slammer111

Has anyone ever seen this before?

My engine seems to be leaking coolant only when cold. I'm looking in the back underneath the vacuum pump and noticing what looks like dried coolant on the tranny case, directly underneath this pump.

When the car is running, nothing seems to leak. However, there's a puddle on the floor when I back my car out in the morning.

Physically below the pump is a coolant hose, which was covered dried/sticky engine oil from when my pump was leaking (which has been repaired since). No coolant - none I could see or feel at least. I wiped down the hose and squeezed the length of it, but couldn't find anything. There are also some dried coolant streaks on the exhaust pipe, up to the cat but not above. Not sure if that's just dried spillage from topping up the expansion tank though. I wiped it down and will look again in a few days.

The front end of the engine seems perfectly dry upon visual inspection. Absolutely no dried coolant.

Any ideas where I should start looking, before I throw more parts at the car? And MB is supposed to be over-engineered..

In this diagram, the hose that goes closest to the leak isn't shown. It's right where the number 124 is (ie connects to the "lower branch" of 130). Anyone have the diagram that would show that hose?

slammer111

Anybody?

Just crawled under the car. The bottom of the transmission housing is wet with coolant.

KSKarl

Try to get a mirror by the firewall to get a look at the back end of the engine.

SunnyRayToronto

Hmmm,.... maybe you need to spray some silicone lubricant on those rubber hoses! ;p

But seriously, try turning up the interior heat and fan to see if that encourages more coolant leakage. At the back of the engine, there should be a coolant hose that goes through the firewall to your HVAC - this brings the heat to your HVAC system. Let's hope its this hose and not a gasket.

slammer111

**update** Found the leak after several attempts. What an exercise this one was. At the back of the engine, there's a plastic coolant pipe. Didn't know it existed until now.

Finding this one was especially nasty because a) the leak only happened when the engine was cold/warm but NOT hot, b) it was almost impossible to see without using some kind of visual aid, and c) the leak went down both sides of the transmission casing, so initially I wasn't even sure which side of the engine it was coming from. In my case, I lowered my phone between the engine and firewall, and started taking photos. Looking back, I should've noticed the tiny wet spot on the part (circled in photo - it was much more wet, but I wiped it down before taking the photo). Without dismantling the engine, the pipe in question is only viewable from above, from the L fender of the car, between the rigid plastic tubes leading to the famous leaky vacuum pump. In the photo, the top of the photo is the engine (back side) and the bottom is the firewall.

The leak was where the O ring 73 is. Part 70 is made of the same crappy plastic as the breather pipe socket, pipe socket at the front of the engine, and water pipe feed line at the side of the engine, above the exhaust manifold.

Totally nice to see that all of these parts are exploding on so many fellow members. Hopefully this thread will save some of you guys a ton of pain. I won't mention how many times my arms got cut up reaching behind the engine. Some really sharp clips back there.

There may be more plastic bits around the M271 engine, but these are the ones I know of at this point:

003-997-06-89 Breather Pipe Socket (attaches to Part 130 in 1st post where the number 143 is; actual part not shown in diagram) - this nipple cooks and fails every few years from exhaust heat - also see this thread
271-200-12-56 Pipe Socket (Part 65 in 1st post) - also see this thread
271-200-13-52 Water Pipe - oil cooler to cylinder head (Part 70 in diagram in this post, this is what failed on me this time)
271-200-15-52 Water Pipe - feed line to cylinder head (Part 130 in 1st post)

12 years seems to be the magic number at which everything goes.

It's very disappointing that MB are using inferior materials that are known to fail. At this point I'm seriously considering aftermarket. What do you guys think?

SunnyRay, nope, I'm still not gonna lube the hoses. Looks like many of coolant ones are EPDM (it's stamped on the hoses), and honestly they seem as good as new in terms of flex.

SunnyRayToronto

Aftermarket parts are generally even more inferior than OEM Mercedes parts. I'd stick with the OEM Mercedes parts.

Knowing that these plastic parts fail, you might want to keep an eye on the calendar. M271 was last made for 2004 model year. By law car manufacturers have to make replacement parts 10 years after the last model was discontinued. Mercedes actually supply replacement parts for 15 years after last model was discontinued,.... last M271 was in 2004 model,... so stock up on these plastic parts in 2019 if you still have the car then.

VVF

In USA the last M271 was in a 2005 model.

