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After it starts up, the noise will disappear. The car drives fine and I don't feel any hesitation, no rough starts or rough idling. It drives just just fine. I also have a corresponding P0016 Crankshaft position - Camshaft position correlation CEL (pulled with ODBII MX+ reader). After the engine is warm, if I was to shut off the engine and start it back up, the rattle is not there. Only after the vehicle has sat for a while. Similar to what others have reported in this forum.
I've taken it to an indy shop and the MB dealership. Indy shop said it's probably the camshaft adjuster magnetic but wanted about $400 to diagnose, first by changing the position of the magnet (left to right and vice versa), presumably to see if the corresponding CEL will be thrown when the bad magnet is switched. If that's the case, worst case they said is to replace the camshaft adjuster magnets and labor totaling another $1000. Of course, that's if the issue is the magnet and only the magnet.
I then took it to the MB dealership to get another look. They charged me $200 for the diagnoses and wrote the following: "Found there was an issue internally in the cylinder head, adjuster is broken and the intake camshaft on Bank 1 is making noise. Estimate of $10,000 if cylinder head, camshaft and adjuster are needed. Further diag would be needed to tear down head to evaluate."
Needless to say, I did not give them the go ahead to fix it. I've been scouring the forum to see what I can understand about this cold start rattle and the P0016 issue. There's much discussion on the potential cold start rattle issue but not much on the P0016 CEL (except for this one thread - https://mbworld.org/forums/c-class-w...ml#post8190092).
So my questions:
1) Should I be taking the MB dealership's word at face value or be skeptical of it? The SA mentioned there maybe an issue with the lifter which eventually can cause the valve to do something to the piston. I didn't get all the details since my head was just fixated on the potential $10k repair cost. I may want to call them back.
2) If the rattle is happening only on cold start up but not when the engine is warm, could this be an oil viscosity / oil filter issue? I've read that can potentially cause issue if the oil isn't getting to where it needs to be thus causing the rattle. The MB SA also mentioned the same thing. I had the 70k service done (oil / engine filter / cabin filter / spark plugs) when I took the car into the Indy shop.
3) What's the chance of this being just the magnet issues or could it be more and thus much more expensive fix?
4) What's the chance of this detonating the engine soon? Or should I be seeing a gradual decline and increasing number of issues cropping up over time (rough start, rough idle, hesitation, etc)?
If it's going to be at the $5k+ range, I may just trade it in for another vehicle. It sucks as this car has been pretty much trouble free EXCEPT for this huge issue. Any advice would be greatly appreciated!
10K seems excessive, the cylinder head is never damaged on the ones I've seen, the gears are a fairly common failure. The gears are supposed to lock into a base position when the oil pressure drops, the locking pin breaks, so they slap back and forth on startup until oil pressure builds, and set the cam position codes. Once the oil pressure comes up and the solenoid can control the position, they stop rattling. So I'd be inclined to believe you need a gear, if you do one, do both, and probably the chain as well at this age, as they did seem to stretch pretty commonly on the 271, not sure on the 274 as I wasn't there long enough to see many high mileage ones, I've been gone from MB for over 2 years now.
I have m274 engine 2017 GLC300. From 125,000km odo, I heard only 1 second cold start rattling. Now at 132,000 km odo, I heard 3~4 seconds rattling with P0016 code at cold start.
I searched all the YouTube and web, I concluded the fail must be the intake cam adjuster ( variable valve timing gear) inside pin, worn out. Common problem of many mercedes engines.
Magnetic part should be okay because the engine works normally after the noisy starting. Also warm starting is normal.
Cam position sensor, cam adjuster solenoid also should be okay I think.
Oil type and oil filter not matter.
They replace both intake and exhaust cam adjusters at the same time.
2 parts cost is $2,000+ for MB oem, $1,000 at Rockauto, $200 at Amazon or AliExpress. I ordered $200 parts also ordered the cam shaft timing holding down special tool for about $100. I will replace them myself next week once parts are delivered.
If you bring these parts to an indy shop, they sould replace them in two~three hours.
