I'm a bit surprised I haven't seen more discussion on block heaters for the 320 CDI. There are a few posts where people talk about how they still start when it's cold out but here in Alaska I always have a block heater or oil pan heater on my vehicles. My new to me 2008 320 CDI had neither. After doing a bit of research I figured that heating up the 9 quarts of oil would make my engine happy with the coldest of starts. Found a 250 watt pad on Ebay for around $65.00 and then also bought a 60" roll of header wrap for around $8.00. Drove it up on ramps pulled the 4 bolts for the oil pad insulation ( the one towards the front drivers side is kind of hidden, you have to work blind with a 10mm wrench. After kind of jimmying the insulation out of there I cleaned up the oil pan as per the instructions with the pad and just stuck it on. I didn't take the pan down to bare metal like the instructions stated. With 9 quarts to heat up I wondered just how hot the pan could get. Now for the header wrap, I cut that into 6" sections and just laid them into the oil pan insulator with hi temp silicone. There are three layers in there. I took two layers and laid them on a hot clothes iron with my hand on it. It felt a little warm but not even uncomfortable. With three layers underneath the pad I'm not worried in the least about too much heat from the pad reaching the insulator. Now you just run the cord out of the hole in the front of the insulator where there is an electrical connection. Zip tie it to the lower radiator hose and run it to the passenger side of the car.Now get under the hood with a straightened wire coat hanger or something similar and run it down to where the cord is, tape the cord on and fish it up. Up top there's a small plastic piece with two clips that need to be taken out and you just run the cord under where that was to the top of the grill where you wrestle the plug through the rectangular opening the you can't really see because it's on the very top. clip that little plastic piece back in and there you go- you're cold weather ready. I'm sorry I didn't take pictures along the way, I guess I wasn't really thinking but if it helps I could post the final routing of the cord which was actually the hardest part of the whole deal. Regards, William

 

I think with the advancements in motor oil and, especially, the advancements in onboard pre-heat systems it's become less and less of an issue to have a block heater or oil pan heater. I installed both a pan and block heater (actually the block heater was standard issue) on my '98 Suburban (6.5L Diesel), but that system starts to struggle below about 25* (and I have extra glow time programmed into my ECM, too). I did something similar to what you did with the wiring, but found that the cord end would fail after just a year or two from the dangling and constant vibration (it only dangled about 2"). I then installed a covered/doored, electrical receptacle in the bumper and that has yet to fail. I wired both the block and pan heater together since neither of them really pull all that many amps.

If I was only installing one of them, I would do as you did and install the pan heater as I think that does a better job of warming things up since the pan is the lowest item and heat rises.

However, all that being said, there certainly are no downsides (regardless of how good the pre-heat system is) to adding a heater. And, the colder the temps, the more it makes sense.