Was it the o-ring or the pipe? So far it looks like only the rubber/o-rings deteriorate, which is 'kind of' expected at 10-15yrs.

slammer111

If I were to bet, I would say it was the plastic part that broke. The other O-rings I've looked at in the cooling system all still look brand new, even after all these years. Meanwhile, both the breather pipe socket and pipe socket have literally snapped in half on me.

Haven't removed the old pipe yet - need to order in the new parts first, as this car is my daily driver. Will give an update once everything falls into place.

SunnyRayToronto

VVF, thanks for the correction,.... M271 was also in 2005 model year car in Canada.

These Mercedes rubber/EPDM hoses are quite durable and last longer compared to my previous Honda. We really don't see many posters here complaining of busted-leaking hoses,... relatively,... well, except for that $12 vent hose.

slammer111

Just as I had suspected - the pipe cracked off where the O ring is located.

The job should've taken 1h, but ended up taking 3 as the bulk of the work was trying to get the broken piece out of the engine block. 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.

Aligning the piece was another real PITA. Patience is key. Be sure not to drop the bolt into the coolant hole! I almost had a heart attack when the bolt slipped out of my hand.

On a side note, can anybody find a part number for that hose clip in the photo? I'm actually missing one of these in the engine bay, but the dealer has no idea how to locate it.

Sunny, the $12 hose was superseded several times. Guessing they finally found a suitable material, as the complaints have largely disappeared.

samaritrey

Don't you love projects like that tell the wife/GF or whatever it will be an hour and then we will go to dinner. 3-10 hours later you come in all filthy, tired and pissed and then get to explain yourself. I guess being single again has its upsides

As for that hose clip your dealer can't find it lol well it will be in EPC but will probably take some time to find I would take a picture of it and send it to a few local dealers and say I need this here is my vin. One of them will find it for you.

VVF

Wow, some high-end plastic indeed. I wanted to just replace the o-ring on the pipe #130, but to avoid future troubles will replace the whole thing now...
Thanks for the heads up, slammer!

SunnyRayToronto

Is there a part number on that hose clip (plastic bracket)? Mercedes have parts number stamped onto the vast majority of their parts. If there's no part number, it's possible that little hose clip is packaged with the hose and sold together as a kit.

Using MBPartsWorld.com - which is same parts diagrams Mercedes-Benz dealer uses. Trying to look up that hose clip gives wrong part number (2208320314 actually for alternator bracket) - probably why your parts guy gave up.

I looked up similar part on SLK230 and it came out as 1705060241 for about $2.90 - I would try this one since SLK230 has M271 engine as well.
http://www.mbpartsworld.com/showAsse...rchString=hose


If the above diametre is wrong then maybe try the CLK320 version: 2095460243

slammer111

Sunny, thanks for the heads up. The parts you listed look exactly like the one I'd be looking for. There is no part number on the clip, which is why both the dealer and I had quite the time.

I'll let you know how things go with the dealer.

slammer111

Here's a YouTube example of the same leak. (not my video)

Contrary to what is said in the video, the firewall doesn't need to be removed to get to it. Simply disconnect the hose leading to the vacuum pump and "rotate" (the plastic pipe twists at the joints) out of the way, then reach in behind the firewall and engine. It's just barely enough room, but a ratchet and bit can be lowered into there to remove and replace the bolt.

SunnyRayToronto

Holly crap,... I just looked up that your broken fancy plastic L-pipe (271-200-13-52 Water Pipe - oil cooler to cylinder head) and it's $75US.... for a plastic pipe!!! WTF!
http://www.mbpartsworld.com/p/__/WAT...712001352.html

And that doesn't even include the rubber o-ring and bolt.

Slammer111,... In your photo in post #10, the newer part seems a bit shorter,... is it made of better material,... err, plastic!

slammer111

The part includes the O-ring but not the bolt. Every cooling piece I've purchased so far for this car includes the relevant O-rings. The bolts for any of these plastic pipes can be reused. Most aren't really load bearing - they're just there to keep the pipes in place. Yeah it's $75 CAD for the piece - this one is the most expensive out of the 4 I listed. Interestingly enough, many parts such as these are actually cheaper at the dealer as opposed to sites like RMEuropean.

In terms of material, it's still fibre-reinforced plastic (FRP), but the new parts have a different sheen - it's like they're using a different fibre matrix now. So yes it's the same type of material, but I wouldn't say it's the same material. Either that, or the old parts have degraded so badly that they don't look the same. The new parts look like a darker shade of brown compared to the old ones - think of a cup of coffee with 1 container of cream added vs. the same coffee with 2 containers added.

**update** The new part is 20% glass fibre instead of 30% glass fibre in the old parts as per the markings. Guess this makes the part more durable.

