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Hello everyone, I am hoping this will be a very informative and helpful post to everyone in the D3 platform. My story starts with a noise that developed a few months back link here:
. Once I had verified the sound it dependent on RPM, I finally went into the engine compartment and found the noise is originating from the Hydraulic Adjusters. I know it may seem far-fetched but I verified it myself as well as my father using a stethoscope. To be more specific of how the sound occurs: (1) it occurs always when in gear and alway when accelerating up to a through 1,000 rpm. (2) While in park the noise only occurs whenever the rpm is raised to 1,300, then dropped and quickly spiked, nothing forceful but just a quick rpm rise once the rpm starts to drop from 1,300. To narrow down the search even further I used VCDS and the graphing function to graph bank 1 and bank 2 cam adjustment vs. RPM, and the results were quite amazing. I found that the noise was directly related to (2) as stated above. Here is the image of the graph:
Notice the spike in cam adjustment (advancing the intake cam) as the rpm is spiked (in park).
This second graph is related to a very low acceleration less than 1500rpm (around 0/-1 degrees of intake cam advancement) a stop, then acceleration which results in a advance and retard (spike) to cam adjustment then a very low acceleration less than 1500 rpm up to and greater than 1500 rpm which results in an advancement of cam adjustment (around 21 degrees of intake cam advancement).
So to put it simply I have found the noise I am concerned with to be related to the hydraulic adjusters to be advancing the intake timing and quickly retarding it when accelerating though 1000rpm and/or though 1,300rpm in park then applying a slight spike in rpm. If my knowledge of the hydraulic adjusters are correct they are operated by a solenoid which gets a signal from the ECM to advance timing. If everything listed above is taken into account plus the data I have collected with VCDS it appears that the hydraulic adjusters are getting a bad signal from the ECM or something in the wiring has gone wrong. To be honest I am not sure, but one thing I am sure of with the symptoms I have and with the data I have collected it does not appear to be a mechanic problem. To be even more detailed I had a friend ride with me while I drove though certain speeds to collect data on the Bank 1 and Bank 2 adjustment angle and found it to be:
0 MPH: Bank 1 (degrees): -1/0 Bank 2 (degrees): -1/0
20 MPH: Bank 1: 21 Bank 2: 21
40 MPH: Bank 1 : 21 Bank 2: 21
60 MPH: Bank 1: 21 Bank 2: 21
80 MPH: Bank 2: 21/22 Bank 2: 21/22
Any and all opinions would be helpful. Plus any clarification that is needed please let me know as I am writing this at close to 2AM.
Unplug the electrical connectors for the timing adjuster solenoids and see if the noise is still present. Then plug one back in at a time and see if the noise returns with one or the other.
Although I think at least one of your timing adjusters is faulty as they shouldn't make that noise when actuating. If the ECU is sending signals and VCDS is logging it appropriately and there are no error codes then there are no problems with the ECU. It's working normally.
It's also worth noting that the valve timing adjustment parameters are dynamic and based off numerous inputs. They are not simply rpm dependent so the valve timing will be adjusted both up and down at different RPMs depending on conditions at the time.
Unplug the electrical connectors for the timing adjuster solenoids and see if the noise is still present. Then plug one back in at a time and see if the noise returns with one or the other.
Although I think at least one of your timing adjusters is faulty as they shouldn't make that noise when actuating. If the ECU is sending signals and VCDS is logging it appropriately and there are no error codes then there are no problems with the ECU. It's working normally.
It's also worth noting that the valve timing adjustment parameters are dynamic and based off numerous inputs. They are not simply rpm dependent so the valve timing will be adjusted both up and down at different RPMs depending on conditions at the time.
What makes you think one is faulty? Does anyone else have any data the Bank 1 and Bank 2 adjustment angle?
Because there's nothing else in there able to cause a differing noise in line with the valve timing changing.
You've been analyzing this to death for months now and second guessing every suggestion made. It's time to either dive in yourself and start taking things apart or take it to someone who can do it for you.
In other words, it's time to **** or get off the pot.
Standard automotive troubleshooting techniques work great for this. Use a mechanic's stethoscope to find general area of the noise and then replace all valve lifters in that area. Or, buy the cheaper ones from ECS and replace every one in the engine.
I doubt it's the hydraulic valve lifters. If it were it would make the same noise all the time, regardless of valve timing. The relationship between cam lobe and hydraulic valve lifter is not changed in any way by the valve timing adjusting.
You've found that the noise changes at exactly the same time the valve timing changes. Unplug the suspect timing actuator and then see if the noise change no longer occurs when the timing signal is sent by the ECU. If not, then it's obviously that timing actuator at fault and further investigation/replacement is needed.
I doubt it's the hydraulic valve lifters. If it were it would make the same noise all the time, regardless of valve timing. The relationship between cam lobe and hydraulic valve lifter is not changed in any way by the valve timing adjusting.
You've found that the noise changes at exactly the same time the valve timing changes. Unplug the suspect timing actuator and then see if the noise change no longer occurs when the timing signal is sent by the ECU. If not, then it's obviously that timing actuator at fault and further investigation/replacement is needed.
FWIW, my son's A6 4.2 has the same noise as jlbell is describing, at those RPM's, and I did unplug the cam adjuster solenoids one at a time, and the noise was gone, the drivers side bank was the loudest, the passenger not so much at first, only problem with leaving them unplugged was that there is a great loss of power due to being in retarded mode for cams, SO after much searching, reading, asking questions of people in this field, it cam to replacing both cam tensioners costing me $1300.00 for both from the dealer, while my son and a friend were doing the tear down they discovered that the drivers side unit was missing the screen, so after that big job, GUESS WHAT, the noise was gone for about two weeks on his DD, but then returned, albeit not as loud ( we keep telling ourselves that so I can justify the $1300.00 just for the 2 pieces, plus more $$$ for other items...) now the are both equal in sound, THEN I found a PM from jlbell and he sent me the PDF on the oil retention valves located under the intake, BUT the A6 4.2 does not have those, bummer, SO my son has now found the intake noise that it developed when I first purchased the vehicle has returned, the cams are much quieter, but the noise is at the advancing of the cams, but it turns out that the intake action (3 stage intake) and advancement of the cams is at the same rpm range, so when he now unplugs the solenoid for the intake vacuum pods the noise is gone, besides the very light chain noise from cam tensioners.
So now he is looking far a complete intake, as his does not seal properly and rattles through the stages.
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So jlbell,
Unplug your vacuum pods and see what happens.
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Last edited by JohnnyJ A6Q; 01-20-2016 at 05:38 PM.
01-13-2016, 10:39 PM
Hydraulic Adjusters
