rubycon65

I need some advice.

1. After a regular service routine on the GL450, the local MB dealer noticed that the car was running rough and recommended replacing the spark plugs (the car has 80K miles).
2. That didn't resolve the issue and after that, they recommended changing the timing chain tensioners.
3. That didn't resolve the problem and during that work, they discovered that they needed to reseal the upper front timing cover.
4. After that they found that the center valves for the cam shafts are leaking and replaced those.
5. After that they run into some code issues and changed the cam shaft (they didn't charge me for that, which makes me suspicions that something went really wrong with the car.)
6. I still have the rough/rattling problem and now they recommend to change the oil pump at the cost of $3,500 (this seems high to me)
7. So far I have $6,500 on this repair and if I add the oil pump i reach $10K for a running rough/rattling problem.

Does this seems like a typical issue for the 2015 GL450 with 80K? Any advice is more than welcomed here.

arsupisemnet

How about compression test and cylinder scope? Shady dealership riping you apart.

ChrisHimself

i have no input for this but good god is the dealer incompetent

i guarantee you 2-3-4 were completely not necessary and were a result of them rooting around where they shouldn't and overdiagnosing based on wet spots that they caused.

they LOVE to sell that timing chain tensioner update because there are like 7 revisions to them which don't actually fix or improve anything on the GL and GLS, it pays huge, and you access them through the timing access port in the upper cover which hilariously started leaking after they fiddled with it. My actual advice is to cut your dealer off and find a good independent who actually uses things like a stethoscope, his eyes, and ears. I think the service advisor is telling the technician what to find at this point. If an oil pump is failing on a car at this age I would never ever buy a Mercedes again. They want you to buy a new oil pump without metal in the oil, proof of where the noise is coming from, or test driving the car?

Do me a favor and dipstick your car, make sure the oil level isn't overfilled and your car isn't breathing oil through excessive crankcase pressure? Cars too new to have actual parts breakages that they're describing and the GL isn't exactly a racecar that is super hard on parts. I'm sorry I don't have actual advice we're so far down the rabbithole I have no idea what it could actually be after these people have ravaged your vehicle. 10k buys you maintenance for 10 years normally.

silvergl

I agree w the above. But you provided limited info on rough running. I would definitely get the cylinders scoped. It could be bore scoring. Easy to do, start with #5, it usually goes first.

Get a good independent.

rubycon65

To clarify running rough - the car had an ocasional rattle to the point of shaking when I cold started the car. It didnt happen all the time. After like 10-20 seconds the car was running fine. Sometime at 80-90 mph I will hear a wibrating sound, but I don't know if that is related to the cold start issue.

rubycon65

After many months and parts, the car is still not fixed. Here is the noise the car makes for 10-15 seconds when it starts cold or after 1-2 hours sitting. Also, sometimes the car is shaking badly when making this noise.
Any ideas are more than welcome.

GL450 Rattling Noise

mcoady1

Dealers love that reseal job on the cylinder head job. My recent nonconsensual stealership visit resulted in the same recommendation on a GLS with the same engine despite my mechanic inspecting it a few weeks before. On this forum the only users finding this issue and recommending repairs seems to be ones who recently visited a dealer.....

silvergl

Seriously stop throwing parts at it and get the cylinders scoped.

Gray_Panther

M276 bi-turbo V6 has cylinder scoring issues like the M278 V8?!

what gas have you been running?

rubycon65

@Gray_Panther - only premium gas

lexnoir

That sounds horrible. I can't believe they couldn't diagnose that. That's a lot of money being spent to come out with the same issue. When you said vibrating noise I was thinking of something more subtle. Not sure if it's the video or not but I hear banging not vibration. I agree with other posts on the scoring issue. It's a common issue with this engine.

mcoady1

Correct me if I'm wrong: scoring only an issue with M278.

Has this been a similar widespread issue with M276's?

lexnoir

You're right the scoring is an M278 issue.

arsupisemnet

People with strange logic. Scoring issue in any turbo engine with Alusil..... Either be Audi, or VW, or BMW, or MB.... It just normal way off being.
Old naturally aspired do suffer to some extend, just not that progressive...

rubycon65

@arsupisemnet - are you saying that scoring issues are typical for these engines? I was hoping to get more than 80K from an MB engine; however, here is a statement from another forum which makes me feel that I was too optimistic

"The M278 engine has problems with the cylinder (coating). I recently took two M278 engines apart. All cylinders of both engines had a similar damage. Both cars had around 100k miles. Both engines did still run but were about to seize up. The cylinders and pistons get scratched. The two theories are that it is either caused by carbon deposits or by faulty injectors. I noticed in both cars excessive junk build up on the valves. This can get into the cylinders and damage them. According to the injector theory the injector drips/injects too much/at the wrong time fuel. The gas washes away the oil film on the cylinders, creating excessive friction.

