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Looks like someone worked on your car (possibly replacing the pipe in your last photo) and forgot to clip the hose properly. The clip isn't broken. Just pry it open with a screwdriver, rotate it 90 degrees, and pop the hose inside.
Your leak may be something else, such as an adjacent hose. When the pipe at the back of the engine fails, it normally soaks the entire pipe on the outside and makes a huge mess. In your last photo the pipe looks perfectly dry. Can you trace the dried coolant upwards?
Personally I found it was easier to lower a smartphone into the back area and snap some photos to confirm the source of the wetness.
Why is your coolant sky blue?
Last edited by slammer111; Mar 22, 2024 at 08:36 PM.
Thanks. I was out of town for a week and I haven’t driven the car since last Wednesday. The leaked coolant may have evaporated. I will use my phone to take more pictures tomorrow.
I have limited information about the car’s maintenance prior to my ownership. I bought it almost 7 years ago when it had 112,000 miles on it. I can’t rule out the possibility that the pipe was replaced previously. I have a record showing that a previous owner replaced the valve cover gasket. That is the only documentation I have of any work that was done to that area of the engine. I don’t think that would have required removing the clip from the hose.
Your leak may be something else, such as an adjacent hose. When the pipe at the back of the engine fails, it normally soaks the entire pipe on the outside and makes a huge mess. In your last photo the pipe looks perfectly dry. Can you trace the dried coolant upwards?
Why is your coolant sky blue?
I took the car on a short drive the other night. This morning, I felt around the pipe, and it was damp. While I'm not absolutely certain the pipe is the source of the leak, it appears likely that it is.
I think it is sufficient evidence that the coolant pipe is leaking for me to proceed. (Sorry for the poor quality.)
My coolant is blue because I'm using Peak European coolant. It was the only European car coolant I could find conveniently when I replaced the water pump about 4 years ago. The Peak European coolant uses an HOAT formula which, according to this article, is the correct formula for Mercedes from the early 2000's until 2015. From what I can tell, the Peak coolant has worked fine, but if you have additional information on the topic, please let me know. The topic of Mercedes coolant is one with which I'm not 100% comfortable.
Last edited by KevinH2000; Mar 27, 2024 at 12:05 PM.
The bright blue smudge in the video is the telltale sign of a leak. You're looking at a new pipe, which should include the o-ring. Nice and easy. Just make sure you have something for prying out the broken piece and old o-ring.
I'm not sure all HOAT formulas are identical, the same way not all coolants are identical. In fact, I don't see anything from Peak in the list of MB approved coolant 325.0. Who knows if it's slowly corroding the coolant system. Personally I'd do a drain and fill with the correct stuff. A new jug of coolant is much cheaper than a new radiator.
I removed the pipe last night. Like the coolant pipe encountered by everyone who posted on this thread, mine is broken at the indentation for the O-ring. I had already purchased the OEM replacement pipe. I guess I should be glad that I made the right diagnosis - lucky me.
I wasn't able to remove the broken piece from the engine block last night. I was running out of time and decided to stop before I made a mistake. I re-read your guidance on removing the broken piece this morning: The trick is to jam a screwdriver into the O ring and force part of it out, where it can be grabbed to pull the entire ring. Once the ring is out, the plastic piece falls out.
I will use your technique later today. As anyone who has done this work knows, the challenge is that the work area is difficult to access.
I will check into the coolant issue more thoroughly.
Taking a break and Slammer’s O-ring removal technique proved to be a winning combination. I was able to remove the O-ring and the broken plastic piece in about 5 minutes when I started fresh.
If I had to do this work again, I could complete it in half the time, However, I may decide to sell the car instead. This is an unpleasant task. Thanks again to Slammer and the other contributors for sharing their experiences.
Evidence of my success removing the coolant pipe and the parts that were stuck in the engine.
Last edited by KevinH2000; Mar 28, 2024 at 06:37 PM.
Hi, finally became a member after learning a lot from this particular thread and thank you slammer and everyone else that shared their experience around this issue!
I purchased my 04 C230 SS on 3/28/2024 and it lasted 10 days... then the coolant leak happened. As everyone else, the culprit was the plastic oil cooler water pipe (2712001352) and took all the plastic bit. I found hook tool was very useful. Also, flexible ratchet made it easy that was for sure! For the hook tool and flexible ratchet (both came with 3 sizes), I paid $25 at Harbor Freight.
Now I am to order all the necessary parts (incl. control arms etc.).
However, I am stupid enough to think I should make more space for easier pipe installation, so that I tried to take off the plastic connector thingies. One on the driver's side I could take off with no issue, but the one located above the oil cooler pipe, that connected to the vacuum pump I couldn't take it off, so that I used a plier and it BROKE Now I have to order replacement for it, but I can't get the parts number or name of it.
Can anyone help me out and advise me the part number or the name of the part? I am not sure if I have to replace entire hose with connectors or I can replace just the connector
I found the part number by myself.
