Well I need to let everyone know what's happened so far (pardon the length). I'd like to close the thread at this point by saying everything is back to normal, but I don't think that's the case just yet.
I have been driving the 300E (keeping a close eye on temp)while waiting on my new thermostat to arrive. Careful driving has kept the temp down and everything has been ok, but my luck ran out last Wednesday evening.
I had stopped at an ATM for cash when suddenly there was a loud pop and an explosion of steam from under the hood. Temp had been a little high, but not bad because I had just stopped. I quickly shut the car off and pushed it off to the side to try and determine what had happened -- all the while praying for a busted hose. No such luck. I had a five inch split in the radiator below the upper outlet in the plastic side piece. Why didn't I order that radiator too!! Now I'm wondering if I've damaged the car.
Well, I got the car home and read everything in the forum on radiators. Even with the help of the forum's past radiator topics, I still couldn't decide what to get, Behr or Nissen. I was just plain sick with what had happened to the car anyway, so I put the decision off until Thursday.
Thursday I decided on the Nissen (taking Fastlane Phil's advice), and place my order (I've covered this under another post). I received and replaced the radiator and thermostat yesterday, flushed, and added 50/50 Prestone antifreeze. By the way, this stuff is called Prestone 5/150 Extended Life; and is silicate and phosphate fee; and meets DaimlerChrysler MS7170, MS9769 (whatever that means); and it's orange!!!
After a couple of short test drives around the block, I drove the car hard for an hour or so yesterday evening. While on the highway, temp stays around 87C. When stopped, temp stays low for a couple of minutes then slowly starts to creep up. When it gets just above the unmarked line between 80C and 120C on the gauge (what is the marking anyway? Does anyone know?), I hear the auxiliary fans kick on. The temp temp then slowly falls back down to close to the same as it is when running on the highway. Sounds normal? I think so from what I've heard here and from what my owner's manual states -- I really hate to see such wide swings though. Maybe I'm just gun shy now, and I really hadn't paid a lot of attention to how the cooling system acted until I had this overheating thing.
Anyway, there's more. I figured I still needed to test for proper operation of the aux fans, just for piece of mind. I popped the hood this morning to install an new pressure cap on the coolant reservoir (also for piece of mind), and for some reason decided to look at the fuses. When I removed the cover the first thing I noticed was that the card that tells what's what on the box cover was charred! The fuse in position "D" was the culprit. It looked like maybe the element had cracked but still made contact intermittently (causing heat). I dunno. I checked what I could read of the card (does anyone know if I can buy the card as it is ruined?) and saw that fuse "D" is the auxiliary fan!
So anyway, that's where I am now. I haven't replaced the fuse yet and I need to check some things I suppose. Any advice guys?
1990 300E (parked again)