S10 heater core issues

I got a surprise while driving back from picking up my son from a sleepover this past weekend. And not a good kind of surprise… no, more like the kind that costs you a bit of money and a lot of time.

I was pulling onto the highway and giving it some gas to merge into traffic when all of a sudden I got a face full of sickly-sweet coolant smell coming from the vents. Eric and Jessica were in the truck too, and they were less than happy about the smell. At first, I thought it might be a rad hose or something. I watched the temps for a while but they stayed normal. No smoke or anything coming from the engine bay, and no dash warning lights. When the windshield started fogging up, I realized it was likely an issue with the heater core.

After some research on Reddit and in the S10 forums, it turns out that replacing the heater core requires removing the entire dash and will likely take an entire weekend. It’s one of the most tedious jobs related to these trucks.

I’m going to attempt to back-flush the core and see if that helps. If not, I’ll just bypass the heater core until my new one gets here and I’ll replace it as soon as time permits.

Ah, the joy of owning a 22-year old truck.

UPDATE: I chose not to back-flush the heater core because it’s beyond saving, and I have a brand new one from Rock Auto that I’ll install. In the meantime, I’ve bypassed the heater core for now.