The M278 engine is highly flawed in my opinion and many of them will suffer destruction between 100k and 150k miles. I think I read about engines that don't have that problem. I am not sure what causes these issues, I think for some reason they gum up internally and also the injectors will cause damage."

BTW - The VIN decoders tell me that I have a M276 V6-GASOLINE ENGINE M276

arsupisemnet

That is an opinion of so called "engine assembler". Me is "engine builder". The damage is well known to German car community, started many years ago with Porsche, even they have different block technology. Engine block damage begins ones piston coating gone, you like it or not. Statistically on average it starts at 75k miles... Now the "opinion" he has related to all modern direct injection engines - the gunk on valves are carbon and other deposits from engine's operation, which used to be washed away in regular car through intake by fuel injected in or supplied through carburetor. Has nothing to go with engine longevity. It only affect valve sealing capacity in the case of extreme buildup.
Leaky injectors is another myth, ECU system controls injectors very precisely with very big accuracy - just because of the progress, and that is the reason you don't feel gasoline smell or detonation anymore. If there is leaky injector washing away oil film - your engine will last may be 20-30k miles - i just know it from bad tuning of performance LS where ECU badly handle performance camshafts causing extremely rich idle.
In your case - if you have 8 cylinders - you have M278.

rubycon65

The VIN decoders tell me that I have a M276 V6-GASOLINE ENGINE M276 in my 2015 GL450

BlownV8

2015 GL450 is a V6. 2013 - 2014 had the V8.

arsupisemnet

Well, lucky you, your engine is not pushed to it's limits, so you can keep driving it much longer...

Gray_Panther

Waiting on cold start video from OP so we can see if shaking goes away after 20s or and to hear and see the shaking.
Need more info to diagnose from our chairs.

ygstraps

If it's over 80,000 miles, you can look to see if it's the camshaft adjuster, usually there's a noise and sometimes a vibration on a cold start, and it's a good idea to diagnose if the angle of the left and right intake camshaft solenoid valves are within the standard range of values (31-46°), and it's usually the right intake camshaft adjuster that has the highest probability of being faulty.

mblover2023

I own a 2014 Mercedes-Benz GL450. When I start the engine, I hear a knocking sound that becomes more pronounced when I accelerate. However, the noise significantly diminishes when I reach speeds exceeding 40 miles per hour. Interestingly, there is no noise when I have the air conditioning (AC) turned on, this is for last 5 months, i am still driving

CaliBenzDriver

> You should OPEN A NEW THREAD - You issue likely related to loose serpentine belt caused by worned out tensioner.

> This thread is limited to an extreme case of startup rattle associated with failed VVT Phasers. It causes noise for 1mn then goes away with live oil pressure.

++++++++++
> For M276/8 owners: beware of the excellent Bosch ECU managing your oil pump to save fuel.

It does that with a solenoid to command low oil pressure when driving below 3,500.RPM...
That means piston squirters are mostly deactivated below 20PSI! 🫤

Hence some chaos *may* result :

• heat stressed pistons cracks,
• scored dry cylinder walls,
• leaking chain tensioners,
• knocking VVT worned pins,
• dry shaved camshafts,
• seized HPFP dry pistons,
• vaporized oil coating valves, 02, cats,
• burned CPS feeding oil-in-harness...

> Firmware Bug:
There's an experimental procedure undergoing road tests. It has to do with limiting pump solenoid activity.

OEM repair is a cheap firmware flash, not yet available.
This troublesome feature can be blamed on summer interns.

Low pressure should be limited to 750.RPM idle only not highway speeds below 3500.RPM.

-- Managed On/Off based on clever map calculations of engine load vs. temperature.
Open loop control without any feedback sensor to measure actual pressure leads to a crude basic On/Off:
= PREMATURELY WASTED ENGINES.

Is it beneficial to save gas and