spb147

Hi,

my cars been experiencing a loud rattle at low rpms for a while now (two YouTube links attached below). usually after 30 mins of driving, the car makes a loud rattle at around 1250 rpm.
the longer the distance I travel the louder the rattle becomes and going either uphill or downhill exaggerates/increases the sound.

regardless of whether I'm driving or have the car parked in N or P, the car makes a rattle at about 1250rpm.

any suggestions or help will be greatly appreciated, this is driving me crazy think my car will break down at any moment during long drives.

Odd Piggy

Can’t really tell from the audio in the vids on an iPad.

I’m going to assume the oil level is okay. Rattling regardless of whether you are in P, N, or D at a specific RPM means something (rotating?) either attached to or inside the engine. Search “W271 timing chain” on this forum and head to your nearest independent Mercedes Benz specialist for a professional diagnosis. If it’s the timing chain and it jumps a cog or two, your “my car will break down at any moment” fears will come true.

It could be a number of other things:
Serpentine belt idler,
Serpentine belt tensioner,
Water pump,
Some other pulley,
Exhaust component interference,
Loose bolt on the A/C compressor,
Loose bolt on the power steering pump,
Something else that has come loose,
Timing chain tensioner,
The list goes on.

But if it’s a “stretched” timing chain, you can’t afford to assume it’s something else and be wrong. That could destroy the engine.

AAIIIC

The fact you're listening on an Ipad isn't the issue; I'm on a PC with external speakers and can't hear anything other than just normal engine noise.

Concur with everything you said about what the rattle could be and what the possible consequences could be.

spb147

thank you for the feedback. I apologize for the poor video, I will post a better video soon

spb147

Hello,

Ive attached two better videos capturing the rattle - one from the engine bay and one from inside the car - the noise is much clearer since its in the garage without any outside noise.

it doesnt sound to me like it coming from the from of the engine (ie from the camshafts or timing chain) but I could be completely wrong. To me it sounds like its coming from the back of the engine and more from the right side of the engine bay. the noise starts to come on after about 30 mins of driving. the noise is there whether its in Drive, park, or neural (not sure if that completely rules out the transmission as being the culprit) but I hope its not do with the transmission, timing chain, guides or tensioner.



Inside the car

from engine bay

any help or suggestions would be greatly appreciated!

Thank you again

Odd Piggy

These sound clips are much better.
How many miles are on your C250?
Your car makes a lot more noise than mine with 100k miles. Your turbo seems very loud but maybe it’s the sensitivity of the smart phone mic.

The ratcheting sound “could” be the timing chain, but maybe not. You say it comes from the back right hand side of the engine. That could be the oil pump. Noise from the oil pump is usually no big deal. But, as I said in an earlier reply, the timing chain is not.

I really don’t think it’s your cam phasers because they make an unmistakable racket on start up then quiet down. And the problem is almost never the tensioner by itself. To me, it doesn’t have the characteristic noise of the transmission pump going bad (usually more of a buzz than a rattle).

If it’s the oil pump, changing oil viscosity (maybe 5w30 to 5w40) or even brand (Mobil 1 to Castrol Edge) could make a difference. I run Mobil 1 0w40 Euro, but my grandson’s BMW 335i rattled like it was coming apart until we switched to Edge 5w40. No mechanical work was needed — go figure.

Noises under the hood are difficult to locate with the naked ear. There is a car stethoscope with a long thin probe that does a good job of pinpointing them — valve train noises, exhaust manifold leaks, timing chain rattle, various gear noises, A/C compressor, pulleys, etc. You can pick one up at an auto parts store and do it yourself, just be very careful of rotating parts. Or you can take it to a mechanic, which I suppose you’re trying to avoid.

