300TDi knock noise

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Originally Posted by rick130

Other than the oil pressure collapsing at idle, I found big end noise only really noticeable on the overrun at high revs in aTdi?

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I plastigauged the bottom end 1000km ago.
I'm basically out of ideas at this point.
I have seen videos of other 300TDis that make the same noise.
I'm leaning towards it just being a sharp loud combustion knock. No idea why though...

Maybe stitch it back together
Drop the timing back to 1.5mm of lift
You’ll lose a little bite but if the noise changes at least you’ll know it is just knock ?

I’m super frustrated for you mate
I too would be chasing that noise down!

S

Quote:

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Originally Posted by rick130

Other than the oil pressure collapsing at idle, I found big end noise only really noticeable on the overrun at high revs in aTdi?

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I guess that depends. A knocking big end is very serious in ANY engine AFAIK. The more it knocks the worse it gets. Once the bearing loses the oil wedge then it's only a matter of time, unless 300 TDis have some sort of secret armour.

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Originally Posted by johntins

I guess that depends. A knocking big end is very serious in ANY engine AFAIK. The more it knocks the worse it gets. Once the bearing loses the oil wedge then it's only a matter of time, unless 300 TDis have some sort of secret armour.

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So a big end can knock and the engine can still have good oil pressure?

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Originally Posted by roverrescue

Sounds to me a bit vacuum pump - the world won’t end if you pop the pump off, jam a bit of cardboard against the holes and run at idle

If no change is check your tappets- not quite right pitch for tappet strike buts it’s quick and easy to cross off

Then I would Check the IP lift at TDC (timing)
A 300tdi with too much advance gets a sharp knock like that at idle

I would be surprised if those three don’t pull it up

S

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*Yep, sounds like the vacuum pump to me, but its not bad.

answer to other replies:
*Trouble is you can replace the vacuum pump and the new one can have the same sound.
*Yes it will still have vacuum.
*Overall sounds pretty ok for a 300tdi

Quote:

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Originally Posted by roverrescue

Maybe stitch it back together
Drop the timing back to 1.5mm of lift
You’ll lose a little bite but if the noise changes at least you’ll know it is just knock ?

I’m super frustrated for you mate
I too would be chasing that noise down!

S

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Good tip. I retarded the IP as far as it would go on the pulley and the engine ran like crap but the knock was still there. So i guess it's not knock due to the IP timing...
All the injectors are new too.
I guess it could be rod knock/tap but i'm 100% certain all nuts were done up to torque and then double checked! So, if it was rod knock something strange must have happened...

Quote:

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Originally Posted by johntins

I guess that depends. A knocking big end is very serious in ANY engine AFAIK. The more it knocks the worse it gets. Once the bearing loses the oil wedge then it's only a matter of time, unless 300 TDis have some sort of secret armour.

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John, I'm not saying a big end knock is not a problem, its a huge problem, I'm just saying IME it's not that noticeable, at least initially, in a Tdi.

Ever since i replaced head on mine had pretty much same sound. That was few years ago and few k kms. Engine still runs well.

I assume it was since i changed head. Might have been there even before but don’t remember noticing. Was actually someone here that picked it up on a video i posted it which alerted me to it.

When i was doing tappets one of rods wasn’t seated properly and it went with a loud pop as i turned engine. Had me paranoid that I’d done damage to follower. Another issue i have is on start up the idle always seems to struggle like a valve is stuck or something. Happens for a few seconds.

I learned to live with it. One theory i had was possible issue with the amc heads. Other theory (more plausible) is i did something wrong. But as mentioned, runs well and never given me problems. Touch wood.

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Originally Posted by Fausto79

Ever since i replaced head on mine had pretty much same sound. That was few years ago and few k kms. Engine still runs well.

I assume it was since i changed head. Might have been there even before but don’t remember noticing. Was actually someone here that picked it up on a video i posted it which alerted me to it.

When i was doing tappets one of rods wasn’t seated properly and it went with a loud pop as i turned engine. Had me paranoid that I’d done damage to follower. Another issue i have is on start up the idle always seems to struggle like a valve is stuck or something. Happens for a few seconds.

I learned to live with it. One theory i had was possible issue with the amc heads. Other theory (more plausible) is i did something wrong. But as mentioned, runs well and never given me problems. Touch wood.

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Interesting... I've been trying to think how a damaged follower could make that clack/knock noise though? After all, if the the valve clearances are still good after running the engine wouldn't that mean that the follower assembly has no excessive play in it?

Another question:
Can you mix and match camshafts and lifter assemblies? i.e. can i put brand new or different (used) lifter assemblies on an old camshaft or a new camshaft in an engine and use old lifters?