heater core. Do I need a smaller radiator or a high volume water pump? Just a thought? Question?
That doesn't make sense to me. Once the system is full the pump should move the water, regardless of the size of the rad. Remember that liquids don't compress. I'd think that if you had a weak pump you'd have more heat, not less, or at least the engine would overheat. Where is your coolant going if it makes good heat in the cab when you filled and bled the system, then lost heat after driving, creating what you thought was an airlock in the heater core, or heater core lines? If any air got in, the displaced coolant had to go somewhere.
Like I said before, I've never had trouble with my truck making enough heat in the cab and I live in a place that is colder than where Conanski lives. However, the easiest thing to do would be to put some cardboard over the grill to restrict the air flow and see if that makes a difference in your cabin air heat. An old box and a couple of zip ties and you'll know pretty quick if it helps. I do seem to recall when I first acquired my truck that the fan clutch was stuck so the fan was always pulling air, even at 40 below, and I believe I was low on cab heat at that time. A new fan clutch took care of the problem and the windshield would defrost much better. If you haven't checked your fan clutch, maybe give that a look.
I've never had trouble with my truck making enough heat in the cab and I live in a place that is colder than where Conanski lives. .
Does your truck have a 4-core rad or the stock 2-core?
Air in the coolant system is a possibility, it should all eventually work it's way out and when it does the level in the rad will drop, but to speed that up park the truck somewhere it is nose high or jack up the front, and run the motor with the rad cap removed.. this should purge any air trapped inside. If there is air in the system you should hear water gurgling through the heater core immediately after the engine is started, but this will stop as the water pump circulates coolant and fills up the core.
Here is the thing with these oversized rads. The thermostat will ensure that the engine's internal temperature gets there quickly and is maintained, but every time the thermostat opens it's now dumping hot fluid into a rad that not only holds a larger volume of fluid but has twice the external surface area, both of which cools it much faster, so when outside temps are really cold it will take a lot longer for the overall coolant temp to stabilize and that median coolant temp will not be as high as it is with a smaller rad. The problem is the bigger rad can cool fluid faster than the engine can heat it, great for driving through the desert in the summer but bad for driving anywhere in the north during the winter.
Does your truck have a 4-core rad or the stock 2-core?
Air in the coolant system is a possibility, it should all eventually work it's way out and when it does the level in the rad will drop, but to speed that up park the truck somewhere it is nose high or jack up the front, and run the motor with the rad cap removed.. this should purge any air trapped inside. If there is air in the system you should hear water gurgling through the heater core immediately after the engine is started, but this will stop as the water pump circulates coolant and fills up the core.
Here is the thing with these oversized rads. The thermostat will ensure that the engine's internal temperature gets there quickly and is maintained, but every time the thermostat opens it's now dumping hot fluid into a rad that not only holds a larger volume of fluid but has twice the external surface area, both of which cools it much faster, so when outside temps are really cold it will take a lot longer for the overall coolant temp to stabilize and that median coolant temp will not be as high as it is with a smaller rad. The problem is the bigger rad can cool fluid faster than the engine can heat it, great for driving through the desert in the summer but bad for driving anywhere in the north during the winter.
Ok so what we found out. There was a vacuum leak so the blend door wasn’t closed. On top of that we had the entire system power flushed. It is believed that the radiator has so much gunk in it that it kept flowing back and forth stopping flow in the heater core. I had it flushed twice, I have had heat since. Later this summer I am going to put a new radiator in the truck and have it flushed again.
I do seem to recall when I first acquired my truck that the fan clutch was stuck so the fan was always pulling air, even at 40 below, and I believe I was low on cab heat at that time. A new fan clutch took care of the problem and the windshield would defrost much better. If you haven't checked your fan clutch, maybe give that a look.
