Hi Everyone. There is a small hairline crack in the top driver-side plastic of the radiator (91 Buick PA). Coolant is leaking very slowly out of the crack. Is there any way of fixing this outside of replacing the whole radiator?

Some radiator shops can replace the plastic tanks; however, they usually charge about as much as what a new radiator cost. Check eBay to see what you can find. Most vendors offer a lifetime warranty on a new unit, unheard of with just a tank replacement. Don’t waste your time & money on a repair, it’s much better to replace it!

I'm looking for a temporary fix that will get the car through the winter... any ideas?

You aren't going to find a temporary fix.. You could use some stop leak( I don't recommend it ) But chances are you will still have a leak and or the crack will spread..

The best thing I could tell you is if you lived really close to me I could get you a great deal on a new unit...

But I will recommend that you have a Look at www.radiatorexpress.com

I generally get my radiators from them as its easy for me to find a Heavy Duty radiator... Seems they run from $120-$140 for most of the H and C Body FWD GM cars..