Thanks again for your help, everyone. I'm amazed how much support there is here!

Here's what I've been up to, followed by one last question.

The new (all-metal) radiator arrived today, so I set about putting it in.

First, I finished replacing the water pump (the project that started this all). I had a hair-raising moment when I broke off one of the bolts I was using to attach it to the "housing" (the last thing between the water pump and the engine block). I was using the Haynes manual, which seemed to say to attach the water pump with 33 Nm of torque. I started thinking things were feeling a little weird around 17 Nm, and then just as I was deciding to stop at that point, one of the heads broke off. I think the Haynes manual was actually specifying the torque to attach the "housing" (whatever that is) to the main block; the Mercedes shop manual called for only 10 Nm of torque. I should have double-checked before I started!

Fortunately, when I took the water pump back off, a little bit of the bolt was sticking out and I was able to grab it with vice grips and twist it out. I was not looking forward to getting the shop to drill it out (my first thought, which they quoted at $600), or drilling it out myself (my second thought), or making another trip to the parts shop to replace the housing (my third thought).

The rest went smoothly. I went and bought new bolts to replace the tired old ones holding on the water pump and the fan. Then I had no trouble attaching either part. For the fan, I ended up using just a long 10 mm crescent wrench. I got a feel for the right torque (20-25 Nm) by turning the crescent wrench against my torque wrench untll it "popped", and then I tightened the fan bolts to what felt like the right amount. It was a lot less torque than they had originally been attached with, and with the new bolts and careful wrenching, I was able to avoid stripping anything. At this amount of torque, I could keep the fan from turning just by holding the pulley with my other hand.

Then, the radiator installation was pretty smooth, except . . . the oil cooler fittings on the new radiator seem to extend about 1/2 inch less back into the engine compartment than the ones on the original radiator. Unfortunately, the rubber hose from the transmission cooling line on the passenger side was just long enough to reach the old radiator, so now it's 1/2 inch too short to reach the new radiator. It's pretty excruciating to be so close and not able to finish the job yet. I went to Kragen and asked for a longer hose, and they said to check with Mercedes. I was surprised, because I thought this would be a pretty standardized part. I'll call the Mercedes dealership tomorrow, but if they only have hoses that are the same length, it's not going to do me much good.

Does anyone know where I should look for a custom-length rubber hose for the transmission oil cooler on short notice? I need to put it in tomorrow.

Thanks again.