Had same problem years ago in my Audi A4. took car to stealers They replaced chain tensioner & run fine after.

 

Exhaust leak? you seem to have done everything else, did the sound come immediately after the injectors were re-furbed? have you done a leak off test just to check the injectors really are good.

+1 of the chain tensioner, didn't think of that

 

Thanks for your replies. Yes the tapping started after injectors had been worked on. No, not checked exhaust yet and not done a leak off test. I was going to just buy a known good injector and fit it to each cylinder in turn to see if it has any effect. As for chain tensioner that's a possibility but wouldn't you expect the tapping to be nearer the front of the engine not around number 4 ?

fezzalad

 

Thanks for your replies. Yes the tapping started after injectors had been worked on. No, not checked exhaust yet and not done a leak off test. I was going to just buy a known good injector and fit it to each cylinder in turn to see if it has any effect. As for chain tensioner that's a possibility but wouldn't you expect the tapping to be nearer the front of the engine not around number 4 ?

Again taps are so deceptive and it doesn't follow that they come from the location because of the way sound transmits through the block.

Get a leak off test done first, also how loud is the noise with the filler cap off, you should get one load tick which is the vacuum pump but anymore might give you a clue to valves or not

 

With filler cap off I do get the loud tick from the vacume pump so no more clues here. Just had a look what's involved with checking the timing chain tensioner and it looks like a pretty major job, head off, sump off, so will need to be pretty sure or at least out of all other easier options first.

 

You are lucky on the M57, is has it is own covers and so can be accesses without taking the head off or removing the engine. Feel sorry for the new N57 owners, they put the chain at the back and so it is a engine, head and sump off job to change

 

If you can get hold of a stethescope you might be able to pin down the source closer, sound locations are tricky, sound can seem to come from a one area but +1 with what Matt said about how sound travels. Its deceptive.

I'd also guess a worn tensioner, making the chain louder, but can understand why you'd want to eliminate every other possibility first. The fact she's driving fine and pulling fine with no other apparent symptoms is a good thing, and kind of supports the tensioner theory.

 

Thanks cendrian, I don't have a stethoscope but using the old fashioned method of a metal rod against my ear,I've been all over the top of the engine and the tap is very apparent when the rod is pressed against the bodies of number 3 and number 4 injectors. This coupled with the noise starting after injectors had been worked on makes me feel a good starting point is eliminating the injectors, which is why number 4 was moved to 1. I think I'll try moving 3 to 6 as the only cost is my time and ultimately I'm trying to avoid spending a grand finding a 200 quid fault.

I have just noticed there is a just noticeable metallic 'clack' a split second after the starter engages. I guess this could be any number of things including chain tensioner. It's certainly looking like once I've eliminated the injectors it's head off time.

 

Update for you guys.

Got hold of a known good injector but swapping it around made no difference to the tapping noise. So today I took rocker cover off and the only thing I've found is the two inlet tappets on number 3 are quite soft. By this I mean i can push them down with my finger. The two on inlet 5 are slightly soft but all the other 20 are solid and don't compress even when pushed with a screwdriver. Could this be the source of the noise? It's certainly in the area where the noise seems to be comming from.

 

Took the cams out today and when checked all the tappets, I have 13 that I can compress with my fingers causing oil to come out of the tiny hole on the side and 11 that feel solid and don't even compress with a pair of pliers. Does anyone know which is correct for a good tappet? squashable or solid?

Fezzalad

 

That is correct, they are hydrollic tappets and so use oil pressure to maintain the gap between cam follower and camshaft, with no oil pressure they will be soft and push in.

 

Took the cams out today and have an odd situation with the hydraulic tappets. 13 of them i can compress easily with my fingers. The other 11 won't even compress with pliers but which is right? solid or springey?

 

Sorry posted that twice as it didn't appear to post the first time.

Thanks Matthew, so you are saying the solid ones are faulty as the wont compress at all with no oil pressure? I guess I could just order a new one and see how it compares.

 

did you ever get to the bottom of this ?