Three things bring a BMW here for this. A rattle on cold start that clears in a few seconds, a whine from the front of the engine that rises with the revs, and a Drivetrain Malfunction message on the dash. We listen to the car before anyone talks about parts.
A chain gives you warning long before it gives up, and the warning is easy to talk yourself out of. Pick the one that sounds like your car and tell us about it.
You turn the key first thing in the morning and the front of the engine chatters for a second or two, then settles. By the time you have reversed out of the lot it has stopped. That short window is the tensioner waiting for oil pressure while a loose chain slaps the guides, and it is the earliest useful warning you get.
Tell us what you heard → 02Not the turbo and not the aircon. This one tracks engine speed exactly, sits low in the pitch and comes from the timing cover end. On a worn setup the chain is running against a grooved guide instead of sitting in it, and that is what you are hearing at a steady 2,000 rpm.
Book a listen → 03BMW’s own wording for a fault it will not let you drive through, and power usually drops with it. When a chain has stretched, the crankshaft and the camshafts stop agreeing about where they are, and crank-to-camshaft correlation codes such as 2A98 and 2A99 are what owners get told at that point. Bring the printout if somebody has already read the car.
Send us the message →The chain runs against plastic guide rails that hold it on its path. Those rails sit in hot oil for years, the plastic goes brittle, and the chain quietly saws a groove into the face of them. Eventually a piece breaks away and drops into the sump. Nothing dramatic happens on the day it does, which is a large part of the problem.
Once the guides are worn the chain has slack in it. The tensioner takes that slack up hydraulically, so it only works properly once there is oil pressure behind it. In the second after a cold start there is barely any, and that is precisely when you hear the noise. Every single start puts the chain through the same moment.
Singapore stacks the odds. A run to the office and back is a few kilometres, so the engine is switched off again before it has properly warmed through. Short trips leave moisture and unburnt fuel in the oil, which thins it and shortens how long it protects anything. Put a long-life interval written for European motorway driving on top of that and the oil is doing the hardest part of its job on its worst day. Crawling in traffic adds heat under the bonnet without adding any distance to the odometer.
BMW revised the guides and the tensioner on later builds, and the B48 that followed the N20 has given far less trouble. That does not make a 2013 car doomed or a 2019 one immune. It moves the odds, and listening beats assuming. If you want the background first, our guide on timing belt against timing chain covers how the two differ and why one has an interval and the other does not.
Owners rarely know the engine code, and it is the one detail that changes everything about this job. Find your model and year below.
Not sure which one you have? Send us the first ten characters of your chassis number on WhatsApp and we will tell you. The line that matters most on this table is the N47, because its chain sits at the rear of the engine rather than the front, and that single design choice is why the diesel job takes so much more labour than the petrol one.
Which one you are in depends on how long the noise has been there and what the oil has been carrying around in the meantime. We would rather tell you before you spend anything.
An early check costs you very little effort and it is mostly listening. We record the cold start before the engine has been touched, because the noise you are describing usually refuses to repeat once the car has sat with us for an hour. Then the oil comes out into a clean tray and the filter gets cut open, since plastic fragments change the conversation immediately. Then cam and crank get checked against the timing marks to see whether the chain has stretched far enough to move them. Nothing gets replaced on a maybe. If the answer is that your chain is fine, that is the answer you get and you drive off.
Leave the car with us overnight, or send a video of your own cold start from the lot. The noise we need is the first three seconds of the day, and it hides once the engine is warm.
Drained oil goes into a clean tray and the filter gets cut open. Plastic fragments or metallic glitter tell us where you are before anything else does.
On the petrol engines the chain is at the front, so the rails and the tensioner can be looked at directly. Wear grooves and cracked plastic get photographed exactly where they sit.
Cam and crank lined up to see whether the chain has stretched enough to shift them. This is the measurement that separates a noisy chain from a dangerous one.
Parts line, labour line, timeline. You look at the pictures of your own engine and decide, and nothing starts until you say so.
Chain, guides, tensioner and the seals disturbed on the way in. The old guides come back to you so you can see the wear yourself, and the work goes on your service record.
We are not putting a figure on this page. The same three words cover jobs that are nowhere near each other in labour, and a range would only mislead you before we have looked at your car. What we can do is show you every lever that moves it.