I'm not sure if the new piece is shorter - if it was, it wasn't by much. The clamp-like thing on the L side is just to keep a different unrelated coolant hose in place (the hose just pops in), so the length isn't too relevant. In other words, the piece in question is like a plastic pipe with a bracket attached.

VVF

Hmm, talk about reasonable prices

I'm thinking someone should start manufacturing those pipes from [aluminum?],
like the linkages for M272 from allgermanauto...

slammer111

So I finally got around to replacing the next coolant pipe. This is the physically big one (PN 271-200-15-52) above the exhaust manifold. Looks like MB has superseded this one - the original part was 271-200-11-52.

The part (the new one at least) includes the coolant sensor which comes installed.

Tools required:
Coolant extraction device (if you don't want to kill fish)
External Torx E10 bit
Various extensions - I used a 2", 3", 6", and 10" for this job; a flex extension would honestly be best in this case
Hose clamp tool (pliers *may* work if you're lucky)
Coolant for topping up (if required)
Pry tool (thin slot screwdriver or hook tool) for removing hoses and broken plastic bits from engine block

Instructions
1. Open and drain the coolant expansion tank. I only drained about 75% of it, but it was sufficient. As long as the level drops below the lowest point of the pipe (the connection with the O-ring), you're good.
2. Disconnect pipe socket (the flimsy one that seems to be exploding on everyone). Pry up the wire connector with a screwdriver, and unplug.
3. Disconnect the 2 connectors. One is the coolant temperature sensor; the other is some 3 wire connector and harness, not sure what it does. The latter broke on me (plastic is way too thin on this piece) when I was trying to unhook the tab. The part for that thin piece is 203-545-30-28, and the other half of the connector is 000-545-25-84.
4. Remove heat shield above exhaust manifold. 3 external Torx bolts. Note that one is slightly longer than the others - this one goes towards the front of the car. To get this thing out, I had to flex (almost to the point of bending it) the part to wiggle it out. There is 1 cable (goes around the power steering reservoir) that may get in your way, but on my car it was zip-tied. I simply fed more cable upwards to get the required slack. The cable can be fed back down through the zip ties after the job is complete.
5. Loosen 2 hose connections towards rear of car. Pliers may work depending if the tabs are at a good angle, but this I would imagine is luck of the draw. My hose clamp pliers took these off in seconds. Pry off the hoses, being sure not to damage them.
6. Remove bolts for pipe (2 total). A 2" or a 6" extension will work, but nothing in between because of another part in the way. A flex extension would probably work best here.
7. Remove pipe. The O-ring connection is tight - wobble the pipe back and forth and eventually it'll pop out.

Reverse everything when done and you're good to go.

Looks like the 15-52 piece is made of a different kind of fibre-reinforced plastic. The plastic is black instead of dark brown, but the fibers have a much more shiny appearance. The old pipe is the top one in the photo. I imagine the updated PN has a lower glass fibre content just like the other pieces I replaced.

slammer111

Sunny, the correct fastener turned out to to be 209-546-02-43 ($3).

The 170 part is easier to unlatch as there's a tab built in for unlatching, while the 209 has a "hook" style catch. Also, even though both clips are attached through a hole in the substrate, only the 209 has a middle plastic push pin for expanding the tabs once the clip is fastener is in place.

Thanks for the info. If you're ever in my area, beer's on me.

SunnyRayToronto

In the vast majority of threads, an Original Poster would post a problem and somebody would post possible solutions or opinion, Original Poster would go off and try some of those possible solutions,... but we usually never hear back from the Original Poster so we usually do NOT even know if our suggestion fixed the Original Poster's problem or not. And thus, those threads become less useful.

Here, we have a thread where the Original Poster, Slammer111, did the usual seeking assistance to solve a problem,... but also posted detailed updates and feedback while investigating the problem along with a thorough step-by-step Do-It-Yourself solution with all part numbers needed. This is what makes threads like this valuable,... problem with possible solution, feedback, updates and DIY steps with part numbers!

Thanks Slammer111, you're a true credit to this forum and this thread will definitely help others.

Preet

+1 well said

PelicanParts.com

Yes, agree, very useful thread. If you come about anything else that needs fixing we have some good DIY tech articles here that may be of some assistance. Good job with this one!

-Luccia

jaeee

Yessssss! Thanks Slammer!

http://postimg.org/image/jj3ke81on

Miguel Angelbx

Can someone please tll me the part number? Im having the same leak. Thank you