TheMayer

Hey everyone,

I have been researching the M271 timing chain issues since I picked up my c230k a few months ago and started hearing a noise on a cold start for 1-2 seconds. I am ready to pull the trigger and replace the chain but I had a thought that I wanted to run by someone who knows more than I do.

I've heard other motors (a new Toyota Venza for example) make the same noise and was told that it was the "cold start valve" helping the cold oil come up to pressure quicker.

Is this "valve" even a real thing, and if so does the M271 have one that would make the sound usually described as a chain at the end of its life?

slk230red

I was waiting for a C class member to post, but I'll go ahead and give my opinion. I'm 99.9% sure that the noise you hear at cold start-up is the magnetic cam adjuster. Google it.

My 2001 SLK230 has made the noise since I bought it new. It seems make less noise after oil changes at 5k intervals. Mobil 1 0-40w of course.

VVF

It could be the cam adjusters (2 on M271), or the lifters, or the chain, from my understanding.
How many miles on the engine? From the statistics on this forum it looks like if it made it past ~120k miles with no chain problems then you might be ok.

TheMayer

I've been trying to read up on the cam adjusters as well, I honestly just can't determine which sounds like a more probable cause. I'm used to my old Jeep's pushrod I6, all this DOHC talk is new to me, haha.

The motor has 141k miles on it as of now. I bought it when it had 136k and I have no real idea what work has been done to it in the past. I bought a history report and it showed religious dealership maintenance until 96k where it was brought into a euro shop for "replace battery, vehicle serviced." It was then sold and it seems the next owner did their own services and drove it until I picked it up at 136k.

Thoughts?

Glyn M Ruck

If you hear a rattle from the front chain case at cold start up after the car has stood overnight that shuts up after a few seconds as the oil pressure rises it is 99% certain you have a stretched timing chain. If you want to prevent bending all the valves you should immediately pull a new timing chain & fit a new use once timing chain tensioner element.

The cam adjusters can rattle. There is a deburring procedure that does not work. Replacement is the only answer.

I would replace the timing chain pronto!

This should be a service item on the M271

jpman

I always find all the information glyn provides on point. However, I'm not sure if I'd call it a service item. I believe there was a defect with the original chain. In my timing chain post or I believe the one hogger made I showed different part number for chains and also difference in physical aspects. Also I had the original and new chain side by side, and there is definitely a difference in thickness a small one at that. My chain was not stretched at 114k miles.

RWDlifer

Mine had the rattle, changed out the chain which was stretched 2mm, and it still rattles sometimes after sitting overnight...
What I've also noticed is that the rattle is inconsistent on mine. I've had the car sit undriven for over a week and it started without a rattle, and that was on a chilly 30-something degree morning...

Glyn M Ruck

These engines should never have been built with simplex chains. They continue to give trouble even with the latest chains.

You might have a damaged guide rail or it might be a slightly messed up cam adjuster. Presume the new tensioner element was released correctly.