1 Series (E87) - petrol - timing chain TENSIONER

[aph202]

Hi,

We've an '05 plate 118i. A garage recently changed the oil sump oil seal. In removing the sump they "found" a length of the plastic timing chain tensioner.

They told me that replacing the tensioner (which I assume is the one located between the top end and bottom end of the engine, rather than the one at the top) is a massive, engine-out job. It was therefore left and the engine is running fine for now.

I've seen some information though that this isn't a massive job at all and is in fact about an hours worth of work, in which case, well worth getting sorted(!!)

Anybody know about how big a job this is? Is disintegration of the chain tensioner common?

Is the chain at the front or back of the engine? (I know it's the back on the N47)

Thank you,
Adrian.

[helix402]

Changing the tensioner is a 10 min job. In the case of your car the guide rail has broken. Changing this does not require engine removal but is an involved job. A new tensioner should be fitted at the same time. I have a one new guide rail for this engine, if you want it for a small fee drop me a message.
If you continue to run with a broken guide rail or original tensioner the chance of the timing slipping is high. The tensioner is at the front of the engine, drivers side.

[helix402]

Here's one with a slipped timing chain.

[aph202]

Thank you, this is very helpful.

I'm no mechanic myself, so when you say quite involved, what might we be talking about hours-wise at a good specialist?

I'm assuming a slip has the potential to be as disastrous as a break?

Thanks again,
Adrian.

[helix402]

The time for the repair depends on which guide has broken. Some are easier to replace than others. I expect some specialists will only want to replace a complete timing chain and guide kit. If the timing slips you will experience a large knocking sound (timing chain hitting cam cover) and a major lack of power.
You could try just fitting a modified tensioner and see how it goes. Book time for a full timing chain replacement is 7 hours.

[iSore]

The N42 and it's replacement the N46 (virtually identical) are known for timing chain problems. To fix it is a days work on a ramp - the sump needs to come off because unlike most engines such as the M111 Mercedes unit (similarly crap) the front timing cover doesn't come off. Instead, the chain and tensioner rails fit kind of like a cassette down into the front of the engine. You'll need a chain and tensioner guide rail set and to do the whole job you're looking at around £500. I would also consider replacing the crank sensor whilst it's there as these fail - with the engine all back together it's almost impossible to replace.