I have a coolant leak that appears to be coming from one of the hard plastic water pipes.







To provide some perspective, the photo above shows the end of the pipe that is closest to the front of the car. This photo shows the entire pipe:





It is the rigid black plastic pipe located above the exhaust manifold from the rear of the engine to the front.

Based on post #28 in this thread it is labeled as #130 ... A 271 200 15 52 ... Heater feed, at cylinder head.

Before I start spending money and throwing parts at the problem does anyone think I'm on the wrong track if I replace this part?

I am also wondering whether replacing just the O ring (part #140 in the diagram) might fix the problem.

Thanks in advance for any assistance or guidance.

 

Here's a picture from another thread of the pipe removed from the car.

My current thinking is to replace the "Seal Ring" (Part # A0279979048) and see whether that solves the problem. If that does not fix it, I will order the entire pipe. Unfortunately, when I put the part number for the pipe into some of the on-line sellers' part search the web sites show what appears to be a different part.

 

You can replace the O ring, but there's probably a reason the PN was updated.

For reference, can you post a better photo of the markings about halfway down the length of the existing pipe (post #1, 2nd photo), or type out the characters? The markings show the exact material the pipe is made of.

When I had a coolant leak at the back of the engine, I ended up replacing 3 pipes in total, including the one over the exhaust manifold. I found that the pipe at the back of the engine was made of a different material (same plastic but lower % of glass fibres) than the old one. Meanwhile, the material for the large pipe at the front of the engine was unchanged. Unfortunately I didn't check the material of the one above the exhaust manifold.

At this point, either the o-ring is bad, or the pipe has cracked off where the o-ring is. Some people have had this pipe crack. On my car the pipe and o-ring were fine, but the pipes at the front and rear of the engine cracked at the o-rings. I replaced the one over the exhaust manifold preemptively. You may want to change out all 3 as well to solve the problem permanently. For me, I was dealing with a new leak every 2 weeks (the pipes were failing one after another), so I decided to replace everything and get it over with.

 

I saw your thread on the coolant hoses. I think you make a good point about replacing the pipes proactively. I have some other items on my agenda right now, but I may start planning to replace the hoses before fall.

I couldn't take a good photo of the part number, but it is A 271 200 1152. Do you know the part number for the revised part?

I called the local dealer. They don't have the O-ring in stock. I ordered it and it will arrive Thursday due to the holiday.

 

The revised PN is 271-200-15-52. Just like the one in your post #2. The dealer will know if there's a newer PN.

The material marking should look something like >PA66 xxx<. I can see the markings in your post #1, 2nd photo (middle of the pipe), right underneath the PN, but can't read the letters clearly. Wondering if you can post a clearer photo. Thanks in advance.

PNs for all the other pipes are in the link I posted earlier.

The reason it's easier to replace all 3 pipes + nipple in question is that the jobs involve a partial coolant drain (the level needs to be at the bottom of the expansion tank) and refill. You'll be doing this 3-4 times if you replace each pipe separately. While you're at it, check your expansion tank to see if it also needs replacing. The top section (black part) starts to crumble like a cookie.

 

Sorry for the delay

P A 6.6 GF 30

Thanks

 

Thanks for the info.

I just checked the pipe above the exhaust manifold on the car (I have 15-52 installed) and it says PA6.6 GF 30 as well. In other words, they didn't update the pipe material. They may have simply updated the o-ring for the new PN. In this case you can get away with replacing just the o-ring unless the pipe has physically cracked there. Of course this is assuming MB didn't change any physical dimensions for the pipe.

FYI MB updated the pipe at the back of the engine to a different material (GF 20 new vs GF 30 old). So you probably want to update the physical pipe on that one. The rear one has a very high failure rate.

 

Thanks Slammer. I'm in the middle of a home maintenance project. I should have time this afternoon or tomorrow to drain some coolant, remove the pipe and check for the source of the failure.

Your guidance on replacing the other pipes is correct. I've owned the car for almost 5 years and in that space of time, I've replaced the bottom radiator hose, the water pump, the thermostat and the coolant overflow tank. The limited records I have from the previous owner show that he replaced the top radiator hose about 6 months before I purchased the car. Each of the replacements was done on an as-needed basis. Doing the jobs together would have been far more efficient.

The challenge I faced when I worked on the other projects is the same I face now. That is, I prefer to perform my own repairs but I'm a slow worker and I have other demands on my time. I'm planning to review your thread on replacing the pipes and estimate the amount of time it will take me to complete the work. If I recall correctly, you needed about 3 hours to replace all of the pipes. My guess right now is that I will need to set aside at least one weekend day to take care of it. If I can't find the time, I may need to replace the O-ring until I find more time.

No matter which path I follow, your instructions in post #19 of your thread will prove helpful. Thanks for taking the time to post them.

 

I'd say 1h for each pipe (possibly 1.5h for the exhaust manifold one) if it's your first time. The other ones are literally just 1-2 screws. I can do the ones at the front and back of the engine in 10-15 minutes at this point.

Most of the time is actually spent trying to get the broken piece and o-ring out if the pipe has broken off. Pro tip - use something sharp and pointy like a pick tool and "stab" the o-ring to pull it out. Be sure not to damage the mating surface of the engine.

When doing any job that can potentially leave me stranded if the job goes sideways, I always make it a point to not have anything booked later in the day. We all know how a 1h job can turn into 8h if something gets stuck or broken along the way.

