No heat and low mpg...Coincidence...I think not

[twh34d]

Alright, I've got no heat on from my vents on my 94 XLT. Only after driving it for 15+ minutes will it get luke warm. I just had the system flushed a few months back. Temp guage moves but always hangs out near the cold side of the guage (been like that forever). I've read all the threads and I'll probably end up flushing my heater core. That seems easy enough to do from reading some thread in here. Also, how could it be a thermostat problem? If the thermostat sticks closed, would the heater core get any flow? Also, I've noticed that I'm not getting my usual 15-19 mpg lately. I've been losing about 50-70 miles a fill up. I think I read somewhere that a cold engine doesn't run as efficiently as a warm/hot one. I smell two problems related.

 

[DeRocha]

Alright, I've got no heat on from my vents on my 94 XLT. Only after driving it for 15+ minutes will it get luke warm. I just had the system flushed a few months back. Temp guage moves but always hangs out near the cold side of the guage (been like that forever). I've read all the threads and I'll probably end up flushing my heater core. That seems easy enough to do from reading some thread in here. Also, how could it be a thermostat problem? If the thermostat sticks closed, would the heater core get any flow? Also, I've noticed that I'm not getting my usual 15-19 mpg lately. I've been losing about 50-70 miles a fill up. I think I read somewhere that a cold engine doesn't run as efficiently as a warm/hot one. I smell two problems related.

Its more likely the thermostat is sticking partially opened. When this happens the system is being over cooled causing you not to have cabin heat. During normal operation a theromstat is contantly opening and closing to keep the engine at a constant "Normal" temperature. If the thermostat sticks open the engine will not be able to build any heat (Unless you idle the vehicle for a few minutes).. When you're idling the vehicle it isn't getting any wind through the radiator to cool it so the temp will climb into the normal range (At which point you should have cabin heat).. As soon as you start driving it will drop right back down to cold..

 

[Peteyscn24]

I had the exact same problem with no cabin heat in mine. The thermostat is a fail safe thermostat and when they fail they stay open to prevent your car from overheating. I second DeRocha

 

[snoborder42]

I had a very similar situation to this. I had very little, luke warm heat no matter what kind of driving I did. And the little heat that I did get took about 10-15 minutes of driving to get it. I finally changed the coolant and thermostat and I had heat nearly instantly.

It turned out that the thermostat was stuck wide open so the coolant never got up to operating temperature, therefore there was very little heat inside. After all was fixed, my heat works like a champ and gas mileage went up about 1-2 mpg

 

[DeRocha]

Yeah forgot to mention that as Snoborder42 wrote when the engine is not in the normal heat range it will use more fuel..

 

[twh34d]

Thanks guys, I'll check the Thermostat first. Anyone know of a good link to how to replace a thermostat?

 

[BrooklynBay]

http://www.explorerforum.com/forums/showthread.php?t=199949

 

[vroomzoomboom]

if all above doesnt work, you mite also have a bad fuel pressure regulator. i have a 90 ranger that had the same problems, was running really cold, and drank gas like crazy. but, i also had a lot of snow turn black in the back of the truck. was raw unburnt fuel. the easiest way to check if this is your problem is to check the fuel pressure while it is running.