A8 D3 oil retention valves theory
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AudiWorld Junior Member
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A8 D3 oil retention valves theory
My A8 D3 of 2003 with the 3.7L V8 has the dreaded chain rattle on cold startup. The noise has become worse over a few weeks. I've been out of the country for a while so the car sat for 2+ weeks. From my research it's either the chain guides/tensioners that are broken, or it's the oil retention valves allowing oil to leak out and thus leaving the tensioners without tension untill oil pressure built up.
Sound clip of the horrible rattle:
https://youtu.be/DSlblqZLrq8?si=jjw2hnRM4AIxWb3G
So after some more research I tried to build up oil pressure by disabling ignition. When starting the car after first building up oil pressure for 10 seconds, there is no rattle at all and the engine sounds just fine.
Is my conclusion correct when this makes me believe it is the oil retention valves? In theory if the rattle is gone with oil pressure and the rattle is always there when there's no pressure (because all oil leaked back), I feel like the tensioners and guides themselves are not the issues.
Curious to your thoughts. I'm down to take out the engine for the guides, but only if really needed. I'd much rather do the retention valves if my theory is correct.
Thanks
Sound clip of the horrible rattle:
https://youtu.be/DSlblqZLrq8?si=jjw2hnRM4AIxWb3G
So after some more research I tried to build up oil pressure by disabling ignition. When starting the car after first building up oil pressure for 10 seconds, there is no rattle at all and the engine sounds just fine.
Is my conclusion correct when this makes me believe it is the oil retention valves? In theory if the rattle is gone with oil pressure and the rattle is always there when there's no pressure (because all oil leaked back), I feel like the tensioners and guides themselves are not the issues.
Curious to your thoughts. I'm down to take out the engine for the guides, but only if really needed. I'd much rather do the retention valves if my theory is correct.
Thanks
AudiWorld Member
Joined: Sep 2018
Posts: 394
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See https://www.audiworld.com/forums/a8-...3-kit-3024809/
At startup there is some rattle in these cars, especially after they sit for a while. Starting oil pressure is a factor for sure.
There are 2 schools of thought:
At startup there is some rattle in these cars, especially after they sit for a while. Starting oil pressure is a factor for sure.
There are 2 schools of thought:
- The noise bothers me and is loud enough to cause me to do repairs (and I have the funds to do it)
- Oil check valves
- Cam tensioners (anecdotally last till around 220k km)
- I have a noise but will wait for the car to throw codes before taking action
- Trust the car to tell you when it needs to be fixed
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Joined: Oct 2001
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From: SF Bay Area, CA
Having done check valves, those of course are way easier than full motor pull You basically need to take off intake and get to the valley (between the "V"pan cover and remove. Get a new gasket for that in advance of course too, From decade + old memory of my C5 4.2, a good time to do the coolant temp sender too--which is pretty low down in back and way easier to deal with if intake iis removed.
Thread Starter
AudiWorld Junior Member
Joined: Dec 2024
Posts: 19
Likes: 2
See https://www.audiworld.com/forums/a8-...3-kit-3024809/
At startup there is some rattle in these cars, especially after they sit for a while. Starting oil pressure is a factor for sure.
There are 2 schools of thought:
At startup there is some rattle in these cars, especially after they sit for a while. Starting oil pressure is a factor for sure.
There are 2 schools of thought:
- The noise bothers me and is loud enough to cause me to do repairs (and I have the funds to do it)
- Oil check valves
- Cam tensioners (anecdotally last till around 220k km)
- I have a noise but will wait for the car to throw codes before taking action
- Trust the car to tell you when it needs to be fixed
As for those 2 points: the noise on startup is definitely horrible, did you see the youtube video I added in my first post? I feel like if I don't do something, it will grenade itself eventually. The car has 199k km so 123k miles and has always been taken good care of.
Having done check valves, those of course are way easier than full motor pull You basically need to take off intake and get to the valley (between the "V"pan cover and remove. Get a new gasket for that in advance of course too, From decade + old memory of my C5 4.2, a good time to do the coolant temp sender too--which is pretty low down in back and way easier to deal with if intake iis removed.
AudiWorld Member
Joined: Sep 2018
Posts: 394
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In your other thread about this problem I linked my thread regarding cam tensioner replacements. At the end of that thread I did detail the replacement the check valves on the 4.2 with pictures. Should be the same for you.
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Joined: Oct 2001
Posts: 15,311
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From: SF Bay Area, CA
The gasket for the valley pan cover is very one off, even when I bought it over a decade ago. It was dealer only back then and hard to get locally when I needed it. Don't recall on check valves, but for most non- Audi deep dive enthusiasts, it is a little known or even understood part. Coolant temp sensor and intake gasket set (Reinz etc.) easy to find.
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Like a reserve of oil sitting at the top of the engine for the tensioners and lifters to draw from..? So the valves open when there's oil pressure (so oil can circulate) engine) and close when the pressure is absent (and some oil is retained up there) for the next engine start/stop cycle...
Last edited by 91quattro; Jan 22, 2025 at 02:05 PM.
Thread Starter
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Other reply seems to have specific links/how to's. I was going to just point to old shop manual that you would need to get--these days probably digital download.
The gasket for the valley pan cover is very one off, even when I bought it over a decade ago. It was dealer only back then and hard to get locally when I needed it. Don't recall on check valves, but for most non- Audi deep dive enthusiasts, it is a little known or even understood part. Coolant temp sensor and intake gasket set (Reinz etc.) easy to find.
The gasket for the valley pan cover is very one off, even when I bought it over a decade ago. It was dealer only back then and hard to get locally when I needed it. Don't recall on check valves, but for most non- Audi deep dive enthusiasts, it is a little known or even understood part. Coolant temp sensor and intake gasket set (Reinz etc.) easy to find.
Like a reserve of oil sitting at the top of the engine for the tensioners and lifters to draw from..? So the valves open when there's oil pressure (so oil can circulate) engine) and close when the pressure is absent (and some oil is retained up there) for the next engine start/stop cycle...
---
Quick update: I plugged in a fused on/off switch in the fuse #30 (30A fuse for ignitioncoils) on the passenger side which controls ignition. While I wait on the parts, I've noticed that whenever I turn off ignition in the morning and crank the car for ~10 seconds to build up oil pressure, the rattle is completely gone if I then start the car. This at least allows me to not break the car while waiting on parts. Maybe this will help someone who finds this topic in the future :-)
