Son called from College 800 miles away- S10 is steaming up the windshield, appears to be coolant. Likely culprit- heater core.

Did some research, replacing heater core is a major job. Not all that tough except locating about six hidden screws. Job is super time consuming, and lots of things can go wrong if someone doing the job is sloppy and/ or inexperienced. Called the local Chevy dealer- $1400 for the replacement.

Looking for any suggestions on best way to approach it. I am assuming it is in fact the heater core and not a clogged heater core- I flushed the heater core four years ago when I replaced the LIM gasket, water pump, and radiator. I am speculating after replacing all of that and new DEX, the core should not be clogged.

Install a bypass kit. ie, remove the heater core hoses from the fire wall and install a piece of pipe to reroute the coolant. Tell him to dress warm.

Yes, I've heard the S10, Blazers heater core is a PITA to get out. 6-8 hours of labor to pull the whole dash out.

I am thinking about driving out to my Son, leaving him my truck, and taking his truck back to PA and do the work myself. If I get his truck to PA, I will likely do a tune up, replace the ball joints, idler arm, and a few other things. Issue comes as at 800+ miles each way, that is 3200+ miles..........

Might only be 1600 miles driving for you if your son plans on coming home from college for Thanksgiving vacation. That would give you a few weeks to make needed repairs and he would be doing half the driving after the completed swap. Like Mike says bypassing the heater core is a temporary fix that he could do, but if he goes to school where it gets cold he'll miss the defroster more than the heater.

2004 Bonne SLE
1971 Chevelle SS

Looks like the plan is to drive out to him on Monday and leave him my truck, and drive his S10 to PA. Work on his S10 and do the following:
* replace heater core
* replace passenger mirror
* upgrade fuel injectors to spider configuration (already have upgrade kit)
* replace front rotors and pads (already have rotors and pads)
* replace idler arm (already have part)
* replace door hinges
* replace lower and upper ball joints- they were good two years ago but truck is at 165k miles- might as well do it while everything else is being done.3
* replace plugs, wires, and distro cap
* flush trans axle
* inspect vacuum hoses
* possibly replace tires (hope not- S10 is a ZR2 and tire is somewhat pricey)
* replace rear end oil

My Son can then pick the truck up at Christmas- I don't have the time to get it all done before Thanksgiving. The other option is for me to fly to Phoenix and pick up the Bonneville, drive it to Illinois and leave it with my Son, and then bring the S10 to PA. The plus with this is the Bonneville is FWD and easier to drive in the winter than the RWD F-350.

Sounds like a plan, you might even get some help out of your son during his Christmas break if you run short on time with that extensive "to do" list!

2004 Bonne SLE
1971 Chevelle SS

Yes the S10 heater core is a PITA! You do need to remove the entire dash assy. The book calls for you to evacuate the AC, take out the inner fender and remove the outer AC assembly from the fire wall because there is one bolt under it that holds the inner heater box to the fire wall, I cheat. I remove the dash take all the bolts loose from the heater box except for the hidden one, I take my pencil torch and heat up the plastic and flex the heater box away from the firewall enough to sneak the heater core out.

I did a lot of heater core on the blazers and s10 when I worked at the chevy dealer. I never evacuate the a/c. you can get to the so called hidden bolt. it a pain but manageable. once the inner fender is out.

if you dont clean the inside window they fog up like that, i would have him do it and make sure it comes back before you get too far

Picked up the S10. 1500 miles round trip in under 26 hours. Drove myself, 3 hours sleep after I picked up the S10 in the Indiana Toll Road service plaza. Sleeping io a 98 S10 standard cab with a floor console is tough; can't lay across the seats at all, and no recline of seat in a S10 standard cab....

Arrived at my Son'* college at 10pm, and he gave me a squeegee to clean the inside of the windshield while driving. For three hours I drove through construction and Chicago traffic, could not see much, but it was late so traffic was not so busy.

After awaking from a 3 hour nap service plaza; it was raining. I had no choice but to turn on the front window defroster. Low and behold- it actually cleared the inside of the windshield after a few moments. No idea why the inside windshield fogs up when the defroster was off, but when it was things worked ok except a bad smell of coolant vapor in the cabin.

Ordered the OEM heater core. Amazon was $10 less than RockAuto, and also had free two day shipping. RockAuto wanted $7 for shipping and it was take 4 days for arrival. Amazon often beats RockAuto on cost and delivery of auto parts.