I changed a water pump on my 1993 400E and found some additional work was required that I did not contemplate. In order to get one of the pump bolts out, I had to remove the crankshaft damper. There is one bolt that is about 3 inches long and the damper interferes with pulling the bolt completely out.

I am told that most Mercedes have either a hole in the damper that allows you to remove the water pump bolts, or the damper can be "walked" off the crankshaft hub after loosening the five or six smaller bolts that hold the damper to the crankshaft hub.

But on my 400E, the only way to get the damper off was to remove the big bolt in the center that goes into the crankshaft (I think it took a 27 mm socket). This bolt is torqued to several hundred foot-pounds and I was told that loosening it would create a high chance that the crank seal could leak unless the hub was extracted and the seal was replaced. This takes additional time and a special tool to extract the hub and install the seal. You may also have to heat the hub up with a torch to expand it so it will slip back onto the crank when you reinstall it. I think the manual calls for this.

In any case, in order to remove the crank bolt, you will have to inhibit the crank from turning as you loosen and tighten the bolt. The option is to remove the starter and insert a special tool that locks the crank, or some people just pull one of the bolts out of the torque converter and insert a homemade hardened bolt and sleeve to keep the crank from turning during the loosening and tightening process. The removal of the damper might be the reason for the high labor charges.

Of course, the dealer will always be the highest quote you can get, so I'm sure you could find an independent Mercedes repair shop to beat that price.

I think it would take a crystal ball to determine how long your leaking pump will last, but keep in mind that if you keep adding just water, it may dilute your anti-freeze/water mixture down to the point that the cooling system would be adversely affected. Some people also contend that anti-freeze provides lubrication for the pump, although I'm not really sure this is true.

Are you sure it's the pump and not just a hose that's leaking? My pump had about 200,000 miles on it and it wasn't even leaking. I just changed it because I thought it must have been worn out with that many miles.

If the pump is original, there should be a drain line about a foot long that goes from the weep hole into a small recovery tank. I can't remember exactly what it looked like, but I was told that it was not necessary and no one ever replaces this hard brittle plastic line when they replace the pump. Is the pump leaking from this line?

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles