Yeah, most people don't think of it that way, but the heater core is actually a supplementary radiator. I had a very old car that was running hot, so I sourced a heater core from a junkyard, plumbed it with the heater hoses and mounted it behind the stock radiator - brought the temps down nicely.

 

If this is necessary to prevent your engine from overheating, then you need to fix your car because there's something wrong with it. You should not need to do this with a healthy engine.

 

why didn't you just fix the real issue. All that extra plumbing is more stuff that can go wrong.

 

Well, it's not quite overheating, I just turn on the heater when it gets hotter than I'd like it to get, just 'cause I like to be nice to my engines.
Also, I enjoy keeping my bikes and cars running for as little money as possible, just a silly game I like to play. After all, anyone can buy new parts, and anyone can pay someone to work on their car, but not everyone can keep a car or motorcycle on the road while spending almost nothing! I do invest in cars though. Nine years ago I put all the money I didn't spend on cars in TSLA and did very well as a result (thanks Elon!).
When I see folks driving proudly down the road on cars they spent 30~40K on — cars so complex that their owners can't possibly maintain or repair themselves — I can only shake my head. Cool if that's what's important to someone, but I'd rather drive a vehicle that's making me rich than one that's keeping me poor.