Audi 2004 S4 engine rattle from cold start up

[peaty]

Hi all.

Im new so bear with me here but couldn't find what I was looking for (maybe Im searching wrong).

I have a 2004 S4 V8 cabriolet with approx 70k on the clock and there is a bad rattle sound from engine on start up. Now I know this is common (apparently) on these engines but I just cant leave it any longer - its sounds terrible when it starts and my friends look at me when they hear it.

It dosn't matter how long the car is sat for but anything over an hour and it will do it. Now I have read that its the chains and the tensioners but then I read that people have changed all of those and they still do it!

Can anyone tell me what the exact cause is? I have flushed the motor and changed the oil and filter with 5W 40 Shell Helix and nothing changed.

Do these engine have varaitors and if so are these the cause? I know its due to oil pressure build up, but within which part exactly? Could it also be a lazy oil pump and are there any modification from audi's eg fitting of a one way oil valve anywhere into the head caps for example to help??

I have come across this link on youtube where someone has managed a fix with the engine in place. http://www.youtube.com/watch?v=AiTiJ5mnvQ4 Would this cure it? I'm aware the lump may have to come out, which is fine - I can tackle this, but this must be worth a shot surely before commiting to all those hours of work?

Any suggestions would be appreciated and also would anyone know approx costs or even part numbers of what I may need?

Thanks in advance and sorry if this has been covered a million times....

[a8 tech]

Hi all.

Im new so bear with me here but couldn't find what I was looking for (maybe Im searching wrong).

I have a 2004 S4 V8 cabriolet with approx 70k on the clock and there is a bad rattle sound from engine on start up. Now I know this is common (apparently) on these engines but I just cant leave it any longer - its sounds terrible when it starts and my friends look at me when they hear it.

It dosn't matter how long the car is sat for but anything over an hour and it will do it. Now I have read that its the chains and the tensioners but then I read that people have changed all of those and they still do it!

Can anyone tell me what the exact cause is? I have flushed the motor and changed the oil and filter with 5W 40 Shell Helix and nothing changed.

Do these engine have varaitors and if so are these the cause? I know its due to oil pressure build up, but within which part exactly? Could it also be a lazy oil pump and are there any modification from audi's eg fitting of a one way oil valve anywhere into the head caps for example to help??

I have come across this link on youtube where someone has managed a fix with the engine in place. http://www.youtube.com/watch?v=AiTiJ5mnvQ4 Would this cure it? I'm aware the lump may have to come out, which is fine - I can tackle this, but this must be worth a shot surely before commiting to all those hours of work?

Any suggestions would be appreciated and also would anyone know approx costs or even part numbers of what I may need?

Thanks in advance and sorry if this has been covered a million times....

Under the inlet manifold in the v there are oil pressure regulators that may stick but there is no easy answer without dismantling the engine
One quick test is to asses the oil pressure via measured value block 3 if I remember in address 17
Crank the engine and you should see if the pressure is ok or more accurate is the mechanical oil pressure test at cranking and residual oil pressure to understand if there is a pressure issue or wear of the chain sets or tensioners
The cam variaters may be noisy buy would associate this with more constant engine running
Try a basic setting of the cam tensioners and listen to them
Also check valve timing for possible streatched chains
You could scope the camshaft sensors if you find the pattern distorted it could indicate chain slackness


Sent from my iPhone using
My fat fingers

[peaty]

Under the inlet manifold in the v there are oil pressure regulators that may stick but there is no easy answer without dismantling the engine
One quick test is to asses the oil pressure via measured value block 3 if I remember in address 17
Crank the engine and you should see if the pressure is ok or more accurate is the mechanical oil pressure test at cranking and residual oil pressure to understand if there is a pressure issue or wear of the chain sets or tensioners
The cam variaters may be noisy buy would associate this with more constant engine running
Try a basic setting of the cam tensioners and listen to them
Also check valve timing for possible streatched chains
You could scope the camshaft sensors if you find the pattern distorted it could indicate chain slackness



Sent from my iPhone using
My fat fingers

Hi there, thanks for your response but I dont think the oil pressure is the main issue here. I am quite willing to strip out the motor but when you have got everything apart I bet everything will look okay with northing abnormal standing out. When I rip the motor out, I just want to be assured its fixed as Im happy putting chains & tensioners on there but would be gutted if it was the same after all that effort.

I do work at a main dealer although not audi and do not have access to aftermarket scanners so I cannot scope the camshaft sensors but Im guessing the EML would be on if it was that bad or the noise would continue for a longer peroid or even under certain circumstances. The manfactuers I work or have lots of variator issues on start up just like mine so thats why I asked. Has anyone changed these before for this reason?

Also did anyone look at the youtube link and if so, any thoughts??

[a8 tech]

Hi there, thanks for your response but I dont think the oil pressure is the main issue here. I am quite willing to strip out the motor but when you have got everything apart I bet everything will look okay with northing abnormal standing out. When I rip the motor out, I just want to be assured its fixed as Im happy putting chains & tensioners on there but would be gutted if it was the same after all that effort.

I do work at a main dealer although not audi and do not have access to aftermarket scanners so I cannot scope the camshaft sensors but Im guessing the EML would be on if it was that bad or the noise would continue for a longer peroid or even under certain circumstances. The manfactuers I work or have lots of variator issues on start up just like mine so thats why I asked. Has anyone changed these before for this reason?

Also did anyone look at the youtube link and if so, any thoughts??

If you are sure there is no pressure issue then you will need to identify the noise via chassis ears or similar


As for the chains then scoping will show a fluctuation at the hall senders of the cams and unless the senders are short to earth or open circuit it will not show a fault as the senders are reading pre set points
You will need to capture a trigger of the pattern and look for irratic frequency indicating stretch
The varieties will compensate for chain wear as will the tensioners to keep the valve timing within the window
As you say it's after a standing time then I would confirm oil residual pressure as it seems the pressure is dropping off


Sent from my iPhone using
My fat fingers