A few weeks ago, I asked here for advice on replacing my mechanical fan with an electric model. I thought I would share my experience, now that it is complete. Volvos don't have enough room behind the radiator for a puller fan, so I had to pick a pusher for the front of the radiator. I purchased a 12" Perma-cool fan. Perma-cools only come as a puller, but they say the fan can be reversed and used as a pusher. The instructions were terrible, they said I had to remove a allen head screw to reverse the fan - they didn't bother saying where the screw was - and there were no pictures. I figured the screw would have to be on the shaft and tried for hours feeling around inside the hub of the fan trying to find this screw. I finaly gave up and exchanged this fan for a model 130 from Flex-a-lite that already came as a pusher. The Flex-a-lite comes with a shroud and it fits almost perfectly. I just had to saw a couple of small grooves in the top of the shroud so two pieces of sheet metal from a supporting brace could fit in. The shroud fits tight verticaly, but there are about 2 1/2" of unshrouded radiator on each side. Also, because of the tight vertical fit, the shroud did not push up against the radiator like it was designed to do.
I was concerned about the unshrouded area, and the possibility of air escaping around the shroud because of not being pressed up against the radiator. So, I tested it by covering all the areas on the front side of the radiator that could leak air with duct tape, leaving the only access for air through the fan (the duct tape was not in contact with the cooling fins of radiator, it just created a perfect shroud). When tested with the duct tape on, it took 36 seconds to cool the car from 185 to 175 degrees (the on and off settings of the adustable thermostat that I chose). When I took the duct tape off, there was no difference - still 36 seconds, so I decided not to worry about the unshrouded area.
I am very pleased, it only comes on if I sit for a while with the engine running. I will say that it is a bit noisier than I would like, but it is acceptable.