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?

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Steven Harrison

1993 300E2.8 - 196K
2001 E320 4MATIC - 86K

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.

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Steven Harrison

1993 300E2.8 - 196K
2001 E320 4MATIC - 86K

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

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

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

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1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold

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.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

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.

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Steven Harrison

1993 300E2.8 - 196K
2001 E320 4MATIC - 86K

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

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Steven Harrison

1993 300E2.8 - 196K
2001 E320 4MATIC - 86K

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!

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J.H.
'86 300E