Noticed a sluggishness in performance but no engine codes to point to anything in particular. Yet there was a fairly obvious drop in performance. Turns out there are a couple of vacuum activated devices that open and close the air flow to the intake manifold. When they break and they will, performs decreases rather significantly as the engine can't breathe the way it was intended. The fix changes the performance enough to put a smile back on my face and reinforced why I love these cars. My 2006 A8 (4.2 US version) has gone through a couple of these factory supplied intake manifold vacuum devices and links. They were replaced under the extend warranty at about $400 each. This time, so I don't need to worry about them again, I replaced them with metal aftermarket links from gurenparts.com

Audi/VW 4.2 V8 Intake Manifold Linkage Arms - Gruven Parts

My set up required the short links, described as 1 inch for the A8/S8, if needed, confirm the size before ordering. There were just under $90 delivered, which isn't cheap but much better than the factory solution.

Here's a picture of the broken links, located at the front/top of the engine beneath the V8-4.2 logo plastic cover. Installation is straight forward, just took a bit of careful tugging on the broken plastic parts to get them off the ball joint. Be careful to support the plastic arms or diaphragm portion of the assembly to not break or damage them when pulling off the broken plastic links.

Like I said, very nice performance enhancement and improved fuel efficiency when the intake manifold is working properly. I hope others find this information helpful and inspire others to contribute their experiences in keeping our cars running their best.

 

Nice, gonna take a look at mine now. 👍

 

Yes, me too! Never thought of such!

 

Suggestion: make sure if these are broken that there is not an issue with the manifold. I view broken links as more a symptom than the long term issue.

Having dealt with it on my 2000 A6 4.2, the manifold design is sub par reliability wise. The problem is inside the manifold the seals are not sufficient longest term for the PCV valve water and oil fine emulsion that runs through any intake. On a port motor,the fuel spray cleans this stuff up at the valves, but not in the middle of the intake. It can slowly freeze up those bushings that the butterfly plates move on inside the manifold housing which in turn control the variable intake air flow stages. Then the rods can break--thus the "symptom" of the issue underneath. Little you can do beyond externally lubricating the mechanism with a penetrating oil, but that won't really get to the inside.

If goes like my C5 4.2 did, they can eventually freeze up fully. That's what mine did a few years after I first caught that the action was stiff--15 years out at 145K mile in that case, on a car with a lot of short drive cycles over the years. My plastic rods had not even broken when I caught that during a coincidental deep engine work dive. Then if you try to disassemble the main metal axial shaft at the core of the mechanism as things get worse the surrounding pot metal likely falls apart. BTDT. And then, you look on eBay after finding they cost $1000 +from the dealer...discounted...and come from Germany. Then you find 50 people before you already had the issue and none are available used that fit your now older motor, including even on the Euro eBays.

Thus, lube and maintain as best you can, early and often. And if you are in the market for a used 4.2, visually and functionally inspect the mechanism if possible. As OP said, it doesn't show up as any code in a scan. If you drive one and know the feel, if working correctly you may also be able to feel the power surge as it cuts to the high RPM tract--kind of like old secondaries on a 4BBL from yesteryear. If it's frozen or really stiff either open or shut, it doesn't have that step in the torque curve as the intake cuts from the long to the short runners.

 

Guess I need to look at my 2004 build with 85,000 miles. By pulling the front cover can I check the movement on the flapper arm?
Plan on an oil change tomorrow. Will look at this. If stiff will lube with spray lubricant. My car has been making a lot of short trips (

 

Very interesting, Galco. Thank you!

 

Yes, they can be moved manually. Like a mechanical throttle plate there is some spring pressure you need to overcome, and the available lever arm there is pretty short.

 

Good suggestions/comments form MP. To confirm the links didn't break due to a frozen or stiff mechanism, I also recommend you verify that the arms (not links) move freely and don't bind up from a stuck or gummed up bearing. Mine were smooth and functional and the plastic links seem to give up due the heat and over time simply fail. There is a DIY tutorial on the website if you have an issue with the bearings behind the arms, if you need to go that route. For me, it was just the links as i didn't even bother with the optional metal spring loaded arms available through GruvenParts.com as they were operating freely and appear to be in good shape.

For those with issues with the bearing sticking or not functioning smoothly, below is a link to the DIY, its for a D2 4.2 but as you'll see its very similar to the D3 4.2. Again, I didn't go this route as the arms moved freely and there was no binding of the bearing behind the arm inside the intake manifold. Lube may be an option as MP noted to avoid opening these bad boys up.

https://store-lyr7tp5r.mybigcommerce...e_Link_DIY.pdf

 

Checked the arms on mine and they rotate smoothly. The driver side seemed stiffer, may have been access issue.
Lubed good, will check at next oil change. Did see antifreeze on the outside of the overflow tank. And level a little below minimum. Think a tank replacement is in my future.

 

Guys,

Thanks for this thread, we appreciate the feedback here. Im Paul from GruvenParts.com btw. Its good to be on this forum finally.

Note that our billet linkage arms do carry a lifetime warranty, and while its unlikely you would need it, know that you have it (and we have been around for over 15 yrs and will be around for many more). Very good input here regarding this system and how well it functions. Be aware that even in a perfectly functioning intake system, these links will eventually break (just like the OP's). The reason is because the plastic linkage arms cure in the engine heat. Over time, the plastic links loose their ability to "flex" and become very brittle. This is a normal process that occurs to plastics when subjected to repeated heat cycles. The heavy return spring puts these links in tension, and they snap as highlighted in the OP pic.

Our links milled from wrought 6061-T651 aluminum will not be affected by engine heat, and therefore are suited to the task. If you are going to keep the vehicle very long, replace the plastic versions with our upgraded 6061-T651 versions. And yes, keep close tabs on the ability of the pivot levers to freely rotate as they can bind up and require internal cleaning - someone already posted the excellent DIY link, its on our product page for all to reference.

Also, as someone mentioned below, we do have the billet pivot levers for these engines. The product page will be updated soon to reflect the 2 styles of pivot levers, so if you need those in the meantime just call or email me. In the OP pic you can see he is using the SHORT links, and his car came with the LONG pivot levers. There is also a short pivot lever used on some vehicles. If you break the pivot levers, I believe VW/Audi requires your 1st born, so just know that we do have billet replacements available, also with a lifetime warranty.

Glad to be on this forum, please let us know what else we can make for these great vehicles. Here is a running list of what we make thus far for them, would love to get more in the works!


Audi/VW 4.2V8 Intake Linkage Arms !


Audi/VW 4.2 V8 Intake Manifold Pivot Levers !

GruvenParts.com 4.2L V8 Intake Manifold Linkage Arms and Pivot Levers : Warranted for Life ! Audi/VW P/N 077-198-327A (077198327A)


Billet Aluminum VW/Audi 4.2L V8 Oil Cooler Tubes !

GruvenParts.com is happy to announce this LIFETIME WARRANTED latest billet release for the Audi/VW 4.2L V8 engines with oil cooler pipe P/N 077-117-411A (077117411A).


Billet VW/Audi 4.2L V8 Oil Filter Housings !

Special Pricing in Effect ! Precision Machined Aluminum Oil Filter Housings For VW And Audi 4.2L V8 Engines !