Expansion tanks(?)
 

My '93 320CE has two expansion tanks, one visible and one hidden in the fender well. What is the purpose of the SECOND tank? If the hose to this tank was disconnected or broken, could this cause significent coolant loss?
Anziani
'93 320CE 208K
'95 E420 128K

i have the same on my 300se ,126 .The second one in the fender area is the overflow bottle for the expansion tank,and replenishes the coolant as required .

you can call it extreme overkill, its to collect any coolant that has expanded beyond the capacity of the original expansion tank. It would take some serious heat to do that.

Thanks guys. I had a coolant loss and have not been able to pin point it. Pulled the head, everything OK. I am suspicious of a one time thermostat failure. T-stat and all temp switches are being replaced. Testing the air in the coolant tank shows no combustion gases. I'm beginning to think I have a German version of "Christine". :confused:
Anziani

check the hoses near the heater valve. Also check for any tell tale signs of seepage near the coolant sensors. the 4 pin one on my car was missing its washer, I used an annealed copper washer to seal it back to the head.

Thanks. We have replaced every hose on the engine when removing the head. There are no signs of coolant loss anywhere.
Anziani