1.4 AUA / BBY Tap Tick Rattle Knock

A

a-zwo

Member
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 :)
 
I have three 1.4 petrols and have been riding in some more, and all these cars have a typical load dependant tic. No load=no sound. Apply some tiny load=ticking sound starts.
My opinion is that the problem is piston slap but I havent taken any of the engines apart to verify.
Similar to your text the sound is reduced as the engine gets warm, but does not totally disappear.
 
a-zwo said:
Overheat
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?
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My A2 is a TDi but I have experienced tap tap noises with other petrol engines.
A classic Mini over heated and cooked its valves. It made a tap tap noise as combustion gasses escaped past the valves on the power stroke. There was a loss in performance and economy.
Two VAG 1.8 engines blew out their exhaust manifold to head gaskets. A tap tap noise was heard as gasses left the engine, no loss of performance.
All three engines sounded like they had tappet problems.
 
lavandism said:
Piston slap can be dealt with rather effectively by opting for a thicker oil. I switched to 5w40 from 5w30 and the engine is the quietest it has ever been in 1,5 years of ownership.

Edit: 1.4 petrol (AUA)
Click to expand...
In your case, do you only have a sound at idle and under load, or is the sound there at all times?

So with what Joga and LittleDog have said, it would probably be useful to have a tapping engine and take it apart to see if it is indeed piston slap or something else.
 
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a-zwo said:
In your case, do you only have a sound at idle and under load, or is the sound there at all times?

So with what Joga and LittleDog have said, it would probably be useful to have a tapping engine and take it apart to see if it is indeed piston slap or something else.

To check piston slap, I suppose the best option is to take the head off and just try rocking the pistons. If the head gasket isn’t blown, there should be no requirement for a skim?
Click to expand...
Always, used to be more notable at higher revs with 5w30. With 5w40 no tapping, though I did not have a chance to test the car properly yet.
 
lavandism said:
Always, used to be more notable at higher revs with 5w30. With 5w40 no tapping, though I did not have a chance to test the car properly yet.
Click to expand...
Can't see oil viscosity affecting piston slap, more likely hydraulic tappets imo.
The FSI does it on startup, but only for a few seconds, then it's gone. Always assumed it was oil drain back from the tappets. Should be a non return valve in there ...
Mac.
 
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