While you’re investigating, I would avoid pushing it to red line. A C250 hits nearly 7000 RPM on upshifts at WOT. I hope that helps a bit.

spb147

Thank you for your reply!
The car currently has 71.5 miles (115k kms); the sound has been present since about 30k miles and has never had any other symptoms like loss of power or throwing out codes or lights. It comes so intermittently that I didnt get it checked out while the car was still under warranty which in retrospect was very stupid of me

To me the sound doesnt seem like its coming from the front of the engine/ camshaft or timing chain areas (hopefully I'm not wrong on this). its significantly louder towards the back of the engine bay (it may be audible enough from the video above from the engine bay at the 10sec & 50sec mark) - its the loudest ive ever heard it from the video from inside the car at the 40 sec mark
I changed the cam phasers and timing chain tensioner a few months back under the extended warranty and that solved my start up rattles and long cranks.
I currently use mobil 1 0w40 euro. I may as well change the oil brand next time.

I will take it to my mechanic In a few weeks, in the meantime I scoured the threads to see if anyone had the same issue as mine to have an idea of the issue when I visit the mechanic

And I came across another relatively nonactive thread that experienced the same exact issue.
https://mbworld.org/forums/c-class-w...e-problem.html

what they seem to have found is the noise coming from a plug coming loose from the oil pump chain tensioner- ive also posted there, hopefully they'd respond.

Odd Piggy

Your phasers have been changed so that issue is covered. There is a high pressure fuel pump warranty on these cars, but I’m not at all familiar with the precursors to the failure.

I’m just concerned about the general high noise level of your engine. We can’t compare passenger cabins because mine is a luxury model sedan with premium package. But with the hood open they should be the same. When mine is in the garage with the hood up, it makes a lot LESS noise than my wife’s sewing machine. The only thing that can be heard is the high pitched ticking of the valve train. Give the Castrol Edge 5w40 a try, I’m pretty sure it’s on the BeVo. Long shot, but it’s inexpensive relative to a mechanical repair, and it worked on the 335i.

Keep us posted.

spb147

other than the rattle, i can't really comment on the loudness of the engine since I haven't heard other m271 engines.
Does the loudness of my engine by chance sound like a timing chain ticking to you? the timing chain wasn't replaced when the phasers and tensioner were.
and I will definitely try changing the oil.
thank you again

Odd Piggy

The ratcheting noise heard starting at about 12 seconds on the engine bay clip then occasionally throughout might be the chain. But it may not be because chain slap should get progressively worse as RPMs increase. I had the chain replaced with the phasers on the advice of 2 factory trained mechanics. But if it is the chain, that’s definitely not the end of the car. The chain can be replaced by only removing the valve cover and replacing the tensioner. That’s not terribly expensive. The front cover does not need to come off (it’s under the head!), the crank sprocket and guides do not need to be replaced.

My C250 is on long distance duty right now. But when I can get it back (hopefully in a few days), I’ll record it with my phone and compare it to yours.

spb147

great! thank you

So for the timing chain replacement, the entire front covers don't have to come off?
I was quoted ~20hrs of labor to do the timing chain by my local Merc dealer when I was contemplating replacing the chain out of pocket while they were replacing the phasers and tensioner under warranty; they even said chain replacement is an engine out job.

Odd Piggy

Nope. Not unless you insist on changing crank sprocket and guides. That front plate is bolted to the head and the block. It’s a real PITA. I don’t know what’s in the WIS, but I can’t imagine it’s engine out even there.
They changed my timing chain by splicing the new one to the old one using 2 techs to feed the new one in while pulling the old one out. Then with the cams still locked from the phaser replacement, the new chain was linked together and the engine was already timed. Total job (including phasers) was a little over $3k and about $1600 of that was parts. No where near 20 hours labor.
If you need a chain replaced, find an indie shop flying an MB flag and check their references.

spb147

awesome, will do and will update this thread asap

benyapzl

hi, i got the exact same problem as you.

i changed idle tensioner, timing chain, both exhaust and intake cams, propeller shaft bearing, overhaul my gearbox 3 times (new clutch, new torque converter) with new TCU (i thought was gearbox issue).

But nothing was solving the problem..

so i seen the other thread, it boils down to 2 problem.

