What's the story with the M104 water pumps?

[Greg in Oz]

I have just recently replaced the water pump on my father's '93 E320 coupe (M104). The job was much easier than it looked (and I was lead to believe it would be). It appears it would be a more difficult job on our M103 (never had to do it yet). I also replaced the belt tensioner, tensioner damper and belt as a precautionary measure since I had them all removed.

When ordering the pump, I was asked whether or not the engine had an oil cooler. The oil cooler versions of the pump have an additional pipe at the rear which this car does not. At the time, I was informed that the pump I needed, a 104 200 2801 was no longer available and that I would have to use a 104 200 3301 and plug the extra port. The only problem was, no one could explain to me how this should be done. Eventually, a 104 200 2801 pump was located, so I did not have to deal with the problem.

This leaves the question as to just how does one deal with the extra port on the 104 200 3301 pump? Looking at one, a logical solution would be a cover plate retained by two screws into the tapped holes (provided in the pump). The plate would retain an O-ring in the groove around the hole to form a seal. I am told such a cover plate is not available so therefore is presumably not the solution.

Anyone know the answer to this one?

[Paulwho]

A simple expansion plug (freeze plug) is tapped into the hole, nothing fancy. Supplied here through MBUSA

[Greg in Oz]

Thanks Paulwho,

I guess that is a solution. I'm pleased I managed to find the correct pump that did not need this mod, though. These cars have enough potential places for coolant to leak without adding more! Most repairs to my family's and my MBs involve the cooling system in one way or another. Water pumps, radiators, expansion reservoirs, thermostats, temperature switches, O-rings and fittings, hoses, heater valves and I guess head gaskets since it seems to be corrosion that affects them. Yes, I do use genuine MB coolant. It finds its way out everywhere! You cannot afford to have faulty cooling systems in the Aussie summer temperatures we have at the moment.