I had noticed that sweet smell when the temperature was turned up and air flowed through the core, but had no major leaking. My core was leaking slightly and showing corrosion in exactly the places these things always fail, namely, where the plastic tank meets the aluminum heat exchanger.
I bought the $39.00 Swedish Car Parts Estonia-made heater core that has so far gotten good reviews for quality and function. I received mine promptly, and it does look nicely manufactured. This core differs from all of the others in that it is made differently from the Volvo OEM core. The joint between the aluminum and the plastic side tanks where the standard cores always fail is "crimped over" with metal for what appears to be a much more positive bond that will be less likely to come apart from repeated heating and cooling cycles. The plastic tanks are now made of black plastic which the vendor says is superior to the previous "ivory" colored material. It fit perfectly, had the proper hole for the screw holding the pipes in, and required no modification whatsoever.
Post-Install Note: I do detect an oily smell in air coming through the heater core after heating it up thoroughly. I smelled it right up close before installing it and smelled nothing. I'd recommend you degrease the metal part of this thing thoroughly before installing.
There has been some talk about whether or not to use the o-rings supplied with this core. Some people have had leakage with them while others have had no problems. Some recommend only using OEM Volvo o-rings despite the $3.69 price because they are slightly thicker than the o-rings supplied with the core. I had obtained 6 pieces of Volvo Heater Core/Hose O Ring (850 C70 S70 V70) - Santech 3545586 from FCP which are green in color and go for $0.29 each. In comparing the Santech o-rings with the supplied o-rings, it was clear that the Santech o-rings were just slightly thicker and therefore had a slightly large outer diameter. The Santech rings appear to be well made and of good quality, so I used them in joining the heater core to the pipes. They fit perfectly and I have seen zero leakage after taking the car out for a good run.
One last thing: Go to Home Depot or somewhere and get 3 mil contractor trash bags. I laid the open end of one of these under the core when I released the pipes and just let whatever came out drain into the bag. There wasn't too much, and when it stopped draining, no more came out while I was working. Afterwards, I got a funnel, cut off one bottom corner of the bag, and just returned it all to the coolant overflow tank. No draining of the radiator. No clamping hoses.
If you take your time (and remain calm) replacing the heater core in this series of V70 is really not a bad job. When I did this on my 2000 Ford Taurus, it was necessary to remove the entire dashboard and lay it on the front seats, so consider yourself lucky!
