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View Full Version : '96 A4 2.8 Quattro -- noise diagnosis



mr72
12-02-2013, 09:23 AM
I am trying to get a handle on the myriad of stuff wrong with my daughter's '96 A4. It's a 2.8 V6 Quattro with 5 speed.

Right now, besides having a stuck-open thermostat (AFAICT), it also has a couple of noises that might be related.

1. when releasing the clutch or going from decel to accel, there is an audible "clunk" coming from the rear somewhere that you can feel in the chassis. Feather the clutch just right and you can avoid this.

2. on deceleration, only while in gear with the clutch out, normally with higher engine-braking loads, there is a non-rhythmic noise coming from the front right. It sounds like something whacking a piece of sheet metal, goes kind of "pop---a-pop-pop---popity--pop", but it's not so much a pop sound as it is a smacking/whacking kind of noise. Like if you took a chopstick and whacked it on the side of a steel garbage can. It's not a rhythmic clicking or related to engine or vehicle speed. It is no different whether turning or going straight. It can be heard best with the windows down.

Any hint to what these might be? Where to look? Hopefully they are both the same cause... ?

Cgoon009
12-02-2013, 02:28 PM
Video us brah

Videos are super helpful with this sort of thing. If you can upload one, that would help alot.

walky_talky20
12-02-2013, 02:44 PM
So while the car is making the decel noise what happens if you:

A) Clutch in and coast
B) Touch the brakes softly

Also, kudos on getting your daughter to drive a 5-speed. Can I have her number?

I kid, I kid.

mr72
12-02-2013, 03:46 PM
So while the car is making the decel noise what happens if you:

A) Clutch in and coast

The rapping noise goes away... it only makes this noise when the clutch is engaged (pedal out, engine braking) and decelerating in gear. Doesn't make the noise accelerating or cruising, or really if you are going very slow like 1st gear under 10mph near-idle coasting. It doesn't make any noise at all if decelerating or coasting in neutral or with the clutch pedal on the floor.

The other noise, the clunk is, of course, mostly on release of the clutch during upshift.



B) Touch the brakes softly


No change in the rapping noise, no matter how much braking, be it none or hard braking. No change in frequency, pitch, or anything.

At first I thought it was just a rattle. Like I could imagine a loose or bent exhaust heat shield rattling on something on decel if the engine mounts were allowing the engine to rotate a little bit so that an exhaust heat shield could touch something else. If there was a square millimeter of empty space under the hood of this infernal car I might be able to see if such interference were happening.



Also, kudos on getting your daughter to drive a 5-speed. Can I have her number?

I kid, I kid.

Ha ha! Both of my daughters (17 and 20 now) learned to drive with a 5-speed in my Miata, and both have stick shift cars. This daughter had a 5-speed in a Subaru Legacy GT before the Audi, and my younger daughter has a Protege5 with a 5-speed. They both insisted. They also both hate driving my wife's Honda Pilot (auto, of course).

Driving a stick-shift car is a dying art. I'm doing what I can to keep it alive. I've taught a bunch of folks to drive a stick.

Now back to the noise diagnosis.

I will try and get a video going. But the problem is getting the audio to come through with a phone-sourced video.

walky_talky20
12-02-2013, 04:00 PM
20, you say? Okay, okay. Back to work.

My vote is a bad inner CV joint. I actually had a bad rear inner CV joint and it made this repetitive clanking noise that would very often only happen during decel. Turning didn't effect because it's an inner joint (and mine was in the rear, but yeah). The boot was actually fine, but it was dry and loose inside.

The only thing was that it did get faster with speed. It clanked approximately once per revolution. Actually it would make the most sense if it clanked exactly once per revolution, but I didn't go all scientific on it.

Kronic Budz
12-02-2013, 11:40 PM
I have a 97 a4 2.8 5 speed and get the same sound you are describing with deceleration when in gear (engine braking). Easiest way to reproduce the sound is to drive the car cold, and get the car up to 3500 rpm's in say 3rd gear, and then just let off the gas and wait for the pinging/clacking to happen [:/]

Had this noise with my old 2.8 engine, and have it again with new swapped 2.8 w/ 105k miles. [headbang]

I notice this sound more when the engine is cold, and definitely more with windows down. I'd say from 2200-4k rpm's. It will make the clacking sound at no rhythm and sounds to me like exhaust leak and/or unburnt fuel igniting or something...

