bigspender101

My coolant light went off about 2 weeks ago so I checked it and it was about an 1 1/2 inches down from the top. There were no visual signs of a leak since I didn't see any on the ground nor did I see anything near the reservoir, Hoses ect.. So I filled it up and went on my way. Well, 2 weeks have gone by and same thing. So I dug in a little deeper and I think I found where the leak is. Its dry underneath so it must be leaking out and then evaporating...Im not sure what this hose is called and how easy it is to replace???? Any Ideas? Pics below! This is a 2003 c230k by the way...

jcnash

Tis the season for coolant leaks it seems....

So many threads all of a sudden (including mine) related to coolant issues. Whats going on?

Carsy

Looks as though the aluminium casting is cracked ! Can't tell you the name.

bigspender101

It looks cracked in the picture but I believe it is the flange piece that connects the hose to the block that is cracked....I need to investigate it a little more to find out. That's why I am asking if anyone knows what this part is?

bigspender101

Wow, 150+ views and no one has any input!

Carsy

Unusual ...... Can't help you mate, I have a diesel.

jcnash

Post a few zoomed out pics..with an arrow pointing to the general area of the engine bay.

That pipe looks like one of many pipes in the engine bay...how are we supposed to know which end/which pipe?

Carsy

Bigspender,

In this case I would draw a freehand map of the problem pipe going in the block & take this with your engine number to the dealer. I would ask them to look up the part number & actually show you on their screen the diagram to make sure they have the correct one. You then should be able to receive a quote. Also ask them if any other parts are required eg seals, gaskets, O rings,etc.

Good luck & let us know how you go .

bigspender101

Here are a few more pics zoomed out...I think I will just go to the stealer and see if they have a part number...

Glyn M Ruck

Let me know if you need a part number.

bigspender101

Actually if I could get the part number that would be great.

Glyn M Ruck

5 A 271 200 02 01 WATER PUMP
PARTS KIT 001
17 A 271 203 02 80 .GASKET
WATER PUMP TO TIMING CASE 001
20 A 601 992 04 25 FITTED SLEEVE
WATER PUMP TO TIMING CASE 001
23 N 000000 0001119 SCREW
WATER PUMP TO TIMING CASE
M6X33 005
26 N 910143 3008011 SCREW
WATER PUMP TO TIMING CASE
M8X90 001
32 A 271 202 01 10 PULLEY
WATER PUMP DRIVE 001
35 N 000000 0004310 SCREW
PULLEY TO WATER PUMP
M6X10 004
56 A 271 203 03 75 THERMOSTAT
90 DEGREES
Replaced_By: A 271 200 00 15 001
56 A 271 200 00 15 THERMOSTAT
90 DEGREES 001
65 A 271 200 12 56 FITTING
COOLING WATER OUTLET 001
68 A 029 997 21 48 .SEALING RING 001
71 A 007 993 28 01 .SPRING
43 MM 001
74 A 271 997 00 45 SEALING RING
COOLING WATER OUTLET 001
77 N 000000 0000092 SCREW
PIPE SOCKET TO CYLINDER HEAD
MBN 10143-M 6X110- 8.8 DBL9440.40 002
100 A 271 200 13 56 FITTING
CYLINDER CRANKCASE,RIGHT 001
103 A 007 993 28 01 .SPRING
43 MM 001
106 A 001 997 55 41 .SEALING RING 002
112 N 910143 3006003 SCREW
PIPE SOCKET TO CYLINDER CRANKCASE
M6X25 003
120 A 271 203 06 02 LINE
AT ENGINE CONNECTION [003]
001
122 A 013 997 98 45 .O-RING [003]
001
124 A 007 997 20 90 .CLIP
22/12 MM 001
126 N 910143 3006003 SCREW
COOLING WATER LINE TO CONNECTION FITTING
M6X25 001
128 A 006 997 42 90 CLIP
28/35 MM 001
130 A 271 200 14 52 LINE
AT CYLINDER HEAD 001
140 A 027 997 90 48 .SEALING RING 001
143 A 007 993 40 01 .STOP SPRING
8.8 MM 001
146 A 000 542 51 18 .SENDER UNIT 001
149 A 022 997 98 48 ..SEALING RING 001
152 A 008 988 91 78 .CLIP 001
160 N 910143 3006001 SCREW
LINE TO CYLINDER HEAD
M6X16 002
900 A 210 540 20 81 PIN BUSHING HOUSING
REFRIGERANT TEMPERATURE SENSOR
2 PIN;B11/4 001
901 A 000 540 23 05 REP.SET CONTACT
REFRIGERANT TEMPERATURE SENSOR
0.5 MM2 MQS;B11/4 [004]
NB
901 A 000 540 24 05 REP.SET CONTACT
REFRIGERANT TEMPERATURE SENSOR
0.75 MM2 MQS;B11/4 [004]
NB
901 A 000 545 68 80 SEAL
REFRIGERANT TEMPERATURE SENSOR
0.9-1.3 MM2;B11/4 NB

