So, I got this ratle sound on my DSE, that comes up around 2.600rpm. It is doing it stationery or moving. The rattle seems to drop a bit once going over 3.000rpm and if I take my foot down it keeps on rattling until around 2.400rpm, than everything is quite as normal (as quiet as diesels can be...). It sounds like something is getting to it's natural vibration frequency and then starting to make noise.

A friend that heard it doing this says that it could be the timing chain tensioner that is faulty, so I looked into it. But, after reading everything on RAVE about the timing chains, I can't get my head around how the tensioner works. I know it pushes the tensioner arms against the chains, but how does the tensioner itself work ? Is it hydraulic operated, from the oil pump pressure ?
If I'm correct in this assumption, then the pieces that come in contact with the tensioner arms act as pistons, and there has to be an oilway from the engine block into the tensioner itself, that provides pressure to operate the pistons.

Is it something like this:




And, for the 2nd question, if it is hydraulicly operated than replacing this certainly won't cure my rattling problem, because there's no way this piece could have failed.... ?

Surely it's explained in RAVE?

Dear Data,

As much as I like chatting with you fine people over here at LZ, I wouldn't have asked if I could find it in RAVE. As I stated, I searched for and read everything about the timing chains and tensioners...

mcapinha said:

Dear Data,

As much as I like chatting with you fine people over here at LZ, I wouldn't have asked if I could find it in RAVE. As I stated, I searched for and read everything about the timing chains and tensioners...

Click to expand...

Well if you read up on how to change a cam shaft, you will note there is a special tool called up to retract the chain tensioner and special pins to put in it to hold it back. So one should assume from that and from the photo you posted showing retaining pins in place that there is some spring loading involved. Which is in fact the case.

Well, to be honest, I didn't come to that conclusion. I read about the special lever tool but I assumed that it was needed only as a way to push the guide arms. But after reading your comment and this BMW Workshop Manuals - 5 Series E34 525tds (M51) TOUR Workshop Manual - 3 RA Replacing Both Timing Chains (M51), it is now obvious that the pistons are spring loaded and not hydraulic. (It's becoming ever more obvious as I write it.. if they were hydraulic there would be no pressure with the engine off and thus no force to push the chains).

Thanks for the input


So... it is feasible that the tensioner's springs can become worn and it should be replaced.

mcapinha said:

Well, to be honest, I didn't come to that conclusion. I read about the special lever tool but I assumed that it was needed only as a way to push the guide arms. But after reading your comment and this BMW Workshop Manuals - 5 Series E34 525tds (M51) TOUR Workshop Manual - 3 RA Replacing Both Timing Chains (M51), it is now obvious that the pistons are spring loaded and not hydraulic. (It's becoming ever more obvious as I write it.. if they were hydraulic there would be no pressure with the engine off and thus no force to push the chains).

Thanks for the input


So... it is feasible that the tensioner's springs can become worn and it should be replaced.

Click to expand...

It is feasible that the tensioner arms are worn away.

From the pictures I found online I understand what you're getting at. If they are worn away, beyond the maximum opening of the tensioners pistons, the chains will become loose.
But I'm beginning to think that this may not be the problem. If they were getting worn than the problem should present itself gradually and not so sudden as this.

Oh the joys of P38 ownership.

The guides are coated when that wears out you loose tension and that's when the trouble starts as the metal chain can come in to contact with the guide itself or its Aluminium case