This afternoon I looked at a used 1991 420SEL. Only 125k in the clock. Car checks out ok, but I noticed that the fluid in the washer reservoir was dirty. I touched the water and it DID NOT feel oily (did not look oily either). Just dirty and it looks like there were little black blugs (or "specks" not sure which one).

I am planning on having a thorough pre-purchase inspection. But just preliminarily, is there some significance to this finding?

I understand that oily fluid in the coolant return reservoir usually means a bad headgasket (or some other horribly thing ). But I am not sure what significance to attach tot he dirty windshiled washer reservoir.

Your input will be greatly appreciated.

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Back to back to back National Championships (we hope!)

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Current Benzes

1989 300TE "Alice"
1990 300CE "Sam Spade"
1991 300CE "Beowulf" RIP (06.1991 - 10.10.2007)
1998 E320 "Orson"
2002 C320 Wagon "Molly Fox"

Res non semper sunt quae esse videntur

My Gallery

Not in this weather!

My guess would be the PO put in tap water instead of the washer fluid blue stuff and after about 1 month or so the bugs and algae take over. The black stuff is probably mold. Smell it and then smell a jug of the blue washer stuff and compare.

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles

just to chime in, i am very opposed to using the "blue stuff" in my own mercedes or recommending it to customers of mine, the majority of the time when systems do contain this type of cleaner alot of them tend to become clogged, mercedes sells both a soap for summer weather or for climates that dont have freezing temperatures, and a soap that will protect the washer bottle during freezing weather, i suggest using these. here in southern california we do not need to add solvent to the bottle that will prevent freezing so all i use is the summer version, it will not crystalize as does the blue type causing clogs.

DTF & Carson, thanks for the replies. In my previous Benzes I have used the factory summer wash. Over the long it is cheaper than replacing those silly little nozzles on the hood of the car.

So, you guys don;t think that the dirty water is anything to worry about? Like I said, there is no oily residue. It would be a different story if the dirty water/oily water was in the radiator overflow tank, then I'd worry.

Thanks...and anyone else, please feel free to chime in.

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Current Benzes

1989 300TE "Alice"
1990 300CE "Sam Spade"
1991 300CE "Beowulf" RIP (06.1991 - 10.10.2007)
1998 E320 "Orson"
2002 C320 Wagon "Molly Fox"

Res non semper sunt quae esse videntur

My Gallery

Not in this weather!

i don't think i would worry about it, i would flush it really well and monitor it,
usually what i have seen is the little thermostat on the heater coil will leak and fill the bottle with coolant, even on severe headgaskets where the coolant reservoir is severly contaminated with oil i have never seen oil in the washer bottle. i think as previously stated the customer must have put in plain water with out any cleaner.

Yup, it's probably algae. I used to keep only water in mine and had these black spots develop. Just get a brush and scrub them off. I certainly wouldn't let it hold up the purchase.

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95 E320 Cabriolet, 159K