Heater problem Mustang GT 89

rs2600 · 11-29-2008, 08:47 AM

Just bought a 89 GT conv. Problem is, there's no heat inside the car. Engine temp is within normal range and fan is working. Hoses in the engine compartment going to the heater and comming out again are just lukewarm. When idling, a litter more heat comes through the defroster bur as soon as the car starts moving it gets cold again. What could to be the problem?
/Matt

**mack1** · 11-29-2008, 11:37 AM

Hi rs2600 and welcome to TSF

Normally, the hose from the engine to the heater would be hotter than the return hose. Even if there is only little flow through the heater. Did you check the hose temperatures with the engine idled up (feed it a little gas). On slow idle, some engines won't pump water through the heater core. Make sure the radiator is full to the top with water. I had a truck once that would tell me when the water was low by giving me cold air through the heater, but the engine was still normal temperature.

Does the hose from the engine to the radiator feel hot? I'm wondering if the heat gauge in the car is lying about the temperature.

To make sure the heater core is not mostly stopped up, disconnect the hoses at the engine and push water through the heater using a water hose. Be sure the heater is truned on if there is a water valve in the loop to the heater. Water pressure is usually about 80 psi, so be careful and don't press the hose too hard against the heater's hoses. Push the water both dirrections through the heater core. The water should flow easily in both dirrections unless there is a stopage, or a water valve is not turned on.

Hope this helps,
Mack1

**Midnight Tech** · 11-29-2008, 12:36 PM

Any evidence of any sort of performance work being done to the car? It's possible the previous owner took the thermostat out to make it run cooler.

11-29-2008, 08:47 AM	#1 (permalink)
rs2600 Registered User Join Date: Nov 2008 Posts: 2 OS: xp	Heater problem Mustang GT 89 Just bought a 89 GT conv. Problem is, there's no heat inside the car. Engine temp is within normal range and fan is working. Hoses in the engine compartment going to the heater and comming out again are just lukewarm. When idling, a litter more heat comes through the defroster bur as soon as the car starts moving it gets cold again. What could to be the problem? /Matt

11-29-2008, 11:37 AM	#2 (permalink)
mack1 TSF Articles Team Join Date: Nov 2007 Location: Texarkana, Texas Posts: 1,245 OS: xp sp3 My System	Re: Heater problem Mustang GT 89 Hi rs2600 and welcome to TSF Normally, the hose from the engine to the heater would be hotter than the return hose. Even if there is only little flow through the heater. Did you check the hose temperatures with the engine idled up (feed it a little gas). On slow idle, some engines won't pump water through the heater core. Make sure the radiator is full to the top with water. I had a truck once that would tell me when the water was low by giving me cold air through the heater, but the engine was still normal temperature. Does the hose from the engine to the radiator feel hot? I'm wondering if the heat gauge in the car is lying about the temperature. To make sure the heater core is not mostly stopped up, disconnect the hoses at the engine and push water through the heater using a water hose. Be sure the heater is truned on if there is a water valve in the loop to the heater. Water pressure is usually about 80 psi, so be careful and don't press the hose too hard against the heater's hoses. Push the water both dirrections through the heater core. The water should flow easily in both dirrections unless there is a stopage, or a water valve is not turned on. Hope this helps, Mack1 __________________ "If you like yourself others will like you also" me "Don't drink downstream from the herd" Will Rogers Submit New Articles Here Last edited by mack1; 11-29-2008 at 11:40 AM.

11-29-2008, 12:36 PM	#3 (permalink)
Midnight Tech Admin/Head GreaseMonkey/Igor's alter ego/Grand Exalted PoohBah Join Date: Dec 2001 Location: SC Posts: 2,924 OS: Windows XP Home/Pro SP3/Windows 98SE/Fedora Core 6/RH 7.2 with Autopoint/TAMS II	Re: Heater problem Mustang GT 89 Any evidence of any sort of performance work being done to the car? It's possible the previous owner took the thermostat out to make it run cooler. __________________ Please post all questions in the appropriate forum. Questions sent by email or PM will not be answered. Sharing my life...with my Imzadi! Interested in Trek gaming? Check out the Dynaverse! Proud supporter of the Carolinas Aviation Museum. If we have helped you in any way, please donate to keep TSF up and running!