Audi D3 A8 W12 coolant leak in front of motor; other noises
07-09-2015, 10:18 PM
#1
AudiWorld Super User
Thread Starter
Audi D3 A8 W12 coolant leak in front of motor; other noises
So, starting to post on my W12 water pump change saga. A combination of work write up, diagnostics, unexpected findings and preventative suggestions. Primarily meant for the W12 crowd and experts, but the odd A/C compressor findings could fit any of the D3s. Background is I have suspected a very slight water pump seal leak for a year or two. It arises from small drip marks/residue I find on the oil pan when I pull the belly pan off for other work like oil changes, and it seems to come from water pump area. But those accumulate over literally many thousands of miles between any under car work. No active leaks when running are visible and it rarely needs any coolant.
I went to do the job once before but ran into water pump screws I wasn't sure if I could tackle with tools on hand. I also found an apparent slight leak at an upper main hose that comes out of the thermostat that seemed to explain the issue the first time around. That was a simple std. Audi main hose o ring for a few bucks. That hose is directly above the water pump so I breathed some relief and closed it up. But then later I still found the slight drip signs. Darn.
Well, this time around the sound was suddenly bad--gravel stuff increasing with revs. Classic rapidly failing water pump bearing sound. At first I wondered about suspension compressor (given the constant posts on board...) before I opened the hood or did any closer look or try to track down sound since I would hear the noise at start up usually, but then I tied it to engine revs. No suspension arrow light show stuff either, and no history of any issues with the air ride stuff. Tying it to revs and seemingly water pump, that told me time to get at pump pronto. And later in story, that apparently wasn't it...yet again...
So, I start the tear down. This time, I decide with prior intake manifold and plug experience just to pull the intake for good work area access. For either newer W12 owners or the 4.2 group, this is of course a no timing belt motor, so you can also get to the thermostat or water pump in less than a full day (pre-FSI) 4.2 full timing belt job. Intake is also way easier to pull once you know the tricks than my C5 4.2 was from the several times I did it; it is magnesium and so weighs like 7 pounds even though it is like 18 by 24" nicely detailed metal. A few wire connectors, a handful of clamps, two air intake hoses and four oil vapor lines and 8 screws into the intake riser just below. Literally by 15 minutes in the intake is off and stored in trunk, and all is going well. Belly pan also off to drain some coolant at a few lines I know to open to do it more surgically. Yep, more coolant leaks on both oil pan and belly pan as usual. Check.
But wait, I go to disconnect my first trivia hose above the water pump area and it cracks open and spills coolant! (I had drained what I thought was enough to get to water pump bottom.) Huh? The little plastic T in the hose assembly basically falls apart. I find one side cracked open--where the coolant was leaking this time apparently, and as I went to get the overall hose component out (three small molded hoses with a T) another side of the T cracks in my hands. Definitely was on its last legs. See pictures of broken T and the hose area w/ part # still right there after 10 years.
So, first a general W12 upkeep note. Mine is 2006 delivered in late Spring 2005 (thus, 10 years old), 114K miles now. Previously several of us have found the coolant reservoir related plastic line that runs behind the motor gets brittle with time and is prone to crack/split. Thus, suggested maintenance by about 100K is to replace that line, which is somewhat pricy at a bit over $100. You can splice it w/ small diameter heater hose and clamps if it breaks as a stop gap--which I found dealer had apparently done at some service and never told me. Not good.
Well, now add to it this T up in front of motor. For W12 owners, it is where a line splits from a T and then one line goes to each head at a 90 degree curved metal fitting that is press fit into the heads. It is close to the motor (and thus heat soak) and very close to where the air pump related line across the upper manifold area is that you see as soon as you pull off the decorative motor/intake trim. Part 20 in the diagram below to be specific. Turns out this T is in the SAME reservoir bottle related line way at the other end from an early T near the reservoir. There are two small hose related set ups in the front of the motor. The first one (that didn't yet have issues) connects to that reservoir line set up where it tees by the fender and one part goes behind motor and the other toward the radiator area. That is part 22 in the diagram, and that T is right by where the "22" part label is; the part that cracks is where it extends toward a rubber hose in the upper left direction labeled 24. Some have also had issues with the next section of the plastic line (part 21) that runs toward the radiator and then connects to the unrelated hose assembly that is close to the upper radiator, part 5 in the diagram. The second hose set up where I had the issue (#20) then connects to that one at a Y and its two ends end up at the heads. The overall hose with the failed T is about $50 from audiusaparts so I just got the whole thing. But, it is a from Germany only part so I'm waiting still. Part 5 was available in the US warehouse BTW. From having cleaned out the T male nipples out of the hoses, I can see the plastic had basically fallen apart chemically or due to heat somehow. Didn't come out as fragments or a sheared off piece of plastic, but as kind of a mush. It also looks like it may be orificed or involve metered flow given how the T is sized down shape wise, so I went with straight OE replacement. My interim workaround is a $3.00 5/16" brass T from Amazon; 5/16" was the right hose fit for good clamping after some trial and error.
