A Class - Engine Knock - Help Please

[b_b]

Hi all,

A rhythmic knocking noise has developed with my 2010 A160 (W169) Diesel BlueEfficiency - I know these can be difficult to diagnose but I'm hoping someone might have some insight please!

It's a dull regular rhythmic sound, not a high pitched metal-on-metal, deeper than that. It's almost like a drumbeat over and above the usual sound of the engine.

It is linked to the engine RPM - higher RPMs increase the speed of the noise, even when not moving
It is not linked to the car speed - it still happens when driving down a main road at a good speed (but is obviously harder to hear because, I assume, of the normal noise of the road)
It is not linked to engine temperature - it happens when the car's just been started from cold, just the same as after a drive when the engine is at 80 degrees C.
It is not linked to leaking oil - there's no obvious oil leak present

I hope that's enough information to maybe pinpoint some things, but any thoughts would be greatly appreciated!

 

[Northernsands]

Not a clue, but it might be useful to know if it's happening once per revolution (crank?), or every other revolution (injector?). Does the clutch position make any difference (for a manual)? I don't know if those engines suffer from the 'Black Death', but a worn injector seal might make a chuff noise that might sound different through the engine covers.

 

[Bay Leaf]

If you're handy enough and got the tools I would remove the auxiliary (used to be known as the fan belt) and see if the noise stops. If it does it's something that belt drives or goes round e.g. alternator/ water pump/ air con compressor/ belt idler pully.
Worth a try.

 

[peterws1957]

If you're handy enough and got the tools I would remove the auxiliary (used to be known as the fan belt) and see if the noise stops. If it does it's something that belt drives or goes round e.g. alternator/ water pump/ air con compressor/ belt idler pully.
Worth a try.

Had this problem on one of mine recently. Sounded like a clattering in the engine, even close up. I did gulp a bit but it turned out to be the crankshaft pulley which wasn't wobbling and looked to be ok but on removal found to be slightly coming apart and contacting the water pump housing. I was a touch relieved.