I am getting loss of power when the car is cold thinking the two problems might be correlated considering the "clacking" doesn't happen often when the engine is warmed up.

I am also getting the drivetrain "bang" like mentioned above when letting out the clutch too fast and mostly up shifting or pushing in clutch when coming to stop. I think it might be a combination of bad mounts, transmission/differential wear. I have new snub,motor, trans mounts and am thinking the "shock" is just getting amplified the the weakest link now being power ring, rear diff bushings and maybe carrier bushing. I'll start with power ring/rear diff and hopefully cleans it up enough.

RENOxDECEPTION
12-02-2013, 11:52 PM
I think I have this same problem with brand new axles. For me it only does it when it's cold out, and only does it when I'm leaving my block. It sounds like metallic pinging from my left front wheel.

I'll wait for a video to compare though.

mr72
12-03-2013, 06:24 AM
OK, here's the video:
https://dl.dropboxusercontent.com/u/9834677/20131203_073902.mp4

You can hear the clunk on upshifts, and then the "rapping" noise on decel at about 35 seconds and 42 seconds. Came out pretty good. I had both front windows down part way to hear this.

Now that I am forced to drive this car to work today, I notice that the engine has a grindy rasp that I really don't like. Sounds like it's being thrashed just driving routinely.

Artiemas
12-03-2013, 11:31 AM
The Clunk is the infamous B5 rear diff mount. It's been covered extensivly.

1.) From the factory its quite soft to begin with.
2.) Y'know..After some miles, it starts to wear and suddenly all it's really doing is just keeping the rear diff up on the underside of the car, rather than absorbing any shock loads.

Can it be fixed? Yeah, google around. There's some stuff you can do. A cheap, and pretty easy mod to do to it is fill it up with polyurethane.

mr72
12-03-2013, 12:01 PM
The Clunk is the infamous B5 rear diff mount. It's been covered extensivly.

That is what I guessed. Any idea about the other noise?

Kronic Budz
12-03-2013, 12:45 PM
That is what I guessed. Any idea about the other noise?

Do you notice the sound is present more when the engine is cold?

mr72
12-03-2013, 01:42 PM
Do you notice the sound is present more when the engine is cold?

No, it seems to be the same regardless of engine temps.

walky_talky20
12-03-2013, 02:26 PM
To me that sounds like popping from the exhaust. Is there a leak?

It almost sounds like there is some raw fuel going down the exhaust and igniting in the manifold. Perhaps a leaky injector. They should all be closed during decel, but if one is leaking you may get a pop like that.

mr72
12-03-2013, 02:45 PM
It sounds exhaust-like to me too. But the fact that it doesn't relate at all to engine rpm is puzzling. And my Miata does this popping due to injectors not closing through the exhaust and it's a very different sound, much more of a random crackle coming from the outlet of the exhaust (in the Miata, it's real, real loud... rest your foot on the pedal during decel and it crackles like a 240Z). This is coming from the front of the car, clearly, sounds like the front right side. Not from the exhaust outlet, which is where you'd expect an overrun crackle to come from.

Kronic Budz
12-03-2013, 03:09 PM
I'll get a video tonight leaving work of how mine sounds and try and distinguish at what rpm's in likes to happen at. Left or right side, ect and we can try and narrow done on what were both dealing with...

mr72
12-03-2013, 05:52 PM
I am not sure we are both dealing with the same thing, you said yours changes with engine rpm, right? Mine is sort of intermittent/random regardless of engine speed.

Also I discovered that if I put just a touch of pressure on the gas pedal while decelerating, not enough to change the engine braking, but just touch it, the noise goes away. So that seems to rule out something big moving/mechanical like an engine mount.

Kronic Budz
12-03-2013, 07:37 PM
I am not sure we are both dealing with the same thing, you said yours changes with engine rpm, right? Mine is sort of intermittent/random regardless of engine speed.

Also I discovered that if I put just a touch of pressure on the gas pedal while decelerating, not enough to change the engine braking, but just touch it, the noise goes away. So that seems to rule out something big moving/mechanical like an engine mount.