Meantime, the noise: no, not the water pump either! Instead, an oh $%$@ moment when I realize after I pull the serp belt that the AC compressor (!!) is sounding terrible when I turn the pulley in front by hand, and seems a bit distorted. And by contrast, I spin water pump and it feels normal--no noise, no obvious shaft play, no coolant leakage signs from bearing blow out areas. On the other hand, AC compressor is a serious front clip disassembly to get at most likely, plus refrigerant lines and all. I haven't done one in 25+ years.
Later, I am doing some general clean up in whole area with brake cleaner and spray around that pulley wondering what to think. Guess what, the gravelly sound and rough feel start to diminish! Yet more spray, and yet better. Hmmm, also fits with my noise observation that sound seemed to be at or near start up (and why I suspected suspension compressor somewhat too) and then faded--could have evaporated off, compressor worked through the minor deposits and settled down, etc. Having completed the clean up, feel is pretty normal to me, little play, and only minor noise left when I turn its pulley by hand and nothing like when I started the work or pulled car up on ramps as my wife says, "yes your car sounds terrible." Thus, working theory: coolant spray from line was getting at AC pulley/drive area--it's only inches away and belt travels whole area of course too. When coolant burns off it leaves that residue; I actually scraped some really hard deposits off a few of the channels on the main crank pulley that took a very sharp fine screwdriver blade to get off. Regardless, A/C compressor seems to check out physically so good so far; final reassembly not yet done so I have yet to start it. Serp belt is back on.
Net, seemed to let me off the hook yet again on the water pump, but I had now pulled enough that I thought I should see it through. I was also not 100% sure I had it tracked down to the broken T, since there was pink coolant deposits toward the drivers side of the water pump and block that could have come from hose, water pump bearing/blowout ports (though I really couldn't see any leakage in that area), or even the old main hose o ring minor drip stuff. I decided ultimately I was still going to finally install that (OE) water pump I had for some years...until I ran into the final lowest retaining screw for the water pump that then went down the what more can go wrong path... More to come, though largely now solved. I will leave this post specific to the front hose related findings.
For reference that hose assembly was marked 4E0 121 108F per the picture, and has since been superseded to a "K" suffix. Hopefully maybe a new and improved T component by chance?
I went to do the job once before but ran into water pump screws I wasn't sure if I could tackle with tools on hand. I also found an apparent slight leak at an upper main hose that comes out of the thermostat that seemed to explain the issue the first time around. That was a simple std. Audi main hose o ring for a few bucks. That hose is directly above the water pump so I breathed some relief and closed it up. But then later I still found the slight drip signs. Darn.
Well, this time around the sound was suddenly bad--gravel stuff increasing with revs. Classic rapidly failing water pump bearing sound. At first I wondered about suspension compressor (given the constant posts on board...) before I opened the hood or did any closer look or try to track down sound since I would hear the noise at start up usually, but then I tied it to engine revs. No suspension arrow light show stuff either, and no history of any issues with the air ride stuff. Tying it to revs and seemingly water pump, that told me time to get at pump pronto. And later in story, that apparently wasn't it...yet again...
So, I start the tear down. This time, I decide with prior intake manifold and plug experience just to pull the intake for good work area access. For either newer W12 owners or the 4.2 group, this is of course a no timing belt motor, so you can also get to the thermostat or water pump in less than a full day (pre-FSI) 4.2 full timing belt job. Intake is also way easier to pull once you know the tricks than my C5 4.2 was from the several times I did it; it is magnesium and so weighs like 7 pounds even though it is like 18 by 24" nicely detailed metal. A few wire connectors, a handful of clamps, two air intake hoses and four oil vapor lines and 8 screws into the intake riser just below. Literally by 15 minutes in the intake is off and stored in trunk, and all is going well. Belly pan also off to drain some coolant at a few lines I know to open to do it more surgically. Yep, more coolant leaks on both oil pan and belly pan as usual. Check.
But wait, I go to disconnect my first trivia hose above the water pump area and it cracks open and spills coolant! (I had drained what I thought was enough to get to water pump bottom.) Huh? The little plastic T in the hose assembly basically falls apart. I find one side cracked open--where the coolant was leaking this time apparently, and as I went to get the overall hose component out (three small molded hoses with a T) another side of the T cracks in my hands. Definitely was on its last legs. See pictures of broken T and the hose area w/ part # still right there after 10 years.
So, first a general W12 upkeep note. Mine is 2006 delivered in late Spring 2005 (thus, 10 years old), 114K miles now. Previously several of us have found the coolant reservoir related plastic line that runs behind the motor gets brittle with time and is prone to crack/split. Thus, suggested maintenance by about 100K is to replace that line, which is somewhat pricy at a bit over $100. You can splice it w/ small diameter heater hose and clamps if it breaks as a stop gap--which I found dealer had apparently done at some service and never told me. Not good.