Part numbers, latest improved, for my m274 engine are;
A2700506100 intake cam adjuster
A2700506200 exhaust cam adjuster
But your m276 engine needs the different part numbers.
Special tool (Engine Timing Tool KIT M133 M270 M274 for Benz Mercedes):
ItalianJoe1, thanks for your input.
sn202020, thanks for the info and those videos.
From all the reading about prior engines (M271 to M274) it sounds like a common MB engine issue with the pin and affecting the adjusters. I wish I can even tear down the engine to try to figure things out as I love a good challenge, however I've never done engine work (plenty of suspension and exhaust work), it's my wife's only car and it'll take me a while to figure things out.
I may take it to another indy shop with this info and see what they say and what they can price out.
I did take it to a Kia dealership (looking at a Telluride) to see what they may offer for trade in. Told them of the CEL and was asked what I know of the rattling noise. I told them the one shop told me it's probably the camshaft sensor. Even with this knowledge, they said they can potentially offer $23k on a trade, but may lower the offer if the shop mechanics determines more work is needed. Even if I can get $20k or close out of it, it maybe worth it.
I have m274 engine 2017 GLC300. From 125,000km odo, I heard only 1 second cold start rattling. Now at 132,000 km odo, I heard 3~4 seconds rattling with P0016 code at cold start.
So you have been able to drive your vehicle without too much of an issue during this time? Do you not have concerns that the car's engine would bust a valve or destroy the engine which would then cost more to repair? Or would that not likely to happen?
Your current experience is what's happening to my car now.
So you have been able to drive your vehicle without too much of an issue during this time? Do you not have concerns that the car's engine would bust a valve or destroy the engine which would then cost more to repair? Or would that not likely to happen?
Your current experience is what's happening to my car now.
Yes, I concern when I start the engine for 3~4 seconds with rattling noise at cold(or after engine off more than 30 minutes)
But once the engine started, all looks normal. then I erase the P0016 code.
Restart the engine right after erasing the code is just less than 1 second WITHOUT the noise and the code.
I checked the live engine variable timing advance with my OBD tool.
RPM increasing/decreasing (700~2500 rpm) makes the timing advance degree(7 degree ~ 25 degree) relatively well, I guess.
And I never see P0016 code triggered during driving. So whenever the oil pressure is built to the cam adjuster solenoid, it works okay.
Probably worst thing can happen can be the engine not starting with multiple starting tries.
My cam adjuster parts come tomorrow. I will replace and see.
Yes, I concern when I start the engine for 3~4 seconds with rattling noise at cold(or after engine off more than 30 minutes)
But once the engine started, all looks normal. then I erase the P0016 code.
Restart the engine right after erasing the code is just less than 1 second WITHOUT the noise and the code.
I checked the live engine variable timing advance with my OBD tool.
RPM increasing/decreasing (700~2500 rpm) makes the timing advance degree(7 degree ~ 25 degree) relatively well, I guess.
And I never see P0016 code triggered during driving. So whenever the oil pressure is built to the cam adjuster solenoid, it works okay.
Probably worst thing can happen can be the engine not starting with multiple starting tries.
My cam adjuster parts come tomorrow. I will replace and see.
I'll have to do the same thing to see if the P0016 code only triggers when starting and not while driving.
I'll also check the timing degree across the rpm range as well.
Hope your replacement effort goes well and if you won't mind keeping me up to date, it would be appreciated.
I'll have to do the same thing to see if the P0016 code only triggers when starting and not while driving.
I'll also check the timing degree across the rpm range as well.
Hope your replacement effort goes well and if you won't mind keeping me up to date, it would be appreciated.
I replaced (m274 engine, 132k km odo) the cam adjusters for both intake & exhaust. Took many hours. But problem has been finally solved.
I opened old adjusters and found the typical worn out around the back plate pin hole on both adjusters.
tensioner, chain, guide, magnet, sensor are all good. Only the adjusters got the problem. Cam adjuster replacing. M274 engine
Intake cam adjuster inside. Worn out pin hole side
Exhaust cam adjuster inside
Removing chain tensioner cap (metal cap with small hidden hole in the middle. Silicone glued cap) was very hard job took me 2+ hours because I did not remove the water pump above it and not enough space to pry out the cap. So I recommend you better try to remove/install the cam adjusters without the tensioner removed. Tensioner cap. Pryed out thru center hole.
