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N47 Timing Chains

A new problem has been arising lately with N47 BMW diesel engines,

so in the first of a new series we're taking a focused look at the issue in hand.

 

If you've ventured on to the internet lately and come

across one of the many BMW forums that covers

diesel variants then you may have seen their rise in

posts regarding timing chain failures. It’s a relatively

new issue that's only started to come to light on a

regular basis in the last year or two, and it's a problem

that only affects diesel engines coded N47D20A and

N47D20D made in a certain time period.

This engine was introduced into the range in March

2007, debuting first of all in the E8x 1 Series

and then in September that year it found its way into the E9x 3

Series and E60 5 series too.

 

At first all seemed to go well. The all-alloy engine

offered good performance and economy, but then an issue started to arise

with a crucial part of the engine - the timing chain.

This is one of the most important parts on the engine as it's used to keep all

of the cylinder head's inner workings in perfect unison

the moving parts of the blocks internals

and results of a failure are catastrophic.

Whilst issues with mass-produced engines can be

expected from time-to-time, unlike the well documented swirl flap issues of previous diesel

engines, the cause of the timing chain problem is still

an unknown. There are theories as to why the chain

fails, built it appears nothing is known for sure,

although it does seem to stem from the actual chains

themselves stretching, and then snapping.

But worse still there seems to be no real correlation

in the pattern of failures.

 

There are reported cases of

chains going with little or no warning and when the

engine is merely ticking-over or whilst driving along a

motorway at a steady speed. Even mileage is a factor

that varies massively, with owners reporting  failures on cars showing as low as 26,000 miles

whereas others go having covered over 100,000. And furthermore,

consistent and regular service history doesn't seem to have an effect either in a good number of cases.

As you might imagine, a failure is costly to fix and the amount of damage will occur to the valves

and camshaft carriers and will require a new timing chain guides and tensioners. And that's if your lucky

as the camshaft itself can also be terminally damaged and often complete engines are written off.

To make matters worse, the cost and difficulty of

the job is made much by the chain's position

on the engine. Previously, timing belts and chain

setups have always lived on the front of the engine

where they are relatively accessible for maintenance

such as a check upon change.

 

 

However , for the new N47 diesel engine, BMW

completely redesigned the timing chain setup and

relocated it to the rear of the engine by the bulkhead area.

This was done largely on the principle that the chain was to become a service-free item, and

therefore was the best situated out of the way. But as a

result, gaining access to these parts is much more

difficult, labour intensive and therefore expensive. In

fact, it requires the engine to be removed completely

as it can be done in situ.

BMW itself seems aware of the problem. Indeed,

you may well have seen a piece on the BBC 1

program Watchdog regarding the issue of failing

timing chains on these engines. Even so, BMW

address these problems as isolated incidents, but in

May 2009 modifications to the timing chain setup on

these engines were made at the factory and problems

since seem to have virtually diminished.

 

 

BMW's official response to the BBC report

'BMW offers a comprehensive, full three-year warranty

on all new cars sold in the UK. Outside of this warranty

period, while there is no obligation to assist with the

costs of repairs, BMW operates a generous goodwill

policy and will consider financial help, depending on

the specific circumstances of each case.

'Reviewing the customer cases which you have

mentioned, the circumstances of each vary widely, as

has the response from BMW. Where a fault has

occurred on a vehicle with relatively low mileage,

which has been serviced within the BMW network,

the company has covered most of the repair out of

goodwill, despite being outside the warranty period,

'Older vehicles which have not been serviced or

repaired by BMW-authorised technicians where there

can be no certainty as to the quality of the work done

or whether genuine BMW parts were used are

typically not covered.

 

The use of non-genuine parts,

which don't match BMW specifications, can actually

damage other components in the car or harm the

performance of it's vital systems. Whilst we appreciate

the disappointments this will have caused, we cannot

provide an indefinite guarantee against engine or

component failure, as no manufacturer can.

"BMW is committed to ensuring the best possible

customer satisfaction and takes all customer concerns

extremely seriously. In the case of unusual engine

noise, or a more serious fault, there can be a wide

variety of causes and further information is required

before any conclusion can be reached. If any of your

viewers is concerned about their car following your

programme, they should call BMW Group UK directly

on 08000 935 656, where we would be happy to

advise them."

 

 

Will it happen to my engine?

First of all, as mentioned this only affects the

N47D20A and N47D20D engines which were built

from March 2007 to May 2009, so if your car doesn't

fall into this category there's no cause for concern.

However, if you do have a diesel engine matching

this criteria then there is usually a tell-tale that

failure is imminent by listening carefully for any metallic,

rattling or ticking sounds, particularly at the rear of the

engine. Reports are it happens intermittently at first

and tends to disappear before occurring again as a

more permanent sound that will then grow louder.

Any foreign noise should be looked at by a

specialist or main dealer straight away who should be

able to diagnose whether it's the timing chain or not.

Sadly, due to the awkward positioning of the chain

at the rear of the engine there are no preventative

measures that can be undertaken to ensure it won't happen

other than to replace the entire setup,

including the chains, tensioners and guides. This is

still labour intensive and costly affair that will require

many new parts and service items.

 

 

How much does it cost?

It depends on whether a specialist or a main dealer

does the work, but the bad news is that no matter

what, it's probably going to be costly.

In a scenario where the chain has already failed

and damage has been caused to the cylinder head's

internals then expect to pay around £1200 in labour

charges to remove, rebuild and refit the engine and

another £1000 to cover parts. That's from a well-

reputed, independent specialist such as BM BITZ in

Essex but prices can vary depending on damage.

If the timing chain setup is changed as a

preventative measure before it fails then parts should

work out nearer the £700 mark but labour remains the same.

 

If you want to take the car back to BMW to repair

then expect to pay double that overall figure and

more, again depending on the damage. Average costs

seem to be nearer the £5000 mark and we've heard

of bills as high as £8000 and above where full,

replacement engines are deemed necessary.

 

Thanks,

 

BM Bitz Ltd

01268 683790

www.bmbitzltd.co.uk

 

This Article appears in both BMW CAR MAGAZINE &

PERFORMANCE BMW MAGAZINE

 

PLEASE CLICK HERE TO READ THE FULL WATCH DOG REPORT

Bm Bitz Ltd

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