A4 Rattle with Brakes Applied?
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 363
From: Midland TX
A4 Rattle with Brakes Applied?
I have a 2001 and I am not so sure the car has not always behaved like this, just wondered if it was normal? Most of the time when I come to a complete stop (like at a red light) and the car is still in Drive, it will start rattling (more like a stumbling sound) underneath. If I let up in the brake momentarily it will stop, but usually starts again after a second or so. It happens both with and without the A/C on.
Does anyone else experience this? What would cause this? Maybe the idle is set too low?
Does anyone else experience this? What would cause this? Maybe the idle is set too low?
Last edited by Choreo; May 21, 2008 at 02:41 AM.
Instructor
Joined: Mar 2008
Posts: 152
Likes: 0
From: Topeka Kansas
I too experience this but it seems to be really subtle. It happens most of the time when i'm backing up and applying the brakes. It isn't really bad but I can still feel/hear it. I also would like to know if there is anything I need to tighten or fix. Mine is a '98 A4 with 50K miles.
Drifting
Joined: Jul 2000
Posts: 1,521
Likes: 20
From: Knoxville TN
My 01 has started doing this also. I have noticed that if I put it in neutral or hold the brake and bring up the engine rpm it goes away which has lead me to think it was the exhaust rattling at that particular RPM. So I think I will check my exhaust support springs! Hopefully that is the problem.
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 363
From: Midland TX
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 363
From: Midland TX
Have some more info on what I am experiencing...
I noticed today that every time this vibration occurred, the RPM dropped to 400 RPM at a stop? It normally idles in Drive at 500 RPM. When I first start the car and put in in Drive or Reverse, this stumbling usually occurs and every time the RPM dips below 500. Usually if I just let up on the brake and let the car roll a few inches and reapply the brake the vibration stops, but the Tach also goes up to 500 RPM.
So I guess the big question is "Why is my car wanting to drop below 500 RPM at almost every stop and start up (85% of the time)? What can be done to keep the RPM above 500?
I noticed today that every time this vibration occurred, the RPM dropped to 400 RPM at a stop? It normally idles in Drive at 500 RPM. When I first start the car and put in in Drive or Reverse, this stumbling usually occurs and every time the RPM dips below 500. Usually if I just let up on the brake and let the car roll a few inches and reapply the brake the vibration stops, but the Tach also goes up to 500 RPM.
So I guess the big question is "Why is my car wanting to drop below 500 RPM at almost every stop and start up (85% of the time)? What can be done to keep the RPM above 500?
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Pro
Joined: Mar 2007
Posts: 600
Likes: 11
From: Wilmington NC
I had the same problem and it drove me mad!
My problem was a loose heat shield in the rearend. I had a gear swap and it didn't get tightened down all the way. Sounded like my exhaust was loose and bouncing up and down. Found it and took less than a minute to fix. No more problems!
My problem was a loose heat shield in the rearend. I had a gear swap and it didn't get tightened down all the way. Sounded like my exhaust was loose and bouncing up and down. Found it and took less than a minute to fix. No more problems!
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 363
From: Midland TX
I had the same problem and it drove me mad!
My problem was a loose heat shield in the rearend. I had a gear swap and it didn't get tightened down all the way. Sounded like my exhaust was loose and bouncing up and down. Found it and took less than a minute to fix. No more problems!
My problem was a loose heat shield in the rearend. I had a gear swap and it didn't get tightened down all the way. Sounded like my exhaust was loose and bouncing up and down. Found it and took less than a minute to fix. No more problems!
Is there a voltage regulator somewhere? Could it be the PCM?
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 363
From: Midland TX
I just had the Dealership swap my steering wheel about a month ago when they installed my VetteEssentials wheel. That involved pulling the air bag so I imagine they unhooked the battery and just did not get it back tight (I have never seen anyone actually use a torque wrench on a battery).
In any case thanks for the tip!
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 363
From: Midland TX
Well at least narrowing it down I think. Had a little bit of stumbling today but now the turn indicators are blinking really fast at times (hyper-flashing). I have Halos in the rear, but first time I have experienced this. One thing is for sure the Voltmeter in the car is dipping down below 13 quite often - especially when stopped, so I am going to have them check the battery tomorrow. It is a 3 year old Red Top. If that shows good, I guess the alternator is next (37,000 miles).
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 363
From: Midland TX
Well battery tested "OK". Unfortunately, the alternator failed the test - "Regulator Output Low". Maybe I will get lucky and this will be covered by my GMPP Extended Warranty since a new one is over $400!
Racer
Joined: Sep 2006
Posts: 280
Likes: 0
I had a similar problem a year and a half ago and turned out to be a bad alternator..........awful rattling noise when the car is idling......so I think you've solved it. While you're at it swap the belts for goodyear gatorbacks.............
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 363
From: Midland TX
MONDAY - Went to Dealer to get problem diagnosed - they agreed it was the Alternator and ordered one overnight.
TUESDAY - I went in to get alternator replaced, but the alternator that came in was cracked, so they reordered another
WEDNESDAY - Went in for 2nd appointment to get alternator swapped, but part did not come in.
THURSDAY - 3rd try - New alternator came in and got it installed (Made in France model?). That apparently fixed my problem! Car now idles beautifully at a red light. For over a month it felt like the car was going to fall apart just about every time I came to a stop - I never would have guessed an electrical problem. Felt like what I would imagine a bad torque tube bushing to sound like (but only at idle). Car now idles at 500 RPM without the 100 RPM occasional drop. Happy days!
TUESDAY - I went in to get alternator replaced, but the alternator that came in was cracked, so they reordered another
WEDNESDAY - Went in for 2nd appointment to get alternator swapped, but part did not come in.
THURSDAY - 3rd try - New alternator came in and got it installed (Made in France model?). That apparently fixed my problem! Car now idles beautifully at a red light. For over a month it felt like the car was going to fall apart just about every time I came to a stop - I never would have guessed an electrical problem. Felt like what I would imagine a bad torque tube bushing to sound like (but only at idle). Car now idles at 500 RPM without the 100 RPM occasional drop. Happy days!
Last edited by Choreo; Jul 10, 2008 at 07:51 PM.
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 363
From: Midland TX
Well, it was fun while it lasted...
I drove around for about an hour tonight and while the stumbling only started to come back at one red light (after about 45 minutes of perfect behavior), I noticed that the Voltage was slowly swinging from 11.8 to 13.2 on the digital readout (which I am assuming is not good).
All I can figure now is that the battery is bad (3 year old Red Top) even though it tested to be good on the bench last week or there is a harness or ground problem? Is there one ground location in particular the corresponds with the alternator?
I drove around for about an hour tonight and while the stumbling only started to come back at one red light (after about 45 minutes of perfect behavior), I noticed that the Voltage was slowly swinging from 11.8 to 13.2 on the digital readout (which I am assuming is not good).
All I can figure now is that the battery is bad (3 year old Red Top) even though it tested to be good on the bench last week or there is a harness or ground problem? Is there one ground location in particular the corresponds with the alternator?
