Noisy 1.4 petrols has been mentioned a few times, and I don’t think there has really been a clear guide to diagnose and fixing the various issues that can cause this (at least not all in one place)
So I thought I could add what I know, and maybe some of the other experienced members of the forum could fill in the gaps.
Again this applies to 1.4 AUA and BBY engines.
Rod knock
Unheard of on these engines, but included for completeness
What
Rattling sound that increases in speed and volume with engine RPM. It will sound like it’s happening at the same speed as the engine, so 1000 RPM would be 1000 “knocks” per minute. Will happen regardless of engine load.
Cause
Failed big end bearing (generally due to oil starvation). The sound is the rod “rattling” on the crank.
Fix
Realistically, a new engine in the case of the A2 because they are so cheap and the crank would most likely be destroyed. (You’re not supposed to replace the crank on AUA/BBY, reference: Audi SSP)
Piston Slap
Quite common, anecdotally more so on BBY than AUA.
What
Rattle/whoosh/tap sound that is worse when cold and may totally go away when the engine is warm. Will increase in speed with engine RPM but not in volume. Will happen regardless of engine load (can someone confirm)
Cause
Piston skirt wear, which could be caused my improper oil. The piston becomes undersized for the bore and “rattles” when cold. As it expands it stops rattling
Fix
If the engine does not use oil, and the sound doesn’t bother you, this is no problem. A heavier grade of oil may help. To fix it permanently, new pistons are required.
Lifter tick
May be quite common
What
Higher pitched tap/tick/click sound from the top of the engine. Will increase in speed with engine RPM but not volume. The rate will be half the engine RPM. Will happen regardless of engine load.
Cause
These engines use hydraulic lifter that can wear/leak/collapse. This means that there is no oil cushion to dampen the sound of the cams moving the valves, which cause the noise
Fix
Generally no fix needed. Replacing the lifters may help, but the issue may come back. If you do this job, use INA lifters as they are original parts
Exhaust leak
Not an internal engine issue, but it may sound like one. Could make any sound at any RPM, but would be more noticeable when the engine is under load and not in overrun.
Overheat
This one I need some help with. If the engine has overheated from the past, it is possible the valves are not sealing properly as the head/valves has become distorted. This results in a sound which could be a tap/rattle as exhaust gas forces its way past the valve. Would happen at any engine RPM, but only under load. @Little Dog I think you have some experience of this?
I will add some more later, and obviously include any feedback in this post. Please feel free to correct any/all of it
So I thought I could add what I know, and maybe some of the other experienced members of the forum could fill in the gaps.
Again this applies to 1.4 AUA and BBY engines.
Rod knock
Unheard of on these engines, but included for completeness
What
Rattling sound that increases in speed and volume with engine RPM. It will sound like it’s happening at the same speed as the engine, so 1000 RPM would be 1000 “knocks” per minute. Will happen regardless of engine load.
Cause
Failed big end bearing (generally due to oil starvation). The sound is the rod “rattling” on the crank.
Fix
Realistically, a new engine in the case of the A2 because they are so cheap and the crank would most likely be destroyed. (You’re not supposed to replace the crank on AUA/BBY, reference: Audi SSP)
Piston Slap
Quite common, anecdotally more so on BBY than AUA.
What
Rattle/whoosh/tap sound that is worse when cold and may totally go away when the engine is warm. Will increase in speed with engine RPM but not in volume. Will happen regardless of engine load (can someone confirm)
Cause
Piston skirt wear, which could be caused my improper oil. The piston becomes undersized for the bore and “rattles” when cold. As it expands it stops rattling
Fix
If the engine does not use oil, and the sound doesn’t bother you, this is no problem. A heavier grade of oil may help. To fix it permanently, new pistons are required.
Lifter tick
May be quite common
What
Higher pitched tap/tick/click sound from the top of the engine. Will increase in speed with engine RPM but not volume. The rate will be half the engine RPM. Will happen regardless of engine load.
Cause
These engines use hydraulic lifter that can wear/leak/collapse. This means that there is no oil cushion to dampen the sound of the cams moving the valves, which cause the noise
Fix
Generally no fix needed. Replacing the lifters may help, but the issue may come back. If you do this job, use INA lifters as they are original parts
Exhaust leak
Not an internal engine issue, but it may sound like one. Could make any sound at any RPM, but would be more noticeable when the engine is under load and not in overrun.
Overheat
This one I need some help with. If the engine has overheated from the past, it is possible the valves are not sealing properly as the head/valves has become distorted. This results in a sound which could be a tap/rattle as exhaust gas forces its way past the valve. Would happen at any engine RPM, but only under load. @Little Dog I think you have some experience of this?
I will add some more later, and obviously include any feedback in this post. Please feel free to correct any/all of it