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88 MUSTANG Heater Not Getting Hot

10-12-2005, 08:16 AM

STILL HAVE PROBLEM WITH HEATER IN 88 5.0. Maybe you can point me in the right direction. I have 88 mustang lx 5.0. I bought the car last Nov. and the heater didn't work. The guy said it just stopped working. I changed the heater core thinking it might be stopped up. No good. I changed all the heater hoses. No good. I changed the thermostat. No good. I put a 3 core radiator because he said it would run hot in the summer. The ac works great. Is there a Heater control valve on this car and if so where is it located? I thought it would be in the line going to the heater core but its not? They sell one for it at auto zone but I see nothing that looks like it. I recently bought a high flow water pump, and another thermostat, and installed it and it still didn't help. If I turn the switch to off and run for about 5 min and turn it on heat I get a little warm air for about 15 sec. If I can't get the heat to work im going to have to sell this car. It gets cold in NJ! Any info will help. NEW UPDATE!!
Neither one of the heater hoses get hot. We took the one off on the right (the in Hose) and left the out hose on and connected a pressure pump to the radiator mouth to see if we had flow through the heater core. It gushes out. We the put the in hose back on and took off the out hose and pressurized it and it flows that way also. We jacked the car up from the front, to get air out and let it run 30 min while filling it . The heater started to get warm then hot. We drove around and it started to get cold again we checked the antifreeze it was ok added just a little. Revved the engine and added a little more. The heater started getting warm again. Closed it up. Got in it this morning and no heat. Let me tell you where my hoses run, and maybe you will know exactly if I have them hooked right. There is a pipe that comes out of the front of the lower intake manifold. It has a temp sensor in that line. It runs under the throttle body and connects to the right pipe sticking out of the heater coil. I figure that's the inlet side. Then it comes out of the heater core and connects to a pipe (and this pipe has a small hose coming from the throttle body) and then goes to the lower small pipe on the water pump. (Both little hoses that run one on each side of the throttle body get hot so they are getting flow.) There is another hose right above that one on the water pump that runs to the thermostat housing, I think this is the bypass hose. Do I have these two switched? The car runs at 200 degrees. That should be warm enough. I would think that both the small pipes on the left side of the water pump should be flowing in correct? So it shouldn't matter? This is really messing with me. Any Ideas? I checked the hot cold flap on the inside and it is working. It works by cable. I replaced the whole heater control panel and still nothing. Im open to any suggestions.

10-13-2005, 12:44 AM
the metal pipes running under the throttle body to the rubber hoses on your heater core, are they getting hot?? its dark outside right now, and I dont have ne lights, but i'll check to see how my hoses are ran in the morning to see if mine are ran like yours.

10-13-2005, 06:39 AM
Yes they get hot but Im thinking that could be from laying on top of the lower intake. Yesterday we took vice grips and pinched the top small hose (the bypass Hose I think) almost shut and the heater got hot. But while driving it it got just warm and the temp guage was all over the place. Im thinking maybe the 2 small hoses on the water pump are switched? Its like it isnt making enough pressure to produce flow thru the heater core and the bypass hose at the same time and the least path of resistance is the bypass hose. I just put a high flow Malory water pump on it. THIS THING IS OUT OF CONTROL! Please check exactly where your hoses run for me. Thanks very much

10-13-2005, 10:08 AM
on my 95 (which has a 5.0) the metal hose which is on the right side (looking at front of car) has the temp sensor on it. That same metal hose goes to the left (looking at front of car) rubber hose coming out of the heater core.

On the water pump, The top small hose goes to the thermostat housing (bypass?). The bottom small water pump hose goes to the metal hose with no temp sensor, which ends up on the right rubber hose of the heater core. hope this helps!!!

10-24-2005, 12:49 PM
Hey, this heater is still not working as it should. It gets warm but not hot. I left it running for 30 min and it is still cold in the car. Is there something else that needs to be done. I put 195 degree thermostat in it this weekend. If I turn the blower on hi it really gets barely warm. I put a 12mm socket in the outlet side hose of the heater core as I was told to do on another forum site. It wasn't even getting warm at all till I did that.Any more suggestions? It wont work good at all when it really gets cold

11-07-2005, 10:27 PM
just as a DUH question, did you check the coolant level?? I have seen cars heaters not work due to being low on coolant..

11-08-2005, 08:06 AM
just as a DUH question, did you check the coolant level?? I have seen cars heaters not work due to being low on coolant..

Yes. Read the thread and it will tell you everything. Thanks

11-08-2005, 06:25 PM
Not fimiliar with the 5.0 but it sounds like an air lock between the out hose from the heater core to the bypass.If the hose makes a valley between the two and then heats up from engine heat the water wont flow.Run the engine and then loosen the hose clamp and hopefully the air will get pushed out.Thats all i can think of. How do you shut off the heater in summer if there is no shutoff valve in either of the heater core hoses? Always use Ford thernastats as after market ones are designed a little bit different at the spring end.

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