nj300se, if there is no sign of leaking coolant from the water pump weep hole then the leak is elsewhere. If were you I would drive the car onto a set of ramps, remove the encapsulation pan under the engine , wipe everything dry, then start the engine with the hood open and look closely for the leak ... first from above the engine, then from underneath the engine until you locate the source.

At your earliest convenience I recommend replacing the plastic thermostat housing. It's possible it has developed a hairline crack that leaks coolant. Also, closely inspect the upper radiator hose connection. The plastic connectors on old Behr radiators are not reinforced and develop circumferential cracks with age. I had one break off completely ... fortunately my wife was in a parking lot when she noticed coolant leaking from the engine compartment. Having the upper radiator hose connector fail at high speed could cause major problems. If the hose connection is leaking there should be a white residue from dried coolant ... assuming you have MB coolant in your radiator. The proper fix is to replace the radiator.

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Fred Hoelzle

in my case, the leak was coming from in-between the pump and the block. the seal in-between had deteriroated with time....

go to autozone, get a telescopic mirror for like $2. they are very helpful for diagnosing problems with these cars as they have a lot of dark, hard to see spots....it looks like a pen with a round mirror on the top.....

check the hoses as mentioned above....

good luck

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1993 300E, 2.8 M104 .....

Thanks again guys. I haven't had a chance to pinpoint it (its a garage queen anyway) but I 'think' it is going to be the gasket like latief experienced. If I end up having to do the gasket, I'll just do the pump, t-stat and the housing as suggested. Makes sense. Today, there is some good sunlight, so I think I'll stop at AutoZone and pick up one of those mirrors. That will come in handy for this and other problems I'm sure.

I'll keep you posted with what I find!

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Not sure if you have resolved your issue or not, but on my 300SEL (same engine as yours) had a coolant leak (until today) it was the very short hose that runs from the head to the thermostat area that was leaking. I put on new clamps... hopefully it will resolve the issue, since the what appears to be an easy hose to replace is a pain in the neck to replace.

I had a major loss of coolant on my 91 300SE with 81K miles and it was the water pump. Mercedes dealer wanted $3K and said it was a head gasket. I had the water pump replaced about 2 and half years ago and have had no problems since! I also got a new radiatior and thermostat at the same time. Thanks also to those on this board who pointed me in the right direction!

Just an update - going to pick her up tonight, I'm really happy that I have a good indy MB shop nearby.

It was the waterpump, so out it went along with the upper and lower hoses, t-stat, t-stat housing (metal) and I figured what the heck and had them replace the radiator with a new Behr with the metal reinforcements. So, it cost a decent amount, but all that stuff was weighing on my mind anyway - might as well do it now! Original radiator and original everything else actually too!

So, thanks again to all the people who helped me out. I like knowing a little about what I'm talking about with the mechanic. Thanks!

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