Well, now add to it this T up in front of motor. For W12 owners, it is where a line splits from a T and then one line goes to each head at a 90 degree curved metal fitting that is press fit into the heads. It is close to the motor (and thus heat soak) and very close to where the air pump related line across the upper manifold area is that you see as soon as you pull off the decorative motor/intake trim. Part 20 in the diagram below to be specific. Turns out this T is in the SAME reservoir bottle related line way at the other end from an early T near the reservoir. There are two small hose related set ups in the front of the motor. The first one (that didn't yet have issues) connects to that reservoir line set up where it tees by the fender and one part goes behind motor and the other toward the radiator area. That is part 22 in the diagram, and that T is right by where the "22" part label is; the part that cracks is where it extends toward a rubber hose in the upper left direction labeled 24. Some have also had issues with the next section of the plastic line (part 21) that runs toward the radiator and then connects to the unrelated hose assembly that is close to the upper radiator, part 5 in the diagram. The second hose set up where I had the issue (#20) then connects to that one at a Y and its two ends end up at the heads. The overall hose with the failed T is about $50 from audiusaparts so I just got the whole thing. But, it is a from Germany only part so I'm waiting still. Part 5 was available in the US warehouse BTW. From having cleaned out the T male nipples out of the hoses, I can see the plastic had basically fallen apart chemically or due to heat somehow. Didn't come out as fragments or a sheared off piece of plastic, but as kind of a mush. It also looks like it may be orificed or involve metered flow given how the T is sized down shape wise, so I went with straight OE replacement. My interim workaround is a $3.00 5/16" brass T from Amazon; 5/16" was the right hose fit for good clamping after some trial and error.
Meantime, the noise: no, not the water pump either! Instead, an oh $%$@ moment when I realize after I pull the serp belt that the AC compressor (!!) is sounding terrible when I turn the pulley in front by hand, and seems a bit distorted. And by contrast, I spin water pump and it feels normal--no noise, no obvious shaft play, no coolant leakage signs from bearing blow out areas. On the other hand, AC compressor is a serious front clip disassembly to get at most likely, plus refrigerant lines and all. I haven't done one in 25+ years.
Later, I am doing some general clean up in whole area with brake cleaner and spray around that pulley wondering what to think. Guess what, the gravelly sound and rough feel start to diminish! Yet more spray, and yet better. Hmmm, also fits with my noise observation that sound seemed to be at or near start up (and why I suspected suspension compressor somewhat too) and then faded--could have evaporated off, compressor worked through the minor deposits and settled down, etc. Having completed the clean up, feel is pretty normal to me, little play, and only minor noise left when I turn its pulley by hand and nothing like when I started the work or pulled car up on ramps as my wife says, "yes your car sounds terrible." Thus, working theory: coolant spray from line was getting at AC pulley/drive area--it's only inches away and belt travels whole area of course too. When coolant burns off it leaves that residue; I actually scraped some really hard deposits off a few of the channels on the main crank pulley that took a very sharp fine screwdriver blade to get off. Regardless, A/C compressor seems to check out physically so good so far; final reassembly not yet done so I have yet to start it. Serp belt is back on.
Net, seemed to let me off the hook yet again on the water pump, but I had now pulled enough that I thought I should see it through. I was also not 100% sure I had it tracked down to the broken T, since there was pink coolant deposits toward the drivers side of the water pump and block that could have come from hose, water pump bearing/blowout ports (though I really couldn't see any leakage in that area), or even the old main hose o ring minor drip stuff. I decided ultimately I was still going to finally install that (OE) water pump I had for some years...until I ran into the final lowest retaining screw for the water pump that then went down the what more can go wrong path... More to come, though largely now solved. I will leave this post specific to the front hose related findings.
For reference that hose assembly was marked 4E0 121 108F per the picture, and has since been superseded to a "K" suffix. Hopefully maybe a new and improved T component by chance?
Last edited by MP4.2+6.0; 07-10-2015 at 08:11 AM.
07-10-2015, 06:54 PM
#2
AudiWorld Super User
Great write-up MP. These darn German cars and the labyrinth of small hoses and plastic pipe fittings. But when you fix any issue and take if for a ride, it sure makes it worth the effort.
You know, I hear they're putting computers in cars these days too
You know, I hear they're putting computers in cars these days too
07-10-2015, 07:43 PM
#3
AudiWorld Super User
+1. thanks for the info. I don't understand the extensive use pf plastics for cooling system parts on all German makes. We routinely get VWs, BMWs with over 100K miles and you just have to replace all the plastic cooling system parts. If you only replace the part that's leaking, you chase a leak until all the parts are replaced.
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