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1995 C280 (165K mi)
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Discussion Starter #1 (Edited)
Hi all,

Today morning I had a few drops of coolant dripping out of what seems to be the bottom corner nut of the water pump. Could this be a sign of something terrible to come?

Recently:

  • Yesterday night we had a sudden snap (the start) of winter weather. We hit 32 degs for about an hour or two and this morning I see the coolant on the road.
  • Two weeks ago I had my emissions test done where the idiot tech had to run it twice and made my car race at ~2500 rpms in park for about 4 mins each time.
What do you guys think may be the issue and any repair recommends? I have plenty of coolant in the system, no over heating. I believe it is simple contraction of either the screws, gasket, back plate of the motor housing, etc.
 

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'01-E320 & 02-ST2
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First I have to say I like the coat of arms...and the sig. :D

There is a little weep hole along the shaft of the WP housing. It's there to let you know when the inner seal has started to go. (It also prevents pressure from building up, seizing the bearing and catastrophic failure.) My guess is that is the place from which the coolant is actually escaping. At 130K miles that is decent life for the WP, too. If you don't find a leak in a hose nearby, that's almost certainly it.

It's not an awful DIY, just getting to it. Plan on draining the block and refilling with fresh spec coolant, too. If you take it in, $600-800 depending on the shop.

Take care and enjoy the ride,
Greg
 

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1995 C280 (165K mi)
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Discussion Starter #3 (Edited)
Thank you. I like the Coat of Armor, looks striking. And as for the signature, well, my MB has outlived many women. I give about 5000-7000mi/woman!

Now for the question, what happens if the weeping stops and I see no more leaking? Do I just forget about it or do I need to replace the pump ASAP?
 

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95 c220
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33 Posts
Thank you. I like the Coat of Armor, looks striking. And as for the signature, well, my MB has outlived many women. I give about 5000-7000mi/woman!

Now for the question, what happens if the weeping stops and I see no more leaking? Do I just forget about it or do I need to replace the pump ASAP?
Mine went at about 62,000. 95 c220 Grab the fan mount and see if there is any up and down movement. Mine was flopping around squealing the belt and starting to run hot. Do yourself a favor and change it even if the weep leak stops. The hardest part is the big fan nut. (left hand thread).:thumbsup:
 

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1997 E320, 1997 S320
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mine said goodbye at around same mileage also. do yourself a favor and replace it before it gets below freezing. it is labor intensive job, i know it took me almost all day, but it was the most difficult job i had done so far at the time. if i had to repeat the process would probably take me 4 hr max. considering the age/mileage i recomend replacing upper/lower/bypass hoses, thermostat, and serpentine belt since you will have the old one out. use zerex g-05 coolant or mb labeled one. also don't get a very cheap water pump from ebay. i think autohaus has graf pump for good price. all parts should cost you a little over $200. good luck, and if you have a camera try to snap a few pics, i don't think anyone has done a diy article regarding m104 water pump yet.
 

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'01-E320 & 02-ST2
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When I posted it was from a smartphone, so I didn't notice you had the 104. That makes it a bit easier since the process is like the 124 and there is a ton of stuff out there on that. Here's a link to the basic process for the water pump: http://w124-zone.com/downloads/MB CD/W124/w124CD1/Program/Engine/104/20-2100.pdf and here's a bunch of info related to the 104 in the 124. Much will be the same, always a good starting point: Mercedes Benz Model 124 - M104 Maintenance Manuals

Have fun with it. As tirona suggests, it's just labor, but pay attention as you go along. Diagrams and pictures are invaluable if you get stuck and do set aside a full day; take breaks if you get frustrated. Even if you need to buy some tools, you'll still be lots of money ahead.

I also agree on hose replacement; I guess I'd figured at that mileage you'd have already done them. Be sure to flush/clean out the recovery tank, too, scum can build up in there.
 

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1995 C280 (165K mi)
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Discussion Starter #7
Thank you guys very much. I guess I should take this up soon. There is indeed little DIY on this matter. But thank you for listing some links and diagrams to assist me. I will take pics if I DIY it.

