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Last winter I got a low coolant warning, took it to the dealer, said that I thought I had a coolant leak, they said they didn't find a leak, topped it up with coolant, sent me on my way. A few days ago I got the light again, checked and saw the coolant looked low and that there was coolant residue all over the expansion tank, seemingly coming from the cap. Bought OEM coolant, mixed with half distilled water, added a couple of cups (couldn't find the fill marker) and the message went away. Yesterday I saw a visible leak below the car, it was back down to its low level with the light on again, and there was a tiny bit of residue on the top of the expansion tank that I had cleaned off. Not enough residue to be the whole leak. The level was the same as before I re-filled it, a few inches below the top of the bottom, translucent portion of the tank.
Still waiting another week on my appointment with the dealer. Could it be a head gasket? Anyone have any similar issues? I've seen a few posts on the forums about leaks from the caps but this can not all be leaking from the cap. Anyone have any idea where the fill marker is for the c63s? My tank doesn't seem to have the marker that my c300 manual seems to indicate it should. Before cleaning and refilling After cleaning and refilling (the level was a bit higher but already had started leaking again)
Most likely just a faulty cap. Does the engine or trans overheat? I replaced my cap at relatively low mileage for a faulty o-ring seal on the main expansion tank.
Most likely just a faulty cap. Does the engine or trans overheat? I replaced my cap at relatively low mileage for a faulty o-ring seal on the main expansion tank.
No, temps are all normal. Oil no higher than ~223 after the hardest of hard pushing, about 215 more generally. Thanks for sharing about your cap.
Regarding a possible overfill, how would I even know what to fill it to? Does your tank have the little cross that is indicated by our c300 manual in the bottom of the tank? Mine doesn't seem to even have that marker. And the manual seems to just be a c300 manual with an AMG supplement that makes no mention of coolant.
Last edited by turboszn; Jan 16, 2024 at 09:42 PM.
I usually fill mine a little bit halfways from the seam across the exterior of the expansion tank. Mine does not have that cross. It’s a bit misleading in the owners manual.
Interesting. Sounds confusing on purpose so that it's a dealer that overfills it and not the owner or a private shop.
Last August I noticed residue around the expansion cap (2019 C63s coupe). I called MB MB Dealership and SA bring it over. So that morning while the engine was cold I opened the hood and realized the cap was not properly sealed. I turned it until I heard the click.
I still went to the MB service where the tech. cleaned the outside tank, did a pressure check and said it may have had too much antifreeze in it or the cap was not properly sealed. I never messed with it but had the yearly service at MB in April. So who knows if it was carelessness.
Since I was already at the Dealership I was going to purchase a new cap about $55.00 just to be
sure but the tech said everything checked ok and did not feel I needed a new cap but did say keep an eye on it and if so then purchase a new cap.
Your post is a good reminder for me to check it now
as I have not looked for some time.
Last August I noticed residue around the expansion cap (2019 C63s coupe). I called MB MB Dealership and SA bring it over. So that morning while the engine was cold I opened the hood and realized the cap was not properly sealed. I turned it until I heard the click.
I still went to the MB service where the tech. cleaned the outside tank, did a pressure check and said it may have had too much antifreeze in it or the cap was not properly sealed. I never messed with it but had the yearly service at MB in April. So who knows if it was carelessness.
Since I was already at the Dealership I was going to purchase a new cap about $55.00 just to be
sure but the tech said everything checked ok and did not feel I needed a new cap but did say keep an eye on it and if so then purchase a new cap.
Your post is a good reminder for me to check it now
as I have not looked for some time.
Interesting. Thanks for sharing. Did the dealer happen to tell you how to be sure it doesn't have too much antifreeze? Lol. I've got no markers and no manual.
Interesting. Thanks for sharing. Did the dealer happen to tell you how to be sure it doesn't have too much antifreeze? Lol. I've got no markers and no manual.
No. The SA had the tech waiting when I arrived so "gratifull" to both. No mention if any coolant was removed or added.
When I opened the cap that morning it as I remember was half full or so.
Today (see photos) the outside tank see relatively clean but a small amount of residue on one side. Inside the cap seems to have some residue around the inside threads.
The inside tank appeared to just fall just below where the translucent section meets the dark tank. So not sure if that is where it should be when the engine is cold.
Also I am going to view my MB Service invoiceithst was done in April, 4 months early. I be looking to see if any coolant was added and possibly too much or just neglect to tighten the cap. Or is it time for a new cap.
So other feel free to comment on
the condition of these photos. Do I need a new cap or is this somewhat normal
?
No. The SA had the tech waiting when I arrived so "gratifull" to both. No mention if any coolant was removed or added.
When I opened the cap that morning it as I remember was half full or so.
Today (see photos) the outside tank see relatively clean but a small amount of residue on one side. Inside the cap seems to have some residue around the inside threads.
The inside tank appeared to just fall just below where the translucent section meets the dark tank. So not sure if that is where it should be when the engine is cold.
Also I am going to view my MB Service invoiceithst was done in April, 4 months early. I be looking to see if any coolant was added and possibly too much or just neglect to tighten the cap. Or is it time for a new cap.
So other feel free to comment on
Definitely similar to my experience. They don't seem to tell me if they added coolant or not, and the residue builds up pretty quick. Mine is dropping to a level that throws the 'low coolant' warning within days though, so I'm gonna take it in and see what I can find out.
Looks like the O-ring seal might be leaking a bit. I would recommend replacing it. Mine failed at 14k on my 21.
Definitely will do. Could that o-ring leak really cause it to lose like 2 cups of coolant in a few days? I didn't see 2 cups worth of residue on the top but maybe it didn't dry out or something.
