Annoying Water Leak - W124 2.8
 

Within weeks of getting my W124 300E 2.8 back on the road again with a new transmission, (amongst other things) it's developed a coolant leak and I can't seem to be able to trace it.

When I pour coolant into the expansion tank, it almost immediately pours out of where-ever the hole is. It does slow down after a while and stops pouring out when the water level is just above the coolant temperature sensor but I have seen the tank empty after the car has been sitting for a few days and the coolant has steadily dripped out.

Looking under the lower engine shield the coolant is running from behind the A/C Compressor and along the side of the oil pan and then onto the lower engine cover. The bottom of the radiator is dry, I don't suspect that. I also don't suspect the head gasket as the water doesn't seem to be coming from the passenger side (where I believe the M104's leak most often) and I had it replaced back in 2005. I can't see an obvious water leak from the top of the engine (but I've not discounted the fact that I'm looking in the wrong place).

I had the water pump replaced in november 2002 (about 60,000 miles ago). Is it time to get this replaced again or could something else be wrong?

I'd start by taking off the belly pan and seeing where it hits the ground. It doesn't sound engine related if it's doing it with the engine off.

The water hits the ground on the left (driver's side) of the engine. It's running down the side of the oil pan (about half-way down it's length) and dripping off the edge of the pan.

this sounds like a loose hose or similar, not a cracked block or anything mechanical to me.

you just have to provide yourself additional light and mirrors on a hinge or a periscope to get down there and see where it is coming from.

tom w

Sounds like the coolant is leaking form the water pump's weep hole. Check around the water pump for leaks.

Sounds like water pump to me; the location you described is almost exactly the area where it will leak when this goes. True, you recently had it replaced, but I would check it out anyway.

My first feeling was that the water pump was going bad, but I wanted suggestions from others - I seem to remember that it was dripping in a similar pattern last time I had the pump replaced. I've already taken a look at the hoses, and none of them seem to have the white crystals that I'd expect to see from a leaky hose.

Is a water pump replacement a DIY-able job? I've sucessfully tackled the replacement of the fan bearing and clutch before without too much difficulty. Going through the repair CDs I know I'm looking at 20-2100, but do I have to do 13-3200 and 20-3120 (belt tensioner removal and viscous fan clutch removal) also?

Are there any special tools I need? Some of those allen bolts look tricky to get to.

Blatent bump - Anyone know of any specific special tools to get to some of those tricky water pump allen bolts?

I have the snap-on which makes the job easy...
 

Some people were able to do it without this tool but, I bought it. I can rent it to you. If interested, send me a pm...

Good luck!