Hi
I live in Singapore and I have a 92 230E (124). I have been changing the fuel pump on the average once a year which I think is not normal.

Recently I have been experiencing a loud hissing sound coming from the fuel pump after prolonged driving - 100km or more. The sound goes off by the next day. So it is temporary hissing sound and not an indication that the pump is faulty. I was told by a colleague that the pump could be overheating as not enough fuel is going into the pump to keep it cool. The mechanic has confirmed that it is due to overheating of the fuel pump. I am looking into replacing the fuel pump, fuel filter and flushing the fuel lines. Could it be due to the car being old and there could be contamination of the fuel tank. My mechanic feels the flushing of the fuel tank may not be necessary since the contaminants should not bypass the fuel filter. He will examine the fuel filter to confirm if it could be due to high contamination level of the fuel tank.

I would like to have your views. Do you think overheating is a likely cause and what could be causing it other than the reasons mentioned above,