bigspender101

Thanks Glen M...Much appreciated...
Now you could really be my savior, if you had a diagram showing me how to take it apart.....LOL

Glyn M Ruck

I don't have but it's simple. Undo clips & clamps & flange & mounting torx bolts & it simply pulls off. You will need spare coolant for top up & check O rings.

scottonfire

DOES THE COOLANT HAVE TO BE DRAINED PRIOR TO REPLACING THIS HOSE #130??

slammer111

^ Pretty sure you don't have to. A pile of it will gush out of the part and the engine block once you break one of the seals. After putting everything back, just top up with a coolant mixture as needed to bring it back to the correct level.

When my coolant thermostat (located at a lower point on the engine) failed, that was pretty much the procedure. I just try not to think about all the fish I killed when all that coolant gushed out.

jkowtko

So I'm thinking I have the same issue ... however I have a nice white residue everywhere ... is this the dried coolant?

Thanks. John

VVF

Sure is... Search scottonfire's posts also.
Just your coolant is straw in color, that may affect the residue color.

The pipe goes for about $50 online, and of course $95 at my dealership
Part# is 271-200-15-52 (looks like it's been updated, hmm)

BTW John, have you flushed your coolant recently?
I am thinking this might be related to the hot-cold cycle it undergoes when flushing with a fresh batch of cold distilled water

jkowtko

Thanks for the quick reply. This doesn't look like a difficult job at all.

Regarding your question ... no ... the thermostat and temp sensor were replaced by the dealership maybe four years ago ... haven't touched it since. The last thing I did in addition to the oil change was the motor mounts and spark plugs, but that was still a few months back. Must just be age ...

Questions:

* does this part include the little seal 027-997-90-48? Or do I have to buy that extra?

* should I consider replacing any of the other pieces in this circuit while I'm doing this? Or is this one pipe the only failure-prone piece?

* when should I be considering replacing the water pump?

Fyi I'm at 120k miles right now.

Thanks. John

VVF

Hmm, yes, may just be the age and the location in close proximity to hot exhaust....

I believe it includes the o-ring (it should also include the temperature sensor), but I'd check with the dealer to avoid having to order separately.

Don't know about other pipes.

My water pump was making some faint metallic scraping noises at 142k when I had the belt off to refresh the belt + idler/tensioner pulleys. Now at 147k still doing fine.
So you should probably be fine for a couple thousand miles at least.

slammer111

Yes that's dried coolant. Looking at the pic, I'd be willing to bet you have the exact same problem I had last week - a failed coolant pipe socket.

When I started gradually losing coolant a few weeks ago, I just started topping up the coolant, but noticed the problem getting progressively worse. Finally I decided to open up the socket, and found that the pipe had snapped in half where the O-ring normally goes.

It's made of the same crappy plastic as the coolant breather pipe socket. I would recommend you change that part out if you haven't already done so, while your coolant is low. Otherwise you're going to have to top the coolant up yet again, and possibly get stranded if this part goes on you in the middle of the day. The part number for that is A003-997-06-89.

As usual, I recommend replacing all associated O-rings (part #s shown below) when replacing a given part. Last thing you want is to have to open everything up again because something else is now leaking. Do it right or do it twice.

You will need the following parts. Just buy EXACTLY what I've listed and you'll be golden. No more, no less.

