Our Peugeot 306 started getting a fishy smell last year when we had the heater on. It seems that its not there immediately (unless the engine is warm) and only lasts a few minutes (or we get used to the smell and can't smell it). The smell is very similar to the smell I get when I sniff the cooling water so I'm guessing the heat exchanger may have a leak. Water level isn't going down, and there's no signs of leaks in the car (and it smells fine during the summer, when the heater isn't on).
I'm not too fussed about it (need the car, its very inconvenient to get it into a garage, plus I'd prefer not to have to spend any money!).
Any ideas what it could be? I've changed the coolant and it made no difference (smell was still there in the radiator anyway).
Any simple solutions, and if not - what sort of cost I should expect to get it fixed (I assume a new heat exchanger + labour).
Thanks
D