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N47 Diesel 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
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.
BM Bitz Ltd
BMW Group UK
08000 935 656