On an '82 mercedes 300SD, the water pump was replaced before I bought
the car last year. After I flushed the system it developed a very small
leak from the water pump and the local mechanic said I needed a new
It only leaked in the morning when the sun was warming up the car with
the engine off and then it would stop leaking and the change in
temperature stopped. Else when I started the car it leaked a little as
the engine warmed up and then it stops leaking.
I got a new water pump and had about half the coolont replaced and
after 1 month it is doing the same thing again. It seems like it is
building up too much presuure in the engine block when the temperature
increases with the engine off. Is there supposed to be a path for water
back pressure in the engine block to go back into the radiator when the
engine is just sitting there turned off and is getting heated just from
the sun shining or air temperature increases?
Is it possible a small amount of citric acid flush is still in the
system and eating up the water pumps? I flushed it for maybe 45 minutes
because it was hard to get engine block coolant to circulate very much
when doing a flush.