Definitely will do. Could that o-ring leak really cause it to lose like 2 cups of coolant in a few days? I didn't see 2 cups worth of residue on the top but maybe it didn't dry out or something.
Our cars have a big skid plate where the coolant can be pooling up. If you’re hesitant have the dealer do a pressure test on the high and low temp circuits to verify no external leaks. You might have another leak somewhere but hard to verify without a pressure test. When I had a leak mine was the cap. Make sure you tell them you want a coolant pressure test. Show them the photos for proof. As far as it being a head gasket leak it’s not likely at all since your car is not overheating. It takes some serious aluminum warpage/deformation of the head sealing services to cause an external leak from the head gaskets. If it also helps my thermostat was replaced under warranty at 18k for a mechanical failure not a leak. They have extended the warranty for the T-stat up to 150k miles or 10-15 years via letter in the mail for owners that get an engine light for code p0128.
Our cars have a big skid plate where the coolant can be pooling up. If you’re hesitant have the dealer do a pressure test on the high and low temp circuits to verify no external leaks. You might have another leak somewhere but hard to verify without a pressure test. When I had a leak mine was the cap. Make sure you tell them you want a coolant pressure test. Show them the photos for proof. As far as it being a head gasket leak it’s not likely at all since your car is not overheating. It takes some serious aluminum warpage/deformation of the head sealing services to cause an external leak from the head gaskets. If it also helps my thermostat was replaced under warranty at 18k for a mechanical failure not a leak. They have extended the warranty for the T-stat up to 150k miles or 10-15 years via letter in the mail for owners that get an engine light for code p0128.
Thanks for the insight. I have my service appointment in a few days. Will update once I know something.
So the dealership said there's a leak in the radiator, caused by possibly a rock? They said they pressure tested and that the additional pressure from the leak (makes no sense) is what was causing the cap to spew out coolant. Somehow not covered under CPO.
That’s unfortunate. There is a protective mesh protecting the auxiliary cooler so you must have nicked it pretty good. Since it was caused by “road debris” that’s their way off wiping their hands clean of any warranty work.
2010 BMW E63 M6 Coupe 2023 AMG C63s Coupe 2005 YZF-R1
Originally Posted by Shlick96
That’s unfortunate. There is a protective mesh protecting the auxiliary cooler so you must have nicked it pretty good. Since it was caused by “road debris” that’s their way off wiping their hands clean of any warranty work.
Sorry to hear this happened. You probably could go through your insurance. If it was a rock/debris that caused the puncture to your radiator, it should be covered by comprehensive. If this was my car, I’d go through insurance since my comp deductible is $0.
⏱️ 700HP Facelift converted C63 S Coupe with Drexler 3.06 plated LSD
Originally Posted by turboszn
So the dealership said there's a leak in the radiator, caused by possibly a rock? They said they pressure tested and that the additional pressure from the leak (makes no sense) is what was causing the cap to spew out coolant. Somehow not covered under CPO.
That's f*cken steep. Can't believe this is still happening after all these years.
If that were my (facelift) car I'd upgrade to Modalworks PWR coolers. You can paint over them or use paint remover if you don't want logos etc. but there is just no way I'd pay that much for these stock crumbly coolers again. I actually had this happen to me twice in the past before Mercedes secretly added their little mesh update. After the second time I said nah and upgraded them.
The funny thing is I have run no mesh protection on my Modalworks coolers for 2 years now and driven the car thousands of miles have never had any punctures or other "rock hit your cooler" problems since so it's the stock coolers that just can't handle anything.
Really sh*ts me that Mercedes still blames the client instead of at least offering a goodwill replacement.
This happened to me 2 times on my PFL..... once without the mesh when I first bought the car then it happened AGAIN with the mesh that I had to pay $200 for. I will get upgraded ones when these ones get punctured.
That's f*cken steep. Can't believe this is still happening after all these years.
If that were my (facelift) car I'd upgrade to Modalworks PWR coolers. You can paint over them or use paint remover if you don't want logos etc. but there is just no way I'd pay that much for these stock crumbly coolers again. I actually had this happen to me twice in the past before Mercedes secretly added their little mesh update. After the second time I said nah and upgraded them.
The funny thing is I have run no mesh protection on my Modalworks coolers for 2 years now and driven the car thousands of miles have never had any punctures or other "rock hit your cooler" problems since so it's the stock coolers that just can't handle anything.
Really sh*ts me that Mercedes still blames the client instead of at least offering a goodwill replacement.
It was just one auxiliary cooler so I ended up doing OEM. But this is an interesting idea for the future. The private shop confirmed the diagnosis with an additional pressure test and replaced it. It was leaking from a seam and the indy shop said it seemed like a part failure rather than rock damage. No indication of rock damage. Very odd. Wondering if it's just from running it hard in the Texas heat or just bad design?
Going to also have an oil sample tested to check the engine health, but none of the techs I've spoken to believe it's any indication of head gasket or engine issues.
This happened to me 2 times on my PFL..... once without the mesh when I first bought the car then it happened AGAIN with the mesh that I had to pay $200 for. I will get upgraded ones when these ones get punctured.
Sorry to hear about it man
Thanks George.
Seems like it was a defective/failing part rather than a puncture. The indy shop I go to said it's common on the main radiator but they hadn't seen it on the auxiliary radiators for these cars before.
Interestingly enough, the auxiliary radiator on the passenger side, the one that was damaged, is attached to the main coolant circuit rather than the secondary one. If it had been the radiator on the driver's side, it would have leaked the second circuit, or so they told me.
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