 

Sorry been inactive on here for awhile but slammer is correct. I recently replaced that part as preventative maintenance when I removed it the part with the o-ring attached broke off. Chances are when you go to remove it that it is going brittle and breaks on you. I did not drain the coolant for this job I just kinda let it spill out while I replaced it which it wasn't a lot between taking it off and putting on maybe 5 seconds.
( I just replaced the coolant lost )
The part number I have is A271-200-15-52 it also came with an O-ring on it when I purchased from the dealer. I would buy an extra o-ring when I replaced mine there was a sharp edge some where in that space I was carless and some how the o-ring was damaged when I reinstalled. Had me scratching my head for a while on what I did once I removed the part again I saw the o-ring had been torn. My dealer did not have any extra o-rings in stock and it was the weekend so I had to pause the job until I received my new o-ring. I have always purchased extra bolts and o-rings now when performing a job because chances are one of the bolts might be stripped or i'm going to lose one lol.

O-Ring Part # 027-997-90-48 ( Water line to cylinder head )

FCP has the part for $62.99 and O-ring for $1.79

Shouldn't take more than an hour...

Now the rear one was a pain with the tight space and it was stuck and pieces where broken had to use a pick.

Good Luck

 

One other tip - stick to the dealer for stuff like o-rings. Only the dealer knows the correct material. I've had aftermarket o-rings go bad over time in the past. Meanwhile every dealer o-ring has held up over the years.

 

The end of the pipe adhered to the inlet.

I found some time to check whether the problem was caused by a failed O-Ring or a cracked pipe. This photo shows the answer to that question.

I don't know whether the pipe had separated into two parts, or it was cracked and removing the pipe finished the job. I guess the actual chain of events doesn't matter. I need to cancel my order for the O-Ring and order the entire pipe assembly.

My dealer has been willing to price match and I hope they retain that policy. They usually obtain the parts in a day or two and since I can't drive the car in its current state, the quicker I can complete the repair, the better.

Slammer - Your instructions for removing the pipe saved me a lot of time. Thanks for posting them.

 

I finished the job this morning. Thanks again to Slammer for his advice.

Side-by-Side Comparison of original and replacement pipe showing failed section at the end of the original part.

I will watch the car closely for the next few days to make sure there aren't any leaks.

Fortunately, my local dealer was willing to match price with on-line sellers and the part was "only" $62 with no shipping charges.

 

Glad to see the problem has been fixed. Hopefully you had a chance to inspect the other 2 pipes and the nipple. The pipes won't be far behind.

 

The other parts are not leaking now, but everything in the car that hasn't been replaced already will be 18-years old in a couple of months. I expect that it is only a matter of time. I'm gambling that everything will hold together until I have more time and can replace the other pipes on a preventive maintenance basis.

As I mentioned earlier, I'm a slow worker in the context of auto repair. This is especially true for a new task. I triple check everything and there are some items such as removing parts in a tight or restricted space that require multiple attempts before I determine the correct technique. Yesterday was a prime example. It took me about three hours to replace the pipe. The stumbling blocks were:

1. The hose clamp on one of the pipe sections (the lower part of the y-shaped section at the back of the engine) was in a difficult spot to access with my pliers. I was eventually able to position it correctly for access, but I worked carefully and slowly to avoid breaking anything or damaging the hose. I usually find that applying brute force leads to bad outcomes. Fortunately, I had the correct pliers for removing OEM Mercedes hose clamps and once I had it in position that part of the job went smoothly.

Tool for removing Mercedes hose clamps.

2. Reinstalling the two fasteners that hold the heat shield to the back of the engine block took a comically long amount of time. The fasteners are in awkward/tight spots and my dexterity was challenged. It didn't help that I dropped both bolts and needed to retrieve them using my magnet tool.

3. The fastener that holds the pipe to the front of the engine block is in a tight spot too. I was able to secure it using the tools I had. The technique I used was to first insert and tighten it with my fingers. Once it was as tight as I could get it with my fingers, there was just enough room to squeeze my ratchet in and tighten it all the way down. The next time I'm at Harbor Freight I plan to buy a swivel for my socket wrench set. I think that would have made that particular task easier. (Your thread suggested that a swivel might help, and I should have considered it mandatory.)

I've read your thread on replacing the other pipes a couple of times and I am attempting to reach a better understanding of the job. I have access to a lift at an auto hobby shop and I'm wondering whether that might make the job of accessing the pipe at the driver's side between the firewall and the engine block easier. Your thread seems to suggest that accessing one fastener may be easier from below than from above. When it stops raining, I plan to look more closely and start visualizing the process I will need to follow.

 

The pipe at the back of the engine can't be accessed from below, as the transmission is in the way. It's actually not too tough to reach down from the top as long as you understand how to swivel the hard plastic pipes out of the way.

The pipe at the front is very accessible from above. Just unhook the cloth intake hose and move it out of the way. Sounds like you've already replaced the thermostat so you've removed the part before. One piece of advice here is to keep a spare o-ring (the one that fits in the "middle" of the plastic pipe, not the one at the end between the thermostat and the pipe) handy if you bought an aftermarket thermostat. The included o-ring had the correct dimensions but was made of the wrong material. It stretched over the years and created a slow coolant leak, necessitating another trip to the dealer.

The pliers in your photo are for Clic-R hose clamps. Can you show me where you found this on the cooling system? The only places I have found these on the car are on air hoses (crankcase breather including the $12 hose, and fuel vapour) and the fuel filter.

 

Is it possible for you to tell me the part number of the bolts that attach the pipe. I dropped both of them and can't even see where they are so i need to get a couple just to be able to finish this job. DAMMT. THANK YOU IN ADVANCE.