Date registered: Apr 2006
Vehicle: W111 Coupe
Location: Washington DC
Mentioned: 1 Post(s)
Quoted: 19 Post(s)
As agilot said. An easy and cheap way to clean a radiator is with muriatic acid. I pour it straight into the radiator, let it sit for half an hour and then rince well with the garden hose in reverse flow. I then repeat the procedure. Then I neutralize with baking soda. Google the procedure, it's quite well explained on the net.
Next thing is to check if the visco fan clutch works properly. when hot, at idle, try to stop the fan with a rolled newspaper. If it stops the clutch needs to be replaced.
Next is to replace the 6 or 8 blade propeller by a plastic 9 blades one. They are cheap on the net. Finally, if it still overheats, try to find a fan shroud that fits. The 230s didn't have one, the 280s had one, I don't know about the 250. If so it was specific to the 250 as the radiator dimensions of the 250 is different from both the 230 and the 280. If you can't find an original one, try many until you find one that fits satisfactorily.
Finally, but only in last resort, go with a pusher electric fan in the front. GO with a SPAL one. Google it, apparently they are the only one that really do the job as advertised. On a250 SL you can go with a 16' one, but it's tricky. You may end up with some clearance issues and the hood may not stand open properly anymore. If the car has AC there is not enough room for a fan in the front.
Don't replace the mechanical fan by an electric one. It will be worse.
Don't ask me how I know all this.