Suspension Rattle, Left Front

[B727]

It starts. 43,000 miles, rattle left front over sharp-edge bumps, potholes and the like, heard more than felt, rattle continues for a split second after clearing the bump (I guess that pretty much is what a rattle is, isn't it). Suspension and steering feels tight and responsive otherwise (updated DRC installed). Haven't had a look but I think I understand what the possible causes could be. May just order up all arms, ARB bushing/link, spring mount rubber, since will need them sooner or later anyhow and would like to accomplish whatever job it turns out to be this weekend. Question, though, can the spring mount rubber be replaced without disconnecting the DRC? I'm thinking there should be enough slack in the lines but thought I'd ask. TIA

[Other_Erik]

May be sway bar bushings - I ended up going Hotchkis when I had some noise going over bumps. When I pulled the stock sway, the rubber bushing was dried and cracked, and the end of the sway bar itself was cracked, had almost clean broken through. Bonus, the thicker and more solid Hotchkis sways help eliminate body roll, so you get a two-for-one of not stressing your other suspension components as much.

Sorry, can't offer advice on anything DRC related as P/O of my beast replaced it with KWV3's.

O_E

[B727]

Thanks for that, would be nice if it's that simple. Driving home last night I was able to aim for a couple of rough sections on the interstate I usually try to avoid and no rattle at all, completely silent. So whatever piece has the slack, it is being taken up when under constant load. I thought I had eliminated caliper rattle as a possibility but maybe not. Unfortunately, won't be able to troubleshoot further until this weekend. Work really gets in the way of what's really important, damn it :-)

[cruzanrs6]

So I too had annoying rattle coming from the driver's front side. My scenario was the rattle was more prominent in colder weather. I live in Oregon, so the temps needed to be in the lower 40's or under for the rattle to really show up. I suspected a busing in the control arm system - and in the cold temps the material would in theory be more "stiff". Any way I wound up replacing all the control arms - some did have cracked/split bushings. Well that did not solve the problem. I went through everything and found all to be tight. I had 2 independent Audi service groups look at it - both could claimed they could not hear it. I finally took to the one of the dealers and finally after several days and finally leaving the car out in the cold over night - they heard the rattle. They suspected the DRC. So while no leaks could be seen any where - they decided to drain the fluid and refill the system. This resolved the issue. The DRC was replaced under the recall back in 2009 - since then the car accumulated about 35K mi. The service was $436 ($396 labor + $40 in new hydr oil).

Good Luck -

[B727]

After poking around pretty thoroughly, based on cruzanrs6's note (and other, similar stories out there) I'm thinking it is the DRC. No obvious problems with it, no leaks or weeping, but it was warmer this morning compared to last week and the rattle was greatly diminished. Given that it seems fine otherwise, I'll probably have the system recharged rather than replace them.

While I was under there, I changed a leaking central diff output shaft seal and the engine oil, so all in all a fun weekend.

[Dmb408]

Every time I always thought a sound was something else, it was unfortunately the DRC. Check for leaking at the accumulator lines by the exhaust and at all four corners (the struts).

[orcars6]

Interesting posts with the rattle. Ok. So, Northern Cal. has had some serious rains last 2 weeks and on 2 distinct occasions and only and when on freeway/ highway speeds and exit/ on ramp etc. at speeds over 50mph and well into 80mph the car has a simultaneous rattle and heavy almost water logged sound in the exhaust which all seem to come from just under and slightly behind drivers seat area- checked sway bars/ check tires/ wheels/ brakes and nothing- once rain subsides car is quite and normal.

After a week of silence it did it again this past weekend while driving in a heavy down pour??? Is it possible water is being trapped somewhere and resonating this muffled water logged sound from the exhaust as well as a clear heaviness rattle wobble coming from below the drivers side???

Any similar issues with you all???

[Bigglezworth]

Can only be 1 of four items. Some will 'rattle' while some will 'clunk'.

