Heater Core Help

[GeneP]

Did a search here & got some info but would like more input.
Wife's 97 S10 Blazer (Actually GMC Jimmy), for several months its been leaving spots in the driveway been drivin me crazy figuring out where its coming from. Last couple weeks they're getting bigger. Directly under tranny but not tranny fluid. By the way the actual heat it puts out sux. Crawled under it today and found drops of antifreeze hanging from shifter linkage on tranny. Just above that is a 1/4" line cut off at a 45 Degree angle. Is this a vent or drain line for the heater core box that is the source? If not what is it? 2nd to replace the heater core the Chiltons I have ain't much help. Do I need to remove the dash? Or what sequence to I start takin stuff apart to get to it. Although I think the heater core might be leaking the floor is dry....... Any & all recommendations would be greatly appreciated.

Gene

[hakogen]

does it smell like coolant in the cabin of the vehicle?

[Cam1959]

Maybe one of the 2 tranny cooling lines that circulate coolant from radiator to tranny, are off or leaking ?

I think those metal lines have threaded end fittings to connect to tranny. Not sure. Maybe short rubber hose on that end for slight movement.

Check those lines and fittings for leaks. Also check all clamps that loosen in time. My heater hoses>heater core pipes clamps, need snugging up almost every year. Cound leak there and run down fender to drip under middle.

Poor heat output maybe due to low coolant ... air build up in high heater core hose, disrupting flow of coolant thru core. For that I disconnet the rad cap and upper heater hose from engine side, hold hose high and fill up with coolant then quickly reconnect.

I doubt your heater core is leaking. Mine has no leak drain line. It just dripped out front passenger floor air output or from box seams to carpet.

To get at it I had to remove glove box door ... upper right air vent louver ... dash fasterners epescially right half ... as i only needed to move right side of dash up about 2 inches to easily get at heater core box covers. the first cover was cosmetic. i did not put that back, so i'd more easily know if it leaked at core again. remove box cover and you see core.

coolant in here could have run down core pipes from leaking hose to pipe clamps so be sure under hood clamps have not leaked.

be very carefull forcing core out and another one in as those copper pipes are weakly soldered to core and you can easily crack the solder that holds and seals those pipes. trucks with A/C have longer pipes.