Mine is the same, just a touch of throttle input and the sound will go away. Only when off the gas completely. Mine isn't generally at the same rpm when it happens, but definitely in the range of 2500-4500 rpm's, anything higher then that can't be heard because of engine noise/intake noise. I'll post a video later ;)

Kronic Budz
12-03-2013, 11:06 PM
Video just can't come out with the road noise from my tires, and the loudness of my exhaust.

The "popcorn" sound is how I can best describe it is much more noticeable before engine is warm and hardly detectable when the engine is at full temp. It is around 300-3500 rpm's when there is enough "strain" on the engine.

The sound is coming from driver and passenger side evenly.

Does this sound like possibly a fuel issue?

mr72
12-04-2013, 07:30 AM
The sound is coming from driver and passenger side evenly.

Does this sound like possibly a fuel issue?

OK, that sounds like it could be the same thing. My daughter's car is not loud at all, so it's readily audible. I don't really rev it above 4500 rpm anyway.

I am going to have to have this car torn all apart this weekend so maybe I'll get a good look at what it could be. What genius put the thermostat behind the timing belt? And then what other genius designed a car that requires you to disassemble the entire front end of the car in order to do routine maintenance?

walky_talky20
12-04-2013, 08:29 AM
I'ts more genius if you could see how they put the front ends on these cars on the Audi assembly line. They have these little jigs at the perfect height that hold the bolts just right and line everything up. Takes like 30 seconds to bolt the entire front end on. Pretty neat.

mr72
12-04-2013, 09:08 AM
I'ts more genius if you could see how they put the front ends on these cars on the Audi assembly line. They have these little jigs at the perfect height that hold the bolts just right and line everything up. Takes like 30 seconds to bolt the entire front end on. Pretty neat.

Yeah, this is "neat", but it is basically the same exact complaint I have with all four or five German cars I have owned beginning with a '78 BMW and ending (well, not likely) with this current Audi: They make cars that are excellent the day they roll off the assembly line, and are a nightmare once the very first thing starts to wear out. Seems they just can't contemplate someone owning a car long enough to have to do a repair on it.

Just don't get me started on the bone-headed design "logic" on this Audi. I think I could pull the engine and put it back in my Miata more quickly than I will be able to change thermostat in this Audi. And you know I can adjust the clutch free play and pedal travel in my Miata and our Protege5 in about 5 minutes using a couple of end wrenches, and on this Audi it takes ... wait a minute... you mean you CAN'T ADJUST THE CLUTCH!?!! Just get used to driving it with the clutch engagement about 14" off of the floor. Best if you were born with a left leg that's 6" shorter than your right.

Sorry, it's awfully early for me to get this depressed. Happy thoughts! Last night I changed the lower control arm in my Miata in less than an hour. Ahh, serenity now! and it's going to take about 90 seconds to swap the shock on that side. Bless you, Mazda engineers. Just think about these happy thoughts, not that horrific black AWD German maintenance disaster area.

Lornnn
12-04-2013, 09:55 AM
Yeah... but... it's still a Mazda?

Google Image search Mazda Miata.

Then Google Audi A4.

'sayin.

mr72
12-04-2013, 10:33 AM
Yeah... but... it's still a Mazda?

Google Image search Mazda Miata.

Then Google Audi A4.

'sayin.

I own two Mazdas, and I adore my Miata. Suffice to say the Mazdas are just in a whole different league than the Audi and we'll leave it at that.

mr72
12-04-2013, 12:11 PM
Getting back on-topic ... sorry for the non-Audi-phile rant. Any ideas on what the cause of the non-clunk noise in my video could be? I will have the car apart on Saturday and it may be convenient for me to check some things while the front end is off. I just need to know what to check.

Kronic Budz
12-06-2013, 12:17 AM
Audi's aren't very hard to work on, when you have the knowledge and experience working on them, and have the right tools. They drive better or just as good then anything on the road. And look gorgeous, I would know. I've owned one for 6 years and have been a valet for 4 years haha.

Forget about the noise for now, inspect your exhaust for leaks and make sure other maintenance is up to date.

I'd start with checking/replacing mounts such as motor, trans, snub, REAR DIFF BUSHINGS, POWER RING and get the annoying clunk gone.