Overheating 300cd
 

Hi, earlier this year I bought an 82 300cd(my first mercedes)with 170K + on the odometer(not working). The car ran great for about 3 months until it overheated on a very warm summer day. I parked it and tried to find the problem. The Radiator had a cold spot at temp. so I put a new one in. This didn't solve the problem as after about 50 miles of driving on a cold day it got warm(hot) again so I parked it again. Yesterday I deciced to crank it up and see if I could spot something, I did. After letting it warm up a bit I pulled the oil fill cap and noticed steam coming out, not good. However there doesn't seem to be any water in the oil pan. What bothers me is the motor runs really good even when it was overheating. I don't know alot about mercedes diesels so I'm not sure what to do now :confused:. Is this a head gasket issue or a possible cracked head, is there a way to tell which without tearing the motor down? Or do I need to roll up my sleeves and tear off the top end(I am capable). Also if it's a cracked head are these heads repairable. I really like this car and would like to get it back on the road so any help would be much appreciated. Thanks Moconn.

water pump is gone
 

Replace the water pump. It is an easy DIY job and will cost about $50 for the pump. You should find plenty of threads that describe how to replace.

I had a similiar experience...although I did not have steam from the oil filler cap. :eek:

Are you sure it was steam (water vapor) and not oil mist? The oil mist in the 'blowby' gases are collected at the air filter and returned to the crankcase. The oil mist looks somewhat like steam, and you can see it if you open the oil filler cap.

Agreed, and over heating, to what temp? Or did you hear things you should not have? Anyway, a new thermostat is the cheapest thing to replace.
What color is the oil when looking in the cam cover? Normal black color, OK, a milky light brown color = not good, oil and water mixing.
Water pumps USUALLY let you know they need replacing by leaking fluid at the weep hole on the pump itself.

before you go tearing into it, see if you can get a pressure tester and test the system. Dont forget the cap, its a common issue and easily overlooked. If there is a pressure leak, the coolant will boil. If there is no pressure leak then there is an obstruction or no movement, check the t-stat to see if it is opening or just replace it, then all thats left is the pump.