Engine rattle at low revs and under load

Hello all, this is my 1st post so go easy on the new guy.

I have a '99 (T) 318is with 63k on the clock and I'm more than happy with it other than one problem -

I have for some time now had an annoying sound coming from under the bonnet. At idle and under load (up until about 2500 / 3000 rpm). I've had a few people look at it and have had a number of differing opinions on what it might be. These range from a bad tappet -         (I think this is another problem to be honest), a damaged cam, and the timing chain or guide rails.

I was wondering whether anyone on here has experienced anything like this before and has a solution - I obviously don't want to fork out for one if it's something else. I've been quoted £500-£600 for the cam and tappets which is quite good but which might also be unneccesary to solve this.

Thanks for any help.

Rob

Hello again,

I had a look at the manifold and couldn't see any sign of a crack/split. Took it down to the local Independants where it is serviced, and they were certain it was the tappets and not the chain - so I booked it in with them for last Wednesday (£350). Wednesday 10 O'Clock ish, they rang up to say that their special tool had fractured and had another one coming in tomorrow so I left the car overnight with them. Then on Thursday, they rang to tell me that they had had 2 different sets of tappets in and it was still noisy. The guys at the garage are fantastic, and it just seems that these things always happen to me. They were very fair though and said they admitted liability for the tappets.

It is still there with them and they say the only thing they can do is strip it bit by bit, and examine the parts as they come out one by one to look for damage.

However, I have come across a post on t'internet that mentions a purge valve fitted to the mounting that can cause the exact sound as a bad tappet and needs a rubber mounting fitting to move the offending valve away from the body of the car. Admittedly this was in respect of an M52 engine. My question is whether there is a similar thing in an M44 engine as I am unable to check for myself at the moment. Here is the post - http://jackassofalltrades.com/ticker.html 

Thanks for your help

Rob

b38isp - To be honest, I really don't think these guys would fleece anyone. I have taken 2 of my cars to them for years and they have been really 1st class in every aspect. It might be that I heard them wrong although they had two cam sprockets out on the frint window and said they were fine, but there was a lower one that was worn (maybe a different sprocket, but definitely a lower sprocket) and then he said there was something breaking down inside the follower - again I might have misheard and be wrong about the needle.

I really wouldn't want to give these guys bad press as they are very professional.

As for the tappets, they were convinced after hearing it that these were the culprits and replaced them - as they were not faulty he has not charged me for them at all. That said - I will wait until I get the car back fixed and with an invoice before I praise them too much.

RossiS - Took the heatshield off my last one as I had a similar problem - this is definitley something more substantial though. Thanks for the post.

Cheers

Rob

This isn't pinking is it?

Only happens under load at low revs and sounds a bit like a rattle??

I would be careful before spending a fortune.

£1500 for a new engine?? 25k more than yours is 88k so IMO £1500 is far too much.

Pinking is:

Knocking (also called pinking or pinging)—technically detonation—in internal combustion engines occurs when fuel in the cylinder is ignited by the firing of the spark plug and smooth burning proceeds but some of the unburned mixture in the combustion chamber explodes before the flame front can reach it, combusting suddenly before the optimum moment of the four-stroke cycle. ...

Also:

Knock at low engine speeds is called ‘pinking’ or ‘pinging’ and can be detected by a high pitched jingling sound inside the engine. Knock at lower engine speeds generally doesn't cause much harm.