Sl280 r129

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Dec 13, 2015
Esher, Surrey
Mercedes SL 280 R129
I know this is a long shot considering the potentials. Have developed a tiny drip which has pretty much drained the water/coolant over about a two week period. The radiator light came on a couple of times which alerted me to it originally. I topped up but a few days later after a run of about 80 miles I noticed the dreaded pool of water on the garage floor. The best I could ascertain was a tiny drip coming from somewhere front nearside of engine bay seems to be high up and hidden by various parts. It was dripping into the under engine tray and then out through the center hole and onto the floor (very slow). I have ordered some fresh Mercedes coolant in anticipation of fixing or at least diagnosing. I am hoping it is a pipe or connection that needs tightening my fear is that it may be the water pump - gasket of some such thing. It is water and has the faint smell of coolant, there is no oil whatsoever everything else checks out fine.

Just asking in case anyone has had a similar experience or any advice. I expect that I will have to take lots of bits off to get to the bottom of it :(
What year - is this the straight 6 or the V6?
Buy a radiator pressure testing kit (or rent one from an auto parts store) and pressurize the cooling system. You'll find the leak. If you're seeing coolant on the ground then it could well be a bad water pump.

Not the worse job in the world.
I've just done an M104 water pump, straightforward except 2 x inaccessible ******* hex screws at the back. This guide will see you right, it took me a bit longer as I had to fight with a stripped hex bolt (Irwin bolt grips saw it out)

Mercedes-Benz W124 Water Pump Replacement | 1986-1995 E-Class | Pelican Parts DIY Maintenance Article

Whip the belt off, and check the pump. A mirror is your friend here.

Other weak points are the heater valve and underneath that the recirculation pump, doesn't sound like your problem though. These drip from the bulkhead drain, in front of the drivers door.
Straight six (1994)

Many thanks
I think the head gasket is a common problem on the M104?
I had this exact same problem on my Dad's 1995 Sl320. Water dripped nearside slowly when running. Turned out to be the water pump. Bit awkward to do with the position of a couple of the bolts, the use of a universal joint on a socket will do it. The water pump has no gasket, but a small rubber seal that fits in.
I think I have pictures somewhere of my Dad and I doing it.

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