Tensioner cap removed
Tensioner and metal cap
Cap center hole was covered with tape and silicon rtv. Then installed back. And added some more silicone around.
Green coolant gasket was so flat. I wish i added some silicon under the gasket to raise the gasket height but i forgot to do. Or prepare new gasket.
Thanks @sn202020 ! What you've done is way beyond my mechanical abilities and the time it'll take me to work on. Glad to hear you got it resolved though!
So you're saying the issue was the worn out back plate pin hole for both intake and exhaust adjuster? Did you just replace the back plate and pins or the whole camshaft adjusters for both intake/exhaust? After the fix, did the rattle on cold startup no longer present itself?
Thanks again for the information. The first indy shop wanted to switch the camshaft adjuster magnets first and then see if it's the magnets or not. I'm afraid they don't know what they're looking for and will be spending a lot of time/money trying to diagnose the problem by taking the engine apart and testing various pieces and replacing. At least with your findings and with a shop that may have more experience with these issues, I can show them your finding.
Thanks @sn202020 ! What you've done is way beyond my mechanical abilities and the time it'll take me to work on. Glad to hear you got it resolved though!
So you're saying the issue was the worn out back plate pin hole for both intake and exhaust adjuster? Did you just replace the back plate and pins or the whole camshaft adjusters for both intake/exhaust? After the fix, did the rattle on cold startup no longer present itself?
Thanks again for the information. The first indy shop wanted to switch the camshaft adjuster magnets first and then see if it's the magnets or not. I'm afraid they don't know what they're looking for and will be spending a lot of time/money trying to diagnose the problem by taking the engine apart and testing various pieces and replacing. At least with your findings and with a shop that may have more experience with these issues, I can show them your finding.
Both adjusters were replaced. I couldn't find the back plate seller for my adjusters. And adjuster price was cheap anyway from AliExpress.
Cold start rattle is gone. Never heard anymore.
Forget about adjuster magnet switching. Just replace all 4 adjusters. Your engine m276 has 4 adjusters. I searched and I believe these parts are for your m276 v6 engine.
All 4 adjusters priced only about US$550 (=C$692) includes shipping from AliE.
M276/278/157 Timing Tool is US$80, if your individual shop doesn't have this tool you better buy it to hold the crankshaft during removing the adjusters..
Both adjusters were replaced. I couldn't find the back plate seller for my adjusters. And adjuster price was cheap anyway from AliExpress.
Cold start rattle is gone. Never heard anymore.
Forget about adjuster magnet switching. Just replace all 4 adjusters. Your engine m276 has 4 adjusters. I searched and I believe these parts are for your m276 v6 engine.
All 4 adjusters priced only about US$550 (=C$692) includes shipping from AliE.
M276/278/157 Timing Tool is US$80, if your individual shop doesn't have this tool you better buy it to hold the crankshaft during removing the adjusters..
thanks for the info @sn202020 . I've taken it to a local indy euro shop and describing some of the symptoms and said they've dealt with these issues before. I'll probably get a good breakdown on estimate on Monday. Wish I had the time and additional vehicle so I can attempt to work on it.
thanks for the info @sn202020 . I've taken it to a local indy euro shop and describing some of the symptoms and said they've dealt with these issues before. I'll probably get a good breakdown on estimate on Monday. Wish I had the time and additional vehicle so I can attempt to work on it.
If I were you, i will order parts and receive them. Then bring the adjusters and ask to replace by showing youtube at a couple of indi shops. For $1,000 labor or so.
I listened to your noise vid. Try switching to 5/40 oil if you dont already have that. This noise is a tentioner of some kind. There's a you Tube on the 2.0 liter motor tentioners about how the stepper "teeth" are ground away so chain doesnt stay locked when shut off. The motor is out of the car and the tech seems like he knows what's happening. He has the problem in his hand in my opinion. (My wifes car does the exact same thing. I told her to go back to a CTS)
08-02-2021, 12:14 AM
