I have coolant leaking down the oil pan on M103 engine in vicinity of oil drain plug.

I can not see the weep hole on the waterpump. I am assuming the coolant pump is leaking.

Is the coolant leak I describe the sympton of a coolant pump leaking from the weep hole?

I have posted this response twice in the last week

Did this job myself last week on my W124 M103 260e. Water pump was O.K. just a leak from the bottom.
What a barsteward of a job to replace a $ 3.00 O ring. The Aircon hoses are in the way of the rear bolts of the pump.
While removing the components to get at the pump I rocked the water pump pulley back and forwards to determine whether or not the pump front bearing was O.K. The rocking backwards and forwards of the pump exacerbated the O ring leak and it was quite easy to see coolant dripping out from the bottom area of the pump and not the bearing assemblies. The rubber O ring between block and pump body flat, hard and leaking


Items removed to facilitate job: Fan shroud, fan and clutch, fan and power steering pulleys, Dipstick and tube removed, belt tensioner, power steering moved out of the way, removed distributor to get at bolt holding heating tube to block, first two injectors and lines, moved IACV out of the way, radiator hoses.
Time taken to complete entire job 8 hours - including time to look for dropped bolts hidden in inaccessible locations

New items: O ring for pump body, O ring for heater tube, new bypass hose between block and thermostat housing, lower radiator hose.

Ivanerrol recommends purchasing a flexible extension - extremely handy.

I'm a member of that team.

Helpful and interesting reply. I will try to inspect the location where the coolant is leaking from tomorrow.

Once you had the whole thing apart did you consider replacing pump due to the labor involved?

Pump was O.K. and had already been replaced previously by P.O. My car has only done 150Ks (kilometers - 100K miles)

Next time I need to do this job, I estimate it to take less than 4 hours.

The real pain is that less than two months ago I replaced the belt tensioner. I should have done this job then. However two months ago we weren't getting 118 degree F days or three days in a row over 110 degree F in Melbourne Australia

If your pump is suss I would replace it.

Ivanerrol, Nice sanitary looking engine & bay. Looks like someone else is as obsessive as I am. Is that your doing, or did the PO keep after it? Only thing left is to powder coat the valve cover next time it's off. Sweet!

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

Ron, you can buy a small inspection mirror on a telescoping handle and check the weep hole.
But, actually it doesn't matter, the pump has to come off either way. When you get it off you will easily tell if coolant has been leaking out the weep hole - it leaves plenty of residue.
I'm on my 4th water pump on my 300SE (18 years) and I managed to replace it last month removing only the pulleys and the tensioner, and rotating the steering pump a bit. But it's pretty tough to get those rear bolts.

DG

My inspection mirror are to big to get under the coolant pump. I'll get a smaller one.

I'd put the pressure tester on it when it cools down and leave it on all night and check in the morning.

Coolant pump in photo is spare I will most likely use. I put a yellow line where I think the one on car is leaking. It's not leaking from the weep hole and I don't think it's leaking at o-ring seal, but not sure.

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Agree, but the coolant areas look a lot more corroded than I would expect using the right coolant and water ratio. Could that be?

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Prost!

You would have a reasonable assumption there. The P.O. (A Honda Mechanic) had put the cheapest green coolant you could buy at the supermarket in. The leak was insidious which required daily top up with distilled water. I didn't want to put expensive MB stuff until in I sourced the leak. I have cleaned up all that corrosion with a light application of wet and dry.

I went ahead and removed coolant pump and tensioner. Everything came out with no problems. Hopefully it will go back together as easily.

I'm not going to bother with new parts. My spare pump seems fine, bearing is much smoother than the bearing in the one removed.

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^inside of the block looks great

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Thanks. This motor has been very well cared for. It's such a good motor, that when my 1992 300E was hit from behind and totaled I removed the engine and transmission as a unit and put them in my 1992 300TE. The motor and transmission have only been in the wagon about 3 or 4 months.

I put a new front crankshaft seal in the motor earlier this week.

compartment looks great!
How on earth did you get the tensior and pump out without touching the ps pump?
I'm trying to do it myself right now...have the same problem.
can't seem to break the pulley bolts. advice?
well done.
cam

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1987 300e W124 M103 My baby.

I moved the power steering pump out of the way.

I posted some instructions for you in the thread you started.