sullyj

Have a 2008 D3 4.2 with 176,000 miles. Engine warning light came on and scan determined there was a vacuum leak. Independent tech says it appears I need a new intake manifold because smoke test shows no leaks to be found anywhere else. Quoted $2500 for repair due to need for OEM intake manifold. Car seems to run fine as is, but I don't like driving it with a warning light on. Really considering moving on to another car given the mileage, but should try and locate a used intake manifold? I'm also due for upper/lower control arms which is another $2000-2200. At this point I think I'm just throwing money at the car because odds are I'm looking at another significant repair sooner than later. Any advice offered would be appreciated.

MP4.2+6.0

All of this sounds extreme to be direct.

Replacing intake manifold after a smoke test because "no leaks to be found anywhere else"? If literally true, how about plan B...look...again. How about, test any logical possible leak areas with some decent viscosity oil? How about, consider the arguably more likely possibility it is simply the o rings on the injectors? Thus same thing, try some oil on top of injectors and see what happens. Or, look carefully at the rear vacuum lines, connectors and fittings that ultimately drive power brake booster. Or the oil separator/PCV equivalent function, where some have seen issues. Or... In any case, if I read your post correctly and leak test inconclusive, throwing up hands and saying let's replace the most expensive possible part does not sound like great diagnostics to me.

Also, let me not skip past "scan determined..." What scan exactly? Can I guess an indy likely used a generic OBDII scan tool? If so, that's like using crayons for coloring on a diagnostic form with an Audi. If he actually had real shop equipment of the Snap on console or other varieties and had the car specific diagnostic packs for Audis/VW's, maybe. That is, if you have the scan equipment at the level either the dealers do or that VCDS contains, you can often get a whole lot more info than just some OBDII codes. Helps avoid the "throwing parts at it"/parts 'n' pray diagnosis, which seems like basically what you have.

As far as used intakes, good luck. The intake is a Rube Goldberg contraption almost designed to fail in long term with the internal flap set up. Doesn't mean vacuum leak BTW--failure is more likely mechanical internally--though another obvious place to check are at the end shafts of the internal flaps. Also look for signs of tampering if this was a used car with unknown history. That is, someone tried to open it before to get at internals like those flaps. But if you need one, from experience with my C5 4.2 (where manifold broke at flap bearing point after flaps froze), I never could find one used. including on the Euro eBay sites. As in, too many issues too many owners have, so it tends to be an in demand part. Compounded by yards typically wanting to sell complete engines so more likely to come from a blown motor wreck or wreck where motor itself was damaged, yet not in intake area. Even if nothing else, pulling your existing manifold for these kinds of dollars would be in order--after more and easier inspections are done--for a thorough visual of all sides/bottom, plus gasket integrity and such.

Control arms. That's a lot of $$$. Probably 90% of issues are primarily in upper arms, which are way easier to service than lowers. Failures/lots of noise even at OE are 50-100K, so you are way over that if never done before. Rubber bushings cost about $30 each for OE quality; need a press in that case, which a wheel and brake type shop probably has. Even if you replace whole arm with OE (Lemforder), those are around $500 for complete upper set from discounted indy parts places. Throw in some bolts and sway bar links and call it $600 in parts.

Find another recent thread on annual spending expectations. If you just want to drive into ground, budget lower. If you want to pass at least the no lights on dash test as you mention, plus presumably generally quiet and safe ride but not fastidious, expect more but generally in line with other Euro luxo rides. It is not a just add gas and oil type ride long term unless you want to let it go to seed, especially at 175K miles. As a 2008 though (post final facelift) and assuming a decent body and interior, it has some decent years and miles left.

BASARAB

I just paid close to $2k for 4 control arms with alignment and brakes all around (tetrax rotors and pagin pads)

sullyj

Thanks MP4.2 +6.0 for the very thorough feedback. The shop I use specializes in Audi's and particularly "S" and "RS" cars so I'm assuming they're using decent diagnostic equipment. The tech told me I also needed a PCV valve and he replaced same with hopes of the engine light issue getting solved. When I picked up the car two weeks ago he said "sorry, the issue doesn't appear to be the PCV valve" but when I started the car the engine light was off. I assumed he simply removed a code or something and the light would reappear in a day or two. I have driven the car easily a thousand miles since and the engine light still hasn't come back on and the car seems to be driving fine. I'm pretty meticulous about the car so the interior and exterior look great and I change oil (synthetic only) about every 4-5 thousand miles. Although I need the suspension work, the car drives fine and passengers always comment on how well the car rides. I want to find out if the motor is still running lean, but I'm afraid it may bring the check engine light back on if I do. By the way, for a second opinion I also took the to the "stealer"and their diagnostic result was a lean code for bank 1 and bank 2 with 172800 for check engine light on. Given your comments I may see if I can find a shop that can replace the bushings or just pay the price and replace the components needed. regardless, your feedback was excellent and appreciated.

Greg5OH

quick way to check for vacuum leaks. grab a cigratee/cigar w.e., get a mouthful of smoke and slowly blow it thru a hose around the suspect area with the engine at idle. You will quickly see even the smallest vacuum leaks this way.
after i split and resealed my manifold on the s8, i had vacuum leaks right at the corner. couldnt hear them, but the smoke test showed it quite clearly.

daudic

I have an 07 with 204k. I replaced the intake manifold myself from ECS Tuning at 155k because of the flaps. Cost me $1700 in parts. More now though. At 170k got the p0171 code. The local Indi shop said it's the intake manifold. I found out that the bolts loosen over time that hold it Dow AND hold it together. Had to remove them and use blue lock tight after replacing the metal gaskets. Still get the code and now the driver's side bolts keep loosening up. I also replaced the front upper control arms myself twice. Once again they rattle and creak after 15k.

aTOMic

You didn't use "Karlyn" brand UACs, did you?

MP4.2+6.0

1. Check motor mounts and the separate torque mount to see if broken, most likely torque mount which is near front U.S. passenger side corner of engine block--ahead of the main motor mount. I pulled my C5 A6 4.2 manifold twice and never had bolts backing out; thus I'm wondering if you have motor shake or something pronounced somehow causing them to loosen up. I always locktited mine. You can also chase the threads with correct size tap, and perhaps get new bolts in case threads basically got a little loose from rattling over long periods of time if they were loose originally.

2. Control arms: if basically any of the "bargains," cheap is cheap in multiple ways. Said another way, if other than dealer or Lemforder OES--both of which cost more--assume they were likely junk and now already showing it. Also, if you didn't do the sway bar links, by your miles that will be issue #2 in frequency. 100K is more like when they show issues. Can get a set of Lemforder OES's from rmeuropean.com in the $60 range, so inexpensive as well as easy to DIY install.

daudic

The last ones are Lemforder. Currently, only the driver side rattles and in warm/hot weather they creak.

MP4.2+6.0

Thus, with only 15K for now assume it is NOT the control arms... IF they were installed correctly and thus tightened under load and not when up in air. Then, repeating the balance: Sway bar links? Also check torque and motor mounts.

Add to it, alos check sway bar bushings themselves--not just the end links. It used to seem to be a first year teething problem with 2004's (2003 in Europe). But then there where a few 2005's. Recently had a 2007 where owner found they fell apart. Yours is a 2007...