616 engine water pump replacement
 

I live in the USA but own a 1983 Mercedes motorhome in the UK built on a 1983/4 307d chassis with a 616 engine. When I left it over Xmas the water pump was leaking. I will need to replace it when I return to it in May. Can anyone with experience give me advice on any obstacles I may encounter. I ordered a new pump from Europa and according to their parts info, my engine requires the pump with the single center bolt holding the fan assembly to the pump. I know I need to put a short piece of rod through the pump housing and shaft to hold the pump in position while removing the fan attachment bolt Does anyone know the size of the head on that center bolt? Is it easy to get the piece of rod in position? Any special tools or double jointed limbs I should acquire before crossing the pond? As an aside, why would a company which seems to have good engineering sense over all come up with the idea of attaching a fan to a pump with a single center bolt and no pins to hold the fan and pulley in position??? It strikes me to be a problem just waiting to happen.

I cant speak for the 616 engine, but I have done a waterpump or two on the 617 engne (one more cylinder).

Remove fan shroud
Loosen alternator and Power steering pump so you can loosen the belts
10MM closed end wrench for the bolts on the fan (you may need to grind it)
10MM rachet for the waterpump, I think its 5 bolts.
Tighten them evenly
Re tighten the belts, but not too tight!

Its a pretty simple job.

This is a piece of cake job. Everything is intuitively obvious.

You said you saw the leak on Christmas. What was the temperature when you saw it? If it was freezing or colder and it is not leaking now, don't worry about it. This is a cold weather leak because the shaft is slightly contracting. Unless you stay in weather this cold much of the year, just live with it, it will leak very infrequently.

Good luck,

Thanks for all the advice. It wasn't that cold when it was leaking and it was a steady flow when the engine was running. The pump also squealed periodically so I need to do it. However, the "bizzare' part that someone mentioned is what concerns me. The pump is not like the pump on the 617 I have here in the US. There is no flat plate at the front with bolt holes on it. There is just a large bolt hole in the middle of the pump shaft to which the fan and pulley attach. You have to run a pin through the shaft at the motor end of the pump (through large weep holes essentially) because otherwise the whole pump shaft will turn when you attempt to tighten the fan and pulley. I'm assuming that this large center bolt is quite a bit bigger than 10mm since it holds everthing together on the front of the pump.

Here's an update on the waterpump replacement on a 616 engine on a 1983 307d. It is quite unlike the waterpumps on 616's in 240d's. There is a fan clutch with a large bolt which comes out of the back of the clutch with no head of the bolt coming out the front of the clutch. (the fan bolts to the outside of the clutch) This bolt screws directly into the shaft in the center of the water pump after passing through the pulley which is sandwiched between the clutch and pump. The shaft of the pump must be held by a pin of some kind which passes through the top weep hole, through a hole in pump shaft and out the bottom weep hole. The bolt coming out of the fan clutch has two flat sides. These flat sides are matched to a hole in the pulley which also has two flat sides. The only way to remove the bolt is to turn the pulley which by virtue of the flattened sides of the bolt and pulley, turns the bolt out of the pump. The pulley has a piece of quarter inch flat steel welded to the front of it. This steel piece has two flat sides resulting in the necessity of a thin wrench with the capability of being opened to about 3 inches being used to unscrew the pulley. A standard pipe wrench would be ideal if it could fit into the narrow quarter inch space between the fan clutch and the pulley. They won't fit. I ended up using an old british pipe wrench called a footprint wrench to unscrew the pulley. A big set of water pump pliers might also do it but I didn't have any available. It took me quite a while to figure this out and I got some help from a mechanic at a UK Mercedes truck dealer. I was quite puzzled initially by the fact that the bolt that threads into the pump was not visible on the front of the fan clutch. It was only after reaching behind the clutch with my fingers that I was able to feel the flat faces on the front of the pulley to which the wrench must attach.
The system is functional and once understood is not that difficult to work on. However, I have never seen another attachment system like this on any other water pump. Why Mercedes chose such on odd mechanism on a few years production of 616 truck engines is a puzzle to me.