Weird Intermittent Rattle at idle (2ZZ)

Alex Knight · September 11, 2025, 12:03

Hi all,

My 2ZZ has developed a strange intermittent rattle at idle.

I've replaced the aux belt tensioner with a new OEM unit.

I'm thinking that it might be alternator pulley bearing.

I'm 99.9% it's not engine internals related due to its intermittent nature.

Any ideas what it might be?

Carolyn · September 11, 2025, 13:43

Get a stethoscope and hunt around. Take the cannister out while you do it.

Alex Knight · September 16, 2025, 20:50

@Carolyn

Possibly timing chain tensioner?

Or timing chain itself?

Either way, booked in a week on Friday as I don't have the time at the moment.

Carolyn · September 17, 2025, 09:08

Quote from: Alex Knight on September 16, 2025, 20:50@Carolyn

Possibly timing chain tensioner?

Or timing chain itself?

Either way, booked in a week on Friday as I don't have the time at the moment.

Tensioners do wear out and start to leak oil past the little piston. More likely the tensioner than the chain. The intermittent nature of it suggests the tensioner more than the chain.