Engine start up noise when cold

[HeolBwr]

i have a 2011 C Class 1.8 Auto Cgi sports estate that has done 58,600 miles.
M271 DE 18 AL red. N/A 82.0 x 85.0 115 kW at 5000 rpm 240 Nm at 1600-4200 rpm 2009-12 W204 C 180 BlueEfficiency
Engine start up noise which last a few secs then disappears. took it to Mercedes dealership diagnosed and the changed the timing chain and tensioner.
Net result after spending £1200 the noise is still present. Can someone identify what else would cause this noise.

 

[markjay]

The noise may be normal, it can take a couple of minutes for the oil pressure to rise sufficiently to fully lubricate the hydraulic tappets.

As for the new timing gear, it is not a waste, the M271 engines do suffer from fatal failures due to premature timing gear failure, so having the timing gear replaced should buy you peace of mind for a few years at least.

 

[grober]

Depending on the noise it might just be the alternator overrun pulley* thats driven by the poly V belt or possibly the belt tensioner pulley itself. The poly V belt is loaded up after engine start up as the alternator puts out a bit of high current for a short time to quickly recharge the battery. Best way is remove the poly V belt and check both pulleys for wear- just search m271 poly V belt tensioner /alternator on You Tube

*sometimes alternators just squeal [ its a distinctive sound -not a "chatter/rattle" you might get with tappets]when loaded and there's nothing wrong

 

[HeolBwr]

The noise may be normal, it can take a couple of minutes for the oil pressure to rise sufficiently to fully lubricate the hydraulic tappets.

As for the new timing gear, it is not a waste, the M271 engines do suffer from fatal failures due to premature timing gear failure, so having the timing gear replaced should buy you peace of mind for a few years at least.

Thanks but been down this "normal route" But you're right about replacement being of value

 

[HeolBwr]

Depending on the noise it might just be the alternator overrun pulley* thats driven by the poly V belt or possibly the belt tensioner pulley itself. The poly V belt is loaded up after engine start up as the alternator puts out a bit of high current for a short time to quickly recharge the battery. Best way is remove the poly V belt and check both pulleys for wear- just search m271 poly V belt tensioner /alternator on You Tube

*sometimes alternators just squeal [ its a distinctive sound -not a "chatter/rattle" you might get with tappets]when loaded and there's nothing wrong

Thanks, as the vehicle is still in garage I'll get them to check this.

 

[HITECH]

£1200 replacing a timing chain. I would for defenete get the v belt changed aswell regardless of when it was last changed. Then it is ruled out. Plenty of engine faults/noises caused by a bad/cheap/worn aux belt. 1 thing to simply rule out. They will get a proper visual inspection of all the pulleys once the belt is off but dont be fooled by the old yeah that tensioner seems a bit wobbly LINE. Get the belt replaced 1st then discuss.

 

[HeolBwr]

Thanks, as the vehicle is still in garage I'll get them to check this.

Depending on the noise it might just be the alternator overrun pulley* thats driven by the poly V belt or possibly the belt tensioner pulley itself. The poly V belt is loaded up after engine start up as the alternator puts out a bit of high current for a short time to quickly recharge the battery. Best way is remove the poly V belt and check both pulleys for wear- just search m271 poly V belt tensioner /alternator on You Tube

*sometimes alternators just squeal [ its a distinctive sound -not a "chatter/rattle" you might get with tappets]when loaded and there's nothing wrong

Hi just seen this on you tube, same as my vehicle, same noise. Do you still think it may be the alternator overran fully arrangement ?

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[grober]

In the first start up its sounds like normal timing chain/tappets in the second the same again plus a bit of alternator whine. Sounds pretty normal to me. Of course it depends on how loud/ persistent it is. Listening to an engine with the bonnet open without the benefit of bonnet and bulkhead sound deadening is always going to be louder than inside the car with the bonnet shut?

 

[HITECH]

If wrong aux belt has been fitted. couple of mm smaller than whats supposed to be on it then its straining every single pully on the engine and too tight. If its correct size but a cheapo make then again it still could be too tight. If you already changed the aux belt with a decent one then ignore my babbling. if you havent then it is the 1st port of call to do. As said before it all sounds different when ur under the engine to when ur sitting in the drivers seat. If ur driving in a confined area with ur windows down how audible is it ? That is usually best way to guage the volume of an un-explained not normal noise on your car. If its engine noise of some sort then dump all ur all out and stick new filter and oil into it. If u trust who has done every bit of work to it then ignore me then. Good luck.