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Discussion Starter · #1 ·
Could some kind soul take a picture of your coolant tank when you have a few minutes?

My coolant tank is clearly "messed up" but I'm not entirely sure as to the extent just yet. Looking at the top of my coolant tank it appears that a nipple was accidently or intentionally broken off, then a screw put in its place with RTV sealant or JB Weld. Similarly, there is another JB Weld plug on the side of the tank.

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As creative as these modifications may be, the one next to the cap is definitely leaking under pressure when at temperature. I'm replacing the tank for sure, but I'm trying to determine which additional hoses or clamps I need. I see 3 coolant hoses connected to the tank; two near the top of it and one at the bottom. Is this the correct number? I've been unable to source a good image of an intact tank and the best I have from my previous car is a shot of the entire engine bay:

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Discussion Starter · #2 ·
I did find these images from my service manuals, which seem to indicate that either 2 or 3 lines are connected to the tank. From parts diagrams, it appears the extra 2 (?) are just capped with short sleeves?

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The little nipples next to the cap are common failure points, I just replaced a tank in one of my W12s.

I don't recall all of the connections but I think there's the large one on the side with a smaller one above it and a small one on the top pointing rearwards. That's in addition to the two nipples next to the cap. Those are both used on the W12 but I think the V8 only uses I e of those

Btw, the coolant tank is available new and pretty reasonably priced.
 

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Discussion Starter · #4 ·
Yeah, for the price I'm going with a new tank that doesn't have almost 20 years of heating and cooling stress :)

Your description sounds accurate, so if I understand correctly I think I need a new tank, two new hose cap things, and two clamps to secure said hose caps. Sounds like the expected hoses themselves are present.
 
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Discussion Starter · #6 ·
I believe we've either got our wires crossed, or I'm not any good at counting. ECS has a decent picture of the tank in question: Search SiteSearch 3D0121407H - 3D0121407H - Expansion Tank - Primary (3D0 121 407 H) (ecstuning.com)

I count 5 outlets: 2 by the cap, 1 at the top rear (when installed), 1 large one at the bottom of the tank, and 1 slightly smaller above the large bottom outlet. The parts catalog seems to suggest that on your big 6.0's all 5 of these outlets have a connection: Volkswagen Phaeton (2002 - 2007) - Coolant cooling system. > ETKA Online > WebAutoCats.com

However, my car has only 3 hoses connected to the tank currently. This seems to be supported by the service manual diagram of coolant flow, and the parts catalog: Volkswagen Phaeton (2002 - 2007) - Coolant cooling system. > ETKA Online > WebAutoCats.com

The weird thing is that the catalog image seems to indicate there should be a hose on the smaller of the two bottom outlets, and nothing at the top two by the cap, but my previous car with an intact tank had a hose by the cap, as does the current one (both 4.2 V8's). However, another parts diagram indicates that the smaller bottom outlet is capped instead: Volkswagen Phaeton (2002 - 2007) - Cooler for coolant. reservoir. > ETKA Online > WebAutoCats.com

Based off numbers alone, I'm pretty sure that leaves two outlets to cap for the V8 engines. I'm fuzzy on which outlets exactly should be hooked up, but it may not really matter since it's just a tank with no pump or valves in it.
 
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I'm just going off my memory and you are probably correct. I do think there was a change between '04 and '05 V8s. My '05 has a small coolant line along the firewall that my previous '04 didn't have. Whatever lines you have will be obvious where to connect to on the tank and the rest gets capped.
 

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Discussion Starter · #8 ·
Interesting. My other car, which was actually a slightly later '04, had the BGH V8, but my current '04 has the BGJ. Both build data and serial numbers seem to indicate the BGJ-equipped car was built first, but that seems to contradict the "common wisdom" about the two engines. Both of my cars have had X9A "equipment options subset for USA" in their PR codes.

The VW service manuals indicate that the only differences between the two engines are that the BGH featured "European OBD" and lacked a leak detection system, while the BGJ featured "OBD II" and included leak detection. In my mind I don't understand how the BGH could then be sold in the US, but it's on the build sheet.

In the end, who knows. Coolant line changes may even have just been a mid-run update, like you suggest.
 
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The little nipples next to the cap are common failure points, I just replaced a tank in one of my W12s.

I don't recall all of the connections but I think there's the large one on the side with a smaller one above it and a small one on the top pointing rearwards. That's in addition to the two nipples next to the cap. Those are both used on the W12 but I think the V8 only uses I e of those

Btw, the coolant tank is available new and pretty reasonably priced.
I replaced mine a few weeks ago too with a new one. One of the hose nipples failed due to cracking. I had already replaced the auxiliary expansion tank about six months before after reading the posts on the forum about their proness to failure due to UV exposure. About a week ago the radiator developed a massive leak. So that's my next major operation 😄.

- Robert
 

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Discussion Starter · #11 ·
About a week ago the radiator developed a massive leak. So that's my next major operation
That sucks. I haven't looked into that procedure; how bad is it? I feel like there's a decent amount of room in front of my V8, at least compared to my BMW's. Those have all had straight-6's or the V10 and there is no free space under the hood at all.
 
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I replaced mine a few weeks ago too with a new one. One of the hose nipples failed due to cracking. I had already replaced the auxiliary expansion tank about six months before after reading the posts on the forum about their proness to failure due to UV exposure. About a week ago the radiator developed a massive leak. So that's my next major operation 😄.

- Robert
Seems like you are a few months behind my W12s in terms of having the same failures, albeit I didn't have the main radiator fail. Surprisingly the main radiator is not too expensive and actually cheaper than that small auxiliary one on the RH side.

Changing the radiator out is not too bad but you have to take the bumper cover off and put the front end into the service position.

Btw, make sure you check the new radiator closely for damages when you receive it. 73blazer and myself went through a total of 6 radiators before we received an undamaged one because of the lack of protection inside the shipping box.
 

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I had the front off last summer when I was working on the A/C. I have an entire front assembly spare. Meaning the carrier, fans A/C condensor and radiator. I only used one of the fans off that assembly as a replacement. I'll find out what a new one will cost me. Judging from the little country flag you're in Europe again, Stephan? 😄
 

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That sucks. I haven't looked into that procedure; how bad is it? I feel like there's a decent amount of room in front of my V8, at least compared to my BMW's. Those have all had straight-6's or the V10 and there is no free space under the hood at all.
It's not a complicated job. As I said in my reply to Stephan, I had the front end off last summer. Since I'm replacing the front bumper cover anyway as well as two new headlight units I'll combine the jobs. As Stephan wrote, the front end can be put in a service position using two bolt-in rods.

- Robert
 
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