No heat!
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Senior User
Joined: Feb 2003
Posts: 395
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From: South Carolina
No heat!
94 Ranger 4.0, 5-speed. No heat. Just blows cold air, even after motor is good and warm. It's been taking quite a while to ever blow warm air in the mornings, so I changed the thermostat, thinking it may just be sticking, but now it won't blow warm at all. Motor still gets warm (a little past halfway on the guage), but doesn't overheat. Coolant was very rusty, and no leaks into the floor underneath core area. 158000 miles. Have changed heater core twice, with the last time within the past year.
Been reading a lot about blend door issues here. Is that the same as the old style cable actuated hot/cold valve that used to be plumbed into one of the heater hoses? Or does this truck still have one of those in addition to the blend door?
Been reading a lot about blend door issues here. Is that the same as the old style cable actuated hot/cold valve that used to be plumbed into one of the heater hoses? Or does this truck still have one of those in addition to the blend door?
Laughing Gas
Joined: Jul 2002
Posts: 769
Likes: 12
From: Moneta, VA
Could be the blend door, which is probably contributing to the warm but no hot air issue, but I'm going more conventional here.
Since it did have some heat before you changed the thermostat, I believe you still have an air lock in your heater core. Loosen the return heater hose with the truck at operating temperature and see if antifreeze is coming through. Don't remove the entire hose all at once or all the pressure will come off and antifreeze will go everywhere.
I don't know about the cable issue, I know my '95 is vaccum operated, but it's different from the '94. Be glad you have the '94 if you have had to replace the heater core twice in the past year, '95+ is much more difficult.
Also, if the cooling system is so nasty, the new heater core could be stopped up again causing the low heat issue. This is especially true if you used a flush to clean the system, some of the crud could have came loose and got in the heater core.
Maybe someone else has some input on the blend door, I'm not that familar with them on the Rangers.
Since it did have some heat before you changed the thermostat, I believe you still have an air lock in your heater core. Loosen the return heater hose with the truck at operating temperature and see if antifreeze is coming through. Don't remove the entire hose all at once or all the pressure will come off and antifreeze will go everywhere.
I don't know about the cable issue, I know my '95 is vaccum operated, but it's different from the '94. Be glad you have the '94 if you have had to replace the heater core twice in the past year, '95+ is much more difficult.
Also, if the cooling system is so nasty, the new heater core could be stopped up again causing the low heat issue. This is especially true if you used a flush to clean the system, some of the crud could have came loose and got in the heater core.
Maybe someone else has some input on the blend door, I'm not that familar with them on the Rangers.
Moderator
Joined: Jan 2004
Posts: 13,851
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From: SW Va
With the engine fully warmed up, feel both the underhood heater hoses. If one is hot & the other is cold, suspect a clogged heater core.
If you suspect the core is clogged, remove both heater hoses, attach some spare hose to both nipples & try "back flushing" the core, by flowing water opposite the normal flow direction. Be careful not to apply full water system pressure, lest you rupture the core.
Remember it operates at about 16 psi, not at 60 psi of a hosehold water system.
If both are hot, the heater core is likely ok, so suspect a temperature or function cable adjustment, or flaper door problem.
You can inspect them by dropping the glove box door down, to access their fastening & adjustment points.
Let us know what you find.
If you suspect the core is clogged, remove both heater hoses, attach some spare hose to both nipples & try "back flushing" the core, by flowing water opposite the normal flow direction. Be careful not to apply full water system pressure, lest you rupture the core.
Remember it operates at about 16 psi, not at 60 psi of a hosehold water system.
If both are hot, the heater core is likely ok, so suspect a temperature or function cable adjustment, or flaper door problem.
You can inspect them by dropping the glove box door down, to access their fastening & adjustment points.
Let us know what you find.
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Senior User
Joined: Feb 2003
Posts: 395
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From: South Carolina
Thanks fellas... but looks like I may have panicked prematurely. It appears that it was just low on coolant. I guess I just didn't get it full enough over the weekend when I changed the t-stat. You know how it cycles and you can think it's full when it's not really... I reckon that's what happened, cause I pulled the cap this morning before I cranked it and didn't see any water, so I took a hose and topped it off, cranked it up and within about ten minutes it was blowing very hot air and the temp guage never got even close to the hot mark. Water is still very nasty - foamed up a lot when I refilled it today, so got to get that flushed real good. I'll probably start another thread about that. Thanks again for the help. Sorry to have cried wolf!
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