this is from experience... you have to remove the whole dash to get to the heater core under the glove box, it took me 2 days. I would take it to the shop and let them have the headache. I guarantee that will be money well spent
Actually , the heater core doesn't have a drain
Sometimes changing a heater core can be a very big job. It is not changing the core that is hard, rather getting to it. Good luck.
Take it to a mechanic and say "will you fix the heater core?"
HEATER WISE? YOUR HEATER CORE MAY BE BLOCKED
The Heater Core will be located behind the dash. Hope that Helps.
Before CHanging the Heater Core, have you tried flushing it? I have a 99' Jimmy and have to do this every year to get my heater to work.
You will need to remove the water lines from your heater core. Remove the heater core retaining bolts. Reverse the process to install the new heater core.
Begin by removing the water supply hoses to your heater core. Remove the heater core retaining bolts. The heater core will come out. Reverse the process to install the new heater core.
Talk2DIY Automotive - 1986 Tires and Changing Heater Core was released on: USA: 14 August 2004
I had this problem before on a ranger you have to pull the dash board out and it will be right there.
Remove the water supply hoses from your 1985 Chevy heater core. Remove the heater core retaining bolts. The heater core will come out. Reverse the process to install your new heater core.
Remove the water supply lines to your 1985 Pontiac Trans Am heater core. Remove the heater core retaining bolts. The heater core will come out. Reverse the process to install your new heater core.