Repokidz73

Evening to all you members. I am praying someone can help me with my problem. I am having issues with my 2006 Audi A8L W12 popping the top radiator hose of under load. Any advice would be grateful.

MP4.2+6.0

Never on mine, zero. 175K, 2006 W12. Do you mean the hose right near center of motor seen in front of it? That one goes down to thermostat, which is then an obvious suspect Or maybe you do mean the one toward left side as you look at motor and goes to top of radiator? Has some other small auxiliary hoses that merge in to it with Y connectors. I have replaced both over years (true radiator one just recently) as a preventative, but neither failed. A small T on upper hose assembly did rot out 5 years ago. Beware BTW, there is an obscure 2006 W12 VIN split parts change on that true upper radiator hose and it is "no longer available" if the early one like mine. I got it as new old stock from Lithuania via EBay.

Both these hoses use a modern quick clip set up to make them removable without taking a lot of stuff out. The clip itself is a stainless steel piece of wire like a big paperclip that engages in a groove then it is locked and holds hose on. There is a related o ring inside the same fitting. If those hoses are not driven hard home and that clip then seated properly, it would pop off. If o ring is new, it is harder to refit too; simple silicone or soap wiped on helps. You can undo clip and thus main hoses with a flat screwdriver on the closed end side of the clip (the open end slides inward toward center of fitting as you free it up). The retaining clip can also be dislodged, or screwed up I guess by someone not familiar with them. Was any work done in same physical area that might implicate these hoses? Thermostat, water pump, front end body or USA passenger side headlight? fan assembly? radiator replace? other hose replace?

Repokidz73

Thank you for the quick reply. It’s the hose on the passenger side next to the inlet for fresh air to the filters. Goes from top of radiator on passenger side to a pipe on side of motor. Then there’s 2 additional hoses that go towards the middle front of motor just behind hatch

MP4.2+6.0

Yep, so that is true upper radiator hose. Follow prior reply guidance about how its clip locks. If that clip fitting is somehow broken, besides the Lithuania source if you have an "early" 2006 W12, you can probably just get the fitting for hose end from dealer as a stand alone part. To one clear, the fitting is sold with the whole hose assembly normally, and the hose itself only comes w/ fitting. When fitting is bought separately, then you clamp the hose to the new fitting part. Factory uses a permanent band clamp there you cut to fit new end piece. If it separated at that band area by chance, that suggests a deeper problem with cooling system, unless it was an already replaced end and replacement clamp was not tight enough. FWIWy you can get the o ring that goes inside it as piece parts too. I change them when I pull and reuse a hose like this.

Was any work done in this area that would explain why it pops off? 99% of time I see something unexpected like this on W12, some prior work error explains it, whether last week or years back. People who are competent to work on it deep in are few and far between. Having recently put the new hose in, it is certainly possible to think you got it locked in, but not true. You yank on it fairly hard once seated to be sure. I assume cooling system is operating correctly--temp gauge warms and stays centered more or less, fans come on when engine gets hot (besides the A/C related fan function). If not and it is overpressurizing/boiling over, that needs attention. Hoses will start to blow at 18 years old, cooling reservoir bottle rupture, etc.

Most W12 hoses now...if available...seem to come from Germany. So expect a likely 2-3 week lead time. Similar at that point to the Lithuania type Ebay OE ones. You really need part #'s though to buy that way, and the 2006 model year is hard to sort that VIN split. It does affect this specific hose.