On the N20, N26, N13 and B48 the chain is at the front of the engine, reachable once the covers come off. On the N47 diesel it sits at the back against the bulkhead, so the engine has to come out to get to it. Same part on the invoice, a completely different amount of labour beside it.
Diesel kits carry more parts and the tolerances are tighter, so the hours read differently. Some older N47 components also need ordering in rather than coming off a shelf here, which changes how long your car is with us more than it changes the parts line.
Where the chain itself has not stretched, new guides and a tensioner can be enough. Where it has, putting fresh guides against a stretched chain just books you a second visit. We measure before recommending either, and we show you the measurement.
With the front of the engine apart, the water pump, thermostat, front crank seal and valve cover gasket are all sitting right there. Replacing a tired one now uses labour you have already paid for. Replacing a healthy one is money wasted, so we tell you which is which and you pick.
If plastic or metal has made it into the oil, the sump comes off and the pickup gets cleaned properly. Skipping that to save an hour is how a brand new chain gets ruined by debris left behind from the old one.
A chain job is a good moment to see the rest of the front of the engine, and we will note anything worth watching. Noting it is not the same as quoting it, and nothing lands on the invoice because it happened to be nearby.
Parts and labour listed separately, with photographs of what we actually found attached to them. Nothing appears on your final invoice that you have not already seen and approved, and if we open the engine and the picture changes, the car stops and you get a call rather than a surprise at collection. Your old parts come back with the car.
On the petrol engines where the chain sits at the front, plan on the car being with us for a couple of days rather than an afternoon. The N47 diesel is a different scale of job, because the engine has to come out to reach the chain at the back, and that runs into the better part of a week depending on parts. You get the timeline in writing alongside the quote, and we say straight away if something has to be ordered in.
We would not. A rattle that lasts a second or two on cold start is the early warning, and cars do carry on like that for months. The problem is that nobody can tell you which month it stops being a warning. If the chain jumps a tooth or a guide lets go completely, the valves and the pistons meet, and then you are looking at an engine instead of a chain. Driving gently to Kaki Bukit is one thing. Carrying on for another few thousand kilometres because it only does it once a day is a gamble we would not take with our own car.
Plenty of things rattle on a cold BMW and not all of them are the chain. A loose heat shield, a tired belt tensioner, a collapsed engine mount and carbon knock all get mistaken for it. What points at the chain is the timing of the noise: front of the engine, first few seconds after a cold start, gone once oil pressure comes up. That is why we ask for the recording. A noise that only turns up under load, or only at one road speed, is usually somewhere else entirely.
No. It sits in a few engine families rather than across the whole badge. The N20 and N26 petrol fours built roughly between 2011 and 2015, and the N47 diesel before about 2014, are the ones that come up most. BMW revised the guide and tensioner parts on later builds, and the B48 and B47 engines that followed have behaved much better. An older car with a full oil history can run a very long way without any of this, and a neglected one can give you the noise early.
No. Singapore’s Competition and Consumer Commission had the authorised car dealers drop the warranty terms that tied servicing to their own workshops, so a claim cannot be refused simply because an independent did the work. Cover stands as long as compatible parts are used and the manufacturer’s procedures are followed. We do both, and the written report is your record of it. There is more in our piece on servicing under warranty in Singapore.
The camshafts stop turning in step with the crankshaft. On these engines the valves and the pistons pass through the same space at different moments, and that timing is the only thing keeping them apart, so when it goes the valves get struck. Bent valves, marked pistons and a scored head are the usual bill, and on a bad one the head comes off and the block is a question mark too. That is why we treat the rattle as this week’s job rather than something to watch.
A chain, if it was built any time in roughly the last two decades. BMW moved its mainstream petrol and diesel engines off belts long ago, which is why there is no belt interval in your service book to prompt you. A chain is built to last the life of the engine, and that is exactly why owners get caught out when the plastic guides around it do not.
Oil leaks, cooling and water pumps, carbon on the intake valves, servicing intervals set for our weather, and the models we take.
Back to the BMW page →Where the work goes when a chain has already done damage. Diagnostics, strip-downs and rebuilds, quoted only after we know what is wrong.
Learn more →How the two differ, why a chain has no interval in your service book, and what to listen for on either one.
Read the guide →