I started my car up today for the first time in a while and it was making this really loud tapping noise.

 

tap tap tap tap etc.

 

What could this be and how much of a big job is it?

Take it for a good run and it will quieten down, its just cos its been sat a while.

Oh right, good good. Better get some Tax :x:

I had the same with mine, aint been run for a few weeks and it does tap. once it warms up the tapping should quieten right down and hopefully stop, if it doesnt stop after a while then it could be your tappets

Hydraulic tappets, the same happened to mine when I left it standing, not happened since I have been using it.

quite common,most 300s do this for a few secs after startup until oil gets round the lifters,if it doesnt settle do an oil change with some good quality synthetic,and drive the car more regulary

:) mine done this when i put it back on the road after it was sorn for 13mths done full oil and filter change hav`nt heard it tap at all since :)

There is a very small valve in the block that is supposed to hold the oil in the hydralic valve lifters, when this gets gunged up then it will tap tap tap when cold. About £5 for each valve (2, 1 for each head) and loads of labour to change.

There is a very small valve in the block that is supposed to hold the oil in the hydralic valve lifters, when this gets gunged up then it will tap tap tap when cold. About £5 for each valve (2, 1 for each head) and loads of labour to change.

 

 

Shouldn't be lots of labour if it is the VVT springs you are talking about?

Didn't mention the VVT at all if you read the thread, as that is not the problem I was talking about.

Ouch sorry bud, can you tell me which valve it is :)

actually it has nothing to do with any valve...as far as I know there isn't a valve in the block or head, only 2 (small) oil jets in the oilpassages to the head, but these are there to regulate the oilflow/pressure to the heads and if they get blocked for some reason you'll have far more serious problems.

 

There is a small checkvalve inside each lifter, to keep the oil inside the lifter, but this valve normally isn't the problem either.

 

The actual problem is caused by a problem in the design of the lifters themselves: inside the lifters is a small round plate between the lifterbody and the housing (left in the picture)

This plate has a small groove that is fed with oil through 2 VERY tiny pinhead holes on the far ends of the groove to create a thin layer of oil between the inside top of the lifter and the plate to prevent the ticking sound:

 

 

The problem is, it's very easy for one or both of these tiny holes to get blocked and the result is that the groove will no longer fill up with enough oil and this will cause the ticking sound.

In the worst case, the groove wears out because of the lack of oil and this causes the lifter to tick allways.

 

-Eric

In the oil feed to each head is a check valve, its there to prevent drainback of the lifters, when the oil hasn't been changed in a while it gets stuck open and the oil drains out of the heads over time. You can replace all the lifters but if there is no oil staying in the heads then you will get the tapping sound on startup.

 

There is also a small orifice at the other end of the oil gallery, maybe it was this one you were thinking about.