Wow my stupid decision to break the connector and make space cost me... The thing is Power Brake Booster Line (2034305729) and I found the connectors & hose needs to be replaced entirely. No after market available, and genuine mercedes part cost around $200. Yes its always me doing stupid stuff like this, if its just the coolant pipe, then it didnt cost me more than $50 incl. tools I purchased at HF.
Sorry to see that happened. I was able to remove my coolant hose without removing that part. My hands are just small enough to fit behind the engine block. I bought the same Harbor Freight ratchets that you bought.
In my first attempt at installing the replacement pipe, I pinched the O-ring between the inlet and the pipe. That probably wouldn't have happened if I had removed the assembly that you removed and made more room to work. I was working by feel and I must not have aligned the pipe correctly which caused one side of the O-ring to peel off and get caught. I only discovered my mistake because I took a video with my cell phone to check my work. The O-ring didn't appear damaged, but i bought another one at the dealer just in case. Even though the O-ring cost a ridiculous amount ($10.95) I considered it cheap insurance.
Last edited by KevinH2000; Apr 12, 2024 at 09:29 PM.
I was able to remove my coolant hose without removing that part. My hands are just small enough to fit behind the engine block.
Same, my hands are small enough and I too could remove the pipe without taking the booster line out... I should have stopped there so that I could have saved $200 and could use that money for some other preventative stuffs.
But its too late lol I'll try to remove that entire brake booster line tomorrow and will take pictures and post them here, in case some others need reference. Hope it comes off easy, the only thing I have to remove is the part where connected to the firewall area.
Besides, has anyone needed to replace the hose that is attached to the coolant pipe? The side where goes to cylinder head which degrades is the main topic of this thread, but the other side is connected to the hose, and I am talking about that hose. Anyone needed to replace that hose? Or just left that hose untouched?
My hose itself looks ok, but the very tip of the hose, the excess where outer side of the hose where the clamp holds, is kind of torn, like 1/8" (the shaded in my drawing). I was thinking to replace the entire hose but it seemed like I could cut the torn part because affected was just under 1/8", so I cut it. After I cut it, I tried to re-install the broken coolant pipe just to see if the slightly shorter hose would still fit ok or not, and it looked ok.
But I was curious if any one has replaced it or not... it looked like it involves entire intake removal.
Honestly I'd try a wrecker or online (eBay etc.) for the vacuum pipe assembly. They're not known to fail at all, so any used one will do the job.
Any hose can be replaced. I'm not aware of anyone with a damaged hose back there. I imagine any damage would be from rough disassembly (using the wrong tools etc.). If you're able to cut out the damaged section without introducing new cracks, then you're good to go. For any critical hoses (coolant, fuel etc.) personally I would rather replace the part than risk getting stranded or doing permanent engine damage if something fails. I believe that hose attaches to the oil cooler, which is accessible with the intake box removed. See link. Which brings us to the next topic - make sure your crankcase check valve is intact (same thread).
Last edited by slammer111; Apr 13, 2024 at 02:27 AM.
Honestly I'd try a wrecker or online (eBay etc.) for the vacuum pipe assembly. They're not known to fail at all, so any used one will do the job.
Any hose can be replaced. I'm not aware of anyone with a damaged hose back there. I imagine any damage would be from rough disassembly (using the wrong tools etc.). If you're able to cut out the damaged section without introducing new cracks, then you're good to go. For any critical hoses (coolant, fuel etc.) personally I would rather replace the part than risk getting stranded or doing permanent engine damage if something fails. I believe that hose attaches to the oil cooler, which is accessible with the intake box removed. See link. Which brings us to the next topic - make sure your crankcase check valve is intact (same thread).
I just took off the vacuum line, that wasn't difficult job. Simply pulling it get the job done, was easier than the other ends.
This gives another headache... the parts I found on AutohausAZ has a little tip (in the red square: that black nipple) which I believe another hose would be attached to... whereas mine doesn't have it.
All the vacuum line I could find online has the same "extra nipple". However, I assume I can just put some sort of cap and seal the tip and that should do the job, what do you think?
Also, I checked with ebay and the local junk yard and got no luck. They got the same year, but was V6 model in the yard, no 4cyl M271.
Also I realized that the vacuum pump has some oil leak. Its not severe, but when I reach to the underside of the pump. my glove does get oil. I guess I have to replace the pump along side the coolant pipe and vacuum line
I imagine the extra nipple doesn't do anything. All the pump does is draw vacuum out of the brake booster (where the nipple is). As long as the new one can fit inside, I can't imagine it being an issue. It might be some relief valve. Worst case, just plug the nipple with some RTV.
The original brake booster vacuum pump has a 100% failure rate. The o-ring between the 2 halves of the pump casing goes bad and causes the leaks. While it may techinically be possible to open up the pump halves and replace the o-ring with a RTV seal, honestly it's easier to just get the updated pump which includes the new style gasket.
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... then the coolant leak happened. As everyone else, the culprit was the plastic oil cooler water pipe (2712001352) and took all the plastic bit. I found hook tool was very useful. Also, flexible ratchet made it easy that was for sure! For the hook tool and flexible ratchet (both came with 3 sizes), I paid $25 at Harbor Freight.
Now I have to order replacement for it, but I can't get the parts number or name of it.
