Mystery coolant leak.
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From: Phoenix
222 S-65
Mystery coolant leak.
Guys... My 2015 S-65 is dripping blue coolant from the driver’s side frame rail while running.
No coolant leaks under hood.
No coolant hoses I can see on driver’s side.
Charge coolant is pink so not that.
Thoughts?
No coolant leaks under hood.
No coolant hoses I can see on driver’s side.
Charge coolant is pink so not that.
Thoughts?
Last edited by JohnLane; Feb 1, 2026 at 06:55 PM.
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From: Fleriduh
W212 E63S Wagon - GSL580 - E63 - E350 - C300
Engine rear to firewall - there are hoses....they break (mine did). Not sure about your engine specifically but my coolant temp sensor was back there as well...and leaking.
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From: Phoenix
222 S-65
Coolant is a darker color than washer fluid and it tastes sweet. I compared on paper towels.
Trans oil is blue but doesn’t feel like this on fingers.
Also.... drips when running.
No coolant lines on driver’s side. Zero signs of a leak at the engine. No scent of coolant under the hood. I can smell hot coolant every time under the hood.
Trans oil is blue but doesn’t feel like this on fingers.
Also.... drips when running.
No coolant lines on driver’s side. Zero signs of a leak at the engine. No scent of coolant under the hood. I can smell hot coolant every time under the hood.
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From: Phoenix
222 S-65
I have it on the hoist and am clearly missing something.
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Thread Starter
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From: Phoenix
222 S-65
Thread Starter
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Joined: Feb 2012
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From: Phoenix
222 S-65
Zero leaks on engine. The Goo that comes out of engine mounts is a very different color and not coming from mounts that I could clearly see with the car on the hoist and all plastic removed.
This one is quite the head scratcher.
This one is quite the head scratcher.
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From: Pacific Northwest
2001 S600 V12 Sold, 2011 Jaguar XFR Sold, 2017 S550 4-Matic, 2018 S63 AMG Sedan
If it were me I would clean the area as well as poccible, even if only from the top. Then drive for a short time, slowly so that things don't spread out as far, then come back and get it back up on the lift to see how things look.
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From: Phoenix
222 S-65
Did that last night Carlos. Fresh drop hanging from same spot tonight after commuting to and fro.
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2007 S600
Are you positive there is no coolant dripping down the side of your oil pan toward the front of thew engine? I have a leak/drip, my water pump and all the usual places are dry but still a steady drip off the passenger side of my oil pan once I pressurize the system above 12 pounds. I finally figured out it's a failed seal on the main front timing cover. Since it's failed up high there is no coolant anywhere on the front of the engine, just a drip along the seam where the cover meets the block. Needless to say, I wasn't very happy when I figured out the source.
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MBWorld Fanatic!
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From: Phoenix
222 S-65
Are you positive there is no coolant dripping down the side of your oil pan toward the front of thew engine? I have a leak/drip, my water pump and all the usual places are dry but still a steady drip off the passenger side of my oil pan once I pressurize the system above 12 pounds. I finally figured out it's a failed seal on the main front timing cover. Since it's failed up high there is no coolant anywhere on the front of the engine, just a drip along the seam where the cover meets the block. Needless to say, I wasn't very happy when I figured out the source.
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From: Phoenix
222 S-65
Mystery solved. Pull all plastic at cowl. Crane neck whilst shining flashlight and hold mirror..... The plastic guy that goes through the firewall and feeds heater has a hose on it that is leaking. It runs down to the driver's side and ends up pooling in side the chassis at L/F next to the strut. Not an expensive thing but sure looks like a treat to replace. I have a Saturday project. Woo-Hoo!
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From: Fleriduh
W212 E63S Wagon - GSL580 - E63 - E350 - C300
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2020 S560, 2014 SLK55 (Prev. 2016 S65, 2013 SLK350, 2008 CLS63, 2006 E350, 2006 CLS500, 2005 C230K)
So your charge coolant is pink and your main coolant is blue?That car did not leave the factory with two different coolants.
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From: Phoenix
222 S-65
The blue and red flavors are interchangeable; but only with a thorough flush. They are not to be mixed.
Up until now the worst leak has been the charge cooling reservoir and engine coolant reservoir caps. 11+ year old plastic.
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From: Phoenix
222 S-65
Replaced hoses and plastic bits. The guy that snaps into the firewall had developed a hairline crack on the cowl side of it. That assembly arrives with two hoses. Also replaced hose that clips into the plastic guy and goes to the pax side head. Pretty tight on the back of the engine and in the cowl. Cut my big meat hooks up pretty good. Three hours of effort start to finish. Zero drama. Nothing broke. Things are tight in there so getting to clamps was a treat. Worst was the hose on the head. I’d have the guys at the dealership do it, but not for the nine hours of labor they quoted.
Last edited by JohnLane; Feb 7, 2026 at 09:22 PM.
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From: Fleriduh
W212 E63S Wagon - GSL580 - E63 - E350 - C300
Exactly! The older I get the more I think that of some fool working at the dealership can do it so can i. Every single time I try one of these harder tasks somehow I'm always able to accomplish it in far less hours than what the dealership quotes.
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From: Phoenix
222 S-65
Mercedes offers pink as OE today. They stock blue in an aftermarket brand. Zerex if failing memory serves.
I like having different colors for the two cooling systems as I can see at a glance if a leak is charge or engine coolant.
If changing from one color to another; flush thoroughly with water to get all color out.
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From: Phoenix
222 S-65
Exactly. I’ve been a tech all my life. MB quotes astronomical labor figures to do things like engine mounts. “They have to pull the engine to replace them!” Um... BS! I was quoted something like 6.5 hours to replace engine mounts in my 211 E-55. First time I replaced them I had three hours in it. Subsequent replacements of mounts (they failed annually) got to under two hours. My 221 S-65 I was quoted over 20 hours “Have to pull the engine.” My first time doing them 3.5 hours. Subsequent replacements (again... failed annually) in under three hours. Seems they don’t need or want the work.