1) tensioner plug drop off
2) brake vacuum pump.

Option 1 needs the engine to be remove.
option 2 is cheaper.

i cant decide which option to try. i have spent tons of money giving the amount of parts i changed including gearbox.

spb147

Yup, according to the other thread, linked below, the most likely culprit is the brake vacuum pump as multiple people have fixed the issue by replacing the part, this is consistent with where I hear it the loudest in the engine bay though I can't begin to fathom how this could be causing this noise. this seems like a significantly more common problem than previously thought - not sure what the long term adverse effects could be.

I will replace the brake vacuum pump since its a relatively cheap job and hopefully that fixes the issue. will update once I do so.

https://mbworld.org/forums/c-class-w...problem-2.html

Sid23

hi! Did the vaccum pump change solve the issue? I changed mine and it hasn’t. I was told on the other forum that it’s the hose attached to the pump but the spare parts store near me does not sell that hose. Waiting to get it from elsewhere.

spb147

quick update, I just took my car in to the mechanic and replicated the sound by holding the car at around ~1200 rpm while they listened with a stethoscope - they said the brake vacuum pump (which some have found to be the culprit for some in the post below) was quiet and they said the rattling noise was coming from the exhaust manifold gasket.

I don't know how that could explain the rattling noise, and that it's contrary to the brake vacuum pump solution thats worked for some https://mbworld.org/forums/c-class-w...problem-2.html

If anyone knows whether or not the exhaust manifold gasket could be a plausible explanation for the noise, id appreciate your input!

Odd Piggy

Well, if the gasket is loose and leaking, or if it has a crack in it, or if the base of the manifold itself is cracked, those can make considerable noise.

But here is the next place I would look based on experience from the 90s. If anything from the road has hit the catalytic converter hard, the monolithic catalyst can break. It sounds just like something loose under the car or in the suspension.

Bang on it lightly with a rubber mallet. But not hard! You don’t want to break s good one! If it rattles, there’s the culprit.

spb147

thanks! ill test out the catalytic converter next
would this still be consistent why theres only the rattling noise at a certain rpm range?
edit: I also forgot to add that the car shakes ( I can experience this from driver seat) while at that rpm range

Odd Piggy

My converter rattle was speed dependent, so maybe RPM too. That car didn’t have a tach. It rattled horrendously at 25, again but less at 50 and 75, so maybe some kind of harmonic(???).

Converter didn’t make the car shake, but if car shakes for whatever reason at that RPM, it might shake the converter.

It’s very easy to check, so maybe do it just to eliminate that as a cause.

Finding rattles is like chasing ghosts.

spb147

so far its hasn't affects performance or thrown any codes. I was just worried, perhaps naively, that it may somehow be the camshafts rattling inside.
thanks again! I'll check out the cat and update this post.

benyapzl

to me i feels its the cam shaft, tappets or timing chain? it just felt that there wasnt pressure thats why the parts rattle

mtaani

please let me know what did you found about that noise my car car the same problem i took it to Mercedes dealership few times the last time they took 3 months looking for that issue and this is what they did trying to fix it
replaced vacuum pump
replaced camshaft
replaced oil pressure pump
checked the lifters

and after all that didn’t fix the issue, they need to take the engine out and check it from the bottom and that will cost me $9000 just labor no parts

i have 2015 slk250 1.8 turbo the same engine for c250 it had 25k mileage when the issue started now it had 44k


please if anyone knows what should i do ? I spend so mush money on and nothing fixed the noise getting louder no check engine light .

Odd Piggy

Not being sarcastic. The car isn’t worth $9000. Time to trade it in or sell it and get something newer with a warranty.

mtaani

thank you for your reply we are trying to find a solution to fix our cars so many people has the same issue with their cars of course i will not pay the $9000 I just mentioned how Mercedes dealership did know how to fix the issue .
And i have mentioned what part they replaced trying to fix it but with no luck

if i wanna trade it in or sell i will not waste my time looking for a solution