My vehicle is a Sierra P/U with the 4.3L engine. Over the past couple of winters here in NW Indiana I've ran with the radiator 85% blocked. My crude, but effective technique is to put cardboard between the the A/C coils and the radiator because of the ease of adding and removing same. This summer I ran with the radiator 80% blocked without any problems. I'm considering using a 90-95% blocking of the radiator for the winter. I'd like to hear from folks in the northern climes about their blocking techniques, materials used, tips and tricks.
I had the radiator in my 98 Sierra with the 5.7 L V-8 95% blocked with no problems. The a/c was a little weak (but still usable) on 100 degree days. I ended up ripping it out because I was going on a road trip on a very hot day and I wanted the A/C (and transmission cooler) to be at its best. I'll probably put it back in sometime in the next month or so.
I ran 100% block on my 2002 Sierra 5.3 with the same technique as you, having cardboard (actually I used corrugated plastic, similar but weather-resistant) wedged between the engine's radiator and the A/C stuff. I tried it for a while in varied weather, ranging from warm to cold. It was fine.
I eventually made a nice cover for the front of the grille to force the air around the truck instead of letting it past the grille at all. It worked great except my transmission temperature went way up, so I eventually took it off. I think this winter I'm going to put the coroplast back in front of the radiator.
What distances are you guys driving? I had a 24 mile commute each way to work before I moved to New Mexico and when I tried a 50% block between the AC and radiator my mechanical fan clutch started stiffening up all the time and the losses from a fan pulling against a blocked radiator as hard as it could ruined my mileage.
38 miles to work, 40% freeway (set the cruise control at 65-70mph) and the rest a combination of town and country roads. I don't know how to tell if my fan (also a clutch fan) is running all the time, but my fuel economy was not measurably affected. My temperature never rose above normal, and that temperature gauge is quite dependable.
If it is a good clutch, which I imagine in a 2002 it is, you'd hear it. The Durango's fan has a super duty clutch on it from the factory and when that thing stiffens up you know it. With it at full hold I can't rev past 3000 without the belt starting to slip, and that's with a good belt! It only really does that around town with the ac on or when I'm off road though.
I tried to rev it up with the hood open while the clutch was hot like that and I couldn't do it. The level of heat coming from that system is unbearable.
ne other suggestion I have is to throw a piece of cardboard over the engine to act as an engine "snuggie". The idea is to help insulate the engine aiding in quicker warm-ups, and preserve engine heat a bit longer when you're running errands with multiple stops.
I have no proof that this actually helps. but when it's -20 outside, it can't hurt.