I gotta say, looks like a lot of work and may take me a whole day!
 

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Before you change the water pump, unless of course you can see it leaking, why don't you have the cooling system pressure tested. Do it both hot and cold. A lot easier to find the leak.
 

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1995 C280 (165K mi)
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Discussion Starter #9
marvin, thanks. i didn't even think of that. i should look into pressure testing it but i have no equipment for that.

there has been no seeping of coolant since. maybe it self repaired itself!
 

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German Stuff
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marvin, thanks. i didn't even think of that. i should look into pressure testing it but i have no equipment for that.

there has been no seeping of coolant since. maybe it self repaired itself!
I think that makes a better case for pressure testing it. I had a 540i that would evacuate some of it's coolant when I would park just for a little while after turning it off. I'd top up once a week and it would do the same thing. Had it pressure tested, there was a tiny little hairline crack along the molding line of my expansion tank. When cold, the coolant didn't reach it. But, when it was at operating temp after driving, and the engine was turned off, it would fill into the reservoir and drip out until it was below the crack.

Never would have found that without the pressure test. It was literally invisible, I couldn't even see the crack when my shop removed the tank and gave it to me, but I watched it drip out of it with my own eyes.

Cooling systems aren't something to mess around with.
 

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1995 C280 (165K mi)
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Discussion Starter #11
good point E36. i think i need to watch it a few more days and possibly do a pressure test. can a pressure test hasten a possible fracture or cause other damage? Isn't the cooling system under pressure when parked after a long drive? so any leaks should show up then or soon after. and it hasn't yet.
 

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1998 C230 53K
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The funny thing about a leaking seal in the WP is that it might not leak when hot and under pressure but only when the car sits awhile. When the WP on my W201 started to leak I didn't see anything at work or the next morning but if I parked it all weekend there would be a small puddle. It's counterintuitive but I've seen it on other cars as well.

The 190e got totaled before I got around to replacing the WP...
 

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1995 C280 (165K mi)
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Discussion Starter #13
wtf.

if it doesn't leak anymore or overheat i will just leave it alone. no need to fiddle with the pump if it is ok now and the leak was temporary, happened once for an unknown reason.
 

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1987 300e (W124) - 223K miles, 1995 C280 (W202) - 250K miles Sold
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My question is along these lines, so I guess this is as good a thread as any to ask it...

I'm replacing the expansion tank (which some people incorrectly call the "overflow tank") and cap because I know it was leaking. I could see coolant squirting out of a slit in the side of the white plastic part. No way I could be wrong about that!

There are 3 hoses connected to this tank. The large one at the bottom connects to the heater (indirectly, of course). The smaller one on top - NOT at the filler neck - connects to the thermostat housing. The smaller one on top that sticks out from the filler neck goes to to what the EPC labels the "overflow tank". That little hose is very brittle. Part of it broke off, just before passing into the compartment near the firewall where there are some control modules, etc.

So...where is this "overflow tank" located? Will it be possible to replace the hose all the way from the expansion tank to the overflow tank without dismantling everything in the engine compartment? If I don't replace all the hose and the coolant level in the expansion tank maxes out, could a break in this hose let coolant escape?

I hope someone can advise me; I've found nothing specific about this by searching the forums here.
 

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1987 300e (W124) - 223K miles, 1995 C280 (W202) - 250K miles Sold
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FWIW, the MB part number of the "Tank - Overflow" is 202 500 00 49 and the hose is supposed to be 830mm of #230 476 87 26 hose tubing. MB Part number of the Tank - Expansion that I'm replacing is 202 500 06 69, with cap #210 501 03 15 (replaced by #210 501 05 15?) replacing the original tank #202 500 02 49(old one that leaks).

For now, I'm using a short piece of 1/4" ID heater-type hose and a brass connector to replace the crumbly, brittle part of the hose that runs from the filler neck to the old hose where it broke off...about 8". If I do have replace the rest of the hose, I'd like to replace it with a single piece and avoid the splice...
 
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