Check your sway bar bushings AND ensure all of the bolts for the end links are tight and torqued to spec.
Check your control arms. Uppers wear out 3:1 ratio to that of the lowers. Usually provide a clunk vs. rattle. Ensure all of the bolts for control arms are tight and torqued to spec.
Check your outer tie rods for movement.
Check your strut. Even if you have a Gen 2 DRC update, it's more than plausible you have a bad strut. Visual inspection would show wetting on either the strut of the flexible line itself. Pressure testing is as simple as pushing down on the corner of the car and seeing if it bounces slightly upon rising, or dampens immediately. The latter is good, the former is bad. Failed circuit on the DRC will provide a corner-to-corner instability when braking - Obvious IMO.

[orcars6]

Bigglezworth, have you accounted for the 'only when it rains hard' factor? Appreciated!

[Bigglezworth]

Question, though, can the spring mount rubber be replaced without disconnecting the DRC? I'm thinking there should be enough slack in the lines but thought I'd ask. TIA

Yes. You can in fact swap springs without discharging the system, but you must provide appropriate support for strut to hang outwards on the top while still resting close to position at the base. Remember you can leave the strut bolted up to the lower control arm, and once you unbolt the sway bar end links and unbolt the upper control arm frame mounting bracket, the assembly drops low enough to let the top part of the strut rotate out past the edge of the fender for service. It's fussy, and most won't attempt it, but it can be done if you're adament you need to do such.

[B727]

Thanks, as it turns out the rubber is perfect as is everything else. Started rattling again even on a warm day. It's weird how it's inconsistent. It sounds like something heavy rattling back and forth over about 1/4" distance. Kind of reminds me of a 1970's Chevy van with bad bushings traversing rail road tracks, if you can picture that. Will probably replace the upper rear link, nothing obviously wrong with it but that's the easiest place to start, and taking things apart may show me where the real culprit is (if that's not it).

[B727]

Started putting together a DRC recharge system, will come in way, way under the $1,650 Snapon wants for the complete dealer system. Did spring for the Snapon 6209/6 adapters, finding correct fittings always drives me batty. Also found a NOS damper (latest P/N) for $85 should it be needed. Hopefully she'll be back to perfection soon.

Doesn't look too challenging all in all, but any advice welcome from those that have tackled this at home.

[GreggPDX]

Subscribing, I'm interested in how hard it is to do a DIY recharge. If you Google "diy drc recharge", you'll find some links to discussions about it.

[Dmb408]

There is someone who did it (first I believe) on RS246.com, just do some googling, you'll find it. Key is to properly bleed and then fill slowly. Even the Audi procedures (the PDF) I believe are out there on the net.

[B727]

Yeah, even a guy who had success (got lucky may be more like it) without first evacuating the system. Only thing that has me (a little) worried is the fragility of the quick-disconnect fittings. Seems like it may be smart to have a couple on hand, but they're pricey ($200+).

[B727]

Zero pressure, nada, zip. I'm surprised that the clunk over sharp dips was the only real issue. Pumped it up with my home brew setup and now perfectly well behaved. No obvious leaks so far, so I'm hopeful whomever serviced it last just didn't know what they were doing.

My set-up is pretty much exactly like the person on RS246.com, refrigeration manifold, porta-power pump, and the Snapon adapters (Easy to come up with something else, but it was nice not having to figure that part out.) I used an electric vacuum pump. The refrigeration hoses are not ideal; they expand quite a bit, which makes judging whether the accumulator is shot impossible. I just chose to believe that it was fine.

PS, like all the tar? Thank you local metro district.

[B727]

After a week of silence it did it again this past weekend while driving in a heavy down pour??? Is it possible water is being trapped somewhere and resonating this muffled water logged sound from the exhaust as well as a clear heaviness rattle wobble coming from below the drivers side???

Any similar issues with you all???

So, yeah, today extreme downpour in Denver area and yes, heavy, throaty exhaust sound (actually sounded pretty cool) and vibration felt in the steering wheel. Pretty clear that the exhaust is being quenched by the heavy spray and making contact somewhere. Funnily enough, my 2.7T (w/ 3" DPs) did the same thing.

[nubcake]

So, yeah, today extreme downpour in Denver area and yes, heavy, throaty exhaust sound (actually sounded pretty cool) and vibration felt in the steering wheel. Pretty clear that the exhaust is being quenched by the heavy spray and making contact somewhere. Funnily enough, my 2.7T (w/ 3" DPs) did the same thing.

Mine touched the chassis with the "clamp" bolts - where downpipe and mid-muffler tube meet.