N47 (and related N57 etc) timing chains
Discussion
Hi,
I have not seen it mentioned specifically what fails or wears out prematurely on the N47 and N57 timing system.
Is it only the chain?
Are the sprockets susceptible to wear?
Are the sprockets one piece with camshaft or can they be replaced separately and thus retain the existing camshaft?
Do the repair / upgrade kits resolve the problem? e.g. say someone purchased a car and allowed for a chain replacement kit and fitting in the purchase budget and then had the work done post purchase, would this kit fix the risk / problem?
Thanks,
I have not seen it mentioned specifically what fails or wears out prematurely on the N47 and N57 timing system.
Is it only the chain?
Are the sprockets susceptible to wear?
Are the sprockets one piece with camshaft or can they be replaced separately and thus retain the existing camshaft?
Do the repair / upgrade kits resolve the problem? e.g. say someone purchased a car and allowed for a chain replacement kit and fitting in the purchase budget and then had the work done post purchase, would this kit fix the risk / problem?
Thanks,
The original n47 camshafts had machined sprockets that were overly sharp. End result chain stretch, tensioner unable to cope with that and bye bye top chain. Equally some did not just simply stretch but snap.
In addition the design of the guides was not helping things in absorbing the noise and stretch of the chain, so the updated guides have an infill section instead of the ribs.
In fact most of the final n47 timing was used in the b47. Some of the b47 engines have now also began to show some issues with stretch and in some cases some of these engines fail to feature all updated timing chain components.
The n57 is slightly different as it never featured the machined element, but the top chain can still stretch (and so can the updated n47 ones). In fact read around and you will find most manufacturers at some point in recent years have struggled with timing chain stretch and a tensioner that is simply not up to the job.
The lower chain for both engines seems generally less problematic, but obviously if the top fails it screws a lot of the top end.
I think the major issue is sorted, but people, rightly or wrong, need to get a clear view that many timing chains do stretch and in many cases extended service intervals simply make everything worse.
In addition the design of the guides was not helping things in absorbing the noise and stretch of the chain, so the updated guides have an infill section instead of the ribs.
In fact most of the final n47 timing was used in the b47. Some of the b47 engines have now also began to show some issues with stretch and in some cases some of these engines fail to feature all updated timing chain components.
The n57 is slightly different as it never featured the machined element, but the top chain can still stretch (and so can the updated n47 ones). In fact read around and you will find most manufacturers at some point in recent years have struggled with timing chain stretch and a tensioner that is simply not up to the job.
The lower chain for both engines seems generally less problematic, but obviously if the top fails it screws a lot of the top end.
I think the major issue is sorted, but people, rightly or wrong, need to get a clear view that many timing chains do stretch and in many cases extended service intervals simply make everything worse.
I've been led to believe that the problem stems from BMW using a substandard timing chain that stretches more than it should. When it's stretched it tends to move sideways enough to chip of small pieces of the plastic timing chain tensioner guides. These small pieces then plug the oil passages with the eventual demise of the engine. That is if the timing chain doesn't snap first, and as I believe it's an interference engine, it can get expensive really quickly.
bmwmike said:
Doesnt seem to be a problem on the petrol six pots. Wonder why that is.
Yes it is. Not as common but still a problem. The chain is very skinny compared to a proper one as fitted to the old M prefix engines. Four cylinder engine es are harder on chains that sixes due to the firing pulses. Touring442 said:
bmwmike said:
Doesnt seem to be a problem on the petrol six pots. Wonder why that is.
Yes it is. Not as common but still a problem. The chain is very skinny compared to a proper one as fitted to the old M prefix engines. Four cylinder engine es are harder on chains that sixes due to the firing pulses. bmwmike said:
Touring442 said:
bmwmike said:
Doesnt seem to be a problem on the petrol six pots. Wonder why that is.
Yes it is. Not as common but still a problem. The chain is very skinny compared to a proper one as fitted to the old M prefix engines. Four cylinder engine es are harder on chains that sixes due to the firing pulses. Replaced it with a Z4 with an N52 engine and liked it so much I ended up buying a 3 Series with an N52 as a daily. But I left the alert on Autotrader running and over the course of a couple of years I did see a couple of N52 engined 325is for sale as Spares or Repairs with cam-chain issues so it seems it can be a problem, but not on anything like the scale of the N47 engines.
Touring442 said:
bmwmike said:
Never heard of any timing chain dramas on n52 or n53, n54 nor n55. Which are you referring to? The newer b engines perhaps.
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