Pipe socket A271-200-12-56 - this includes both the metal clip for the radiator hose end, as well as the O-ring that goes between this pipe and the engine block.
Seal ring A271-997-00-45 - fits between the socket end and the thermostat. I found a missing chunk in the pipe socket where that O ring goes, so mine was deformed/crushed when I pulled it out. Definitely couldn't reuse in my case.
Seal O-ring A026-997-68-45 - fits between the radiator hose and the socket.

Another (optional) item you may want to consider replacing is the coolant thermostat A271-203-05-75. This one seems to be hit and miss, but it died on my car after 8 years or so. If it fails, your car throws a P0128 error because the engine can't get up to the proper operating temperature. It won't leave you stranded though.

The dealer diagrams were a bit confusing, but this is all that you need. No need for the new metal clip, as the new pipe socket includes it.

Lastly, you'll need a jug of coolant. MB now has a new blue G48 coolant BQ-1-03-0004 that supersedes the older yellow G05 BQ-1-03-0002 formula. The 2 coolants are compatible, meaning you do NOT have to drain the old coolant to use the new. Remember to mix 50/50 with distilled water. The old stuff is still fine to use if you have any kicking around. New stuff is just more environmental friendly and has the same service life.

jkowtko

Geez, with all of these plastic pipes this engine is looking like a frickin' Habitrail ...

Okay I see your focus on the front pipe ... sounds good. Thermostat was replaced a few years back but I certainly don't mind replacing it again. In fact after 10 years I have no problem spending $200-300 in parts to replace all cooling related hoses, pipes and water pump. I'll start with the leaking areas and adjoining seals and clamps though.

* On your list of parts, "Seal O-ring A026-997-68-45 - fits between the radiator hose and the socket." does not show up on the diagram or parts list that Glyn posted. Is this a replacement for #68, "A 029 997 21 48 .SEALING RING"?

* Regarding the above, if I just buy a new thermostat then I will get both of these parts included?

* What about the rear spray area on the transmission bell housing. Is that still a faulty main coolant pipe A 271 200 15 52 ... ?

I still have to get out there an pull off the covers and check things out a bit more closely. Fortunately I have another car to drive so I can take my time to inventory the parts and get everything done as completely as possible.

Thanks for your help.

-- john
Thanks. John

jpman

bigspender101 the problem will go away by just replacing the seal (item #140 on Glyns diagram).

I had the same issue on my 05. It is a piece of cake to replace, you will need some coolant and distilled water to replenish/bleed coolant after some is lost.

If you chose to go with new pipe it does come with new seals and new temperature sensor.

slammer111

Jkowtko, the 68-45 part isn't in that diagram - it's in another diagram that shows the radiator itself as well as the connecting hose, as part #65 iirc (not to be confused with the #65 in the diagram Glyn posted, which shows the hose socket itself). This was the mistake I made (I omitted the #65 ring) that necessitated a return to the dealer. I'm trying to save you a trip. Work with me here.

The #68 ring you're asking about comes with the socket pipe, as well as with the thermostat. So if you buy both new parts, you'll have a spare. The thermostat also comes with a new seal ring #74, so you won't need to buy that separately if you're also replacing the thermostat.

jkowtko

I pulled off the air intake tube and the engine covers and took some more pictures ... what do you think? I think it's the water pump.

To me it looks like the usual water pump on it's way out. Leaks for a bit, then stops, then leaks profusely and drains your system. In this case it looks like it's spraying coolant around in the front a bit, then the coolant drips back along the lines to the rear of the engine where it drops off onto the bell housing.

I couldn't find a trace of anything on the front thermostat pipe -- it still looks new to me.

I also couldn't really find anything wrong with the cylinder head coolant pipe, or that return hose nipple.

I also tried warming up the engine for about a half hour (I topped off the reservoir with distilled water first) in hopes that I would see some coolant coming out somewhere. Nope. The thermostat opened at about the right time and the top radiator hose turned from cool to hot, right on queue. So the thermostat doesn't appear to be jammed. But no leaks anywhere.

I think tomorrow I'm going to wipe down the engine to remove all residue, then take it to work (about 7 minutes away) and check it there and check again after I return home, to see if I can spot any leakage.

But I'm thinking it's the water pump. Do you agree?