My heater isn't blowing hot air and according to some of the other threads it's either the thermostat or heater core. Does anyone know what the normal difference is between the two hose's after the car has warmed up? I have a laser temperature sensor and I measured 160+ for the upper, and about 110-120 or so for the lower. Does that seem like the thermostat might be stuck closed? The temperature gauge seems to be working fine because it goes to about the halfway level after driving about a mile or so and doesn't fluctuate. If it's the heater core, any idea how much to repair/replace? I wish I could do the work on the thermostat myself but I'm not good with cars, even with the Haynes manual. Also, can someone point out where the coolant would flow from the engine thru the firewall into the heater core? What temperature should those be? AC/fan, works fine. Thanks for all the help!

 

Your radiator temps are about normal. the heater core hoses go into the firewall behind the transmission, they come off of the engine by the trans. two hoses about 5/8 - 3/4" in diameter. one goes out of below the thermostat housing, the other goes back into the pipe that the bottom rad. hose connects to. If anything a thermostat stuck open will cause cold engine temps, but you will get heat by 160 for sure.
check your temp at the radiator cap and see if you get around 200.

 

Well, considering that the stock thermostat opens at 190 degrees and that you're only getting 160+, it would seem that the thermostat could possibly be stuck open. Does the upper hose ever go up higher than that? What are your local temps?

 

I ran it for about half an hour, 20 miles and the temps on both upper and lower went to 180-190 and the radiator cap was about 200. Local Temps were about 70 degrees. So the hoses going to the heater core are behind the transmission? Can anyone point out where those are? I looked thru the Haynes manual and there is a picture but I can't tell where. What about seeing if the "blend" door? It's going to be very expensive for me to have the heater core looked at from what I've read so I'd like to do as much troubleshooting as possible before I have to go that route. Thanks for all the help!

 

i looked at mine (93) and they go into the firewall in the middle behind the engine. just look for 2 hoses, its that easy. if those hoses are both hot then your temp door is probly not moving. how long have you had your car? maybe someone looped the lines because of a leaky heater core.

 

if the hoses were looped, where would they do it and what would it look like? i will look for the 2 hoses tomorrow. what would cause a heater core to leak? i purchased the car recently and i don't have very much of a history. can i move the temperature door manually? thanks for all the help

 

heater cores just leak from cracks if they have plastic tanks or corrosion, it happens more often than you think,its nothing but a small radiator.what year is your car and what engine?, this would make it much easier. then i can take some pictures of stuff i have and point you to it.

 

Most likely if they looped hoses it's behind the engine where it would NORMALLY go into the firewall. I.E. middle behind the engine. Look on the firewall fer where 2 1/2' or 3/4" (I can't remember what size they used... I think 1/2") hoses would connect and look for a hose that is close by going from one pipe to the other. It will be obvious if they looped it and likely if it IS looped, you have either a cracked or clogged heater core. have fun on that one as you have to pull a good chunk of the dash out to replace it.

 

thanks for all the help, I never got a chance to look to see if the hoses were looped because I've been busy. I drove it to work today and tried the heater after 3-4 days of driving without even turning it on, and it works! In fact, it got so hot that I had to roll the windows down because I didn't want to lose the heat! No idea what fixed/caused the problem but I'm not going to complain.

 

Either the door was stuck or it had a clog. if it works now i'd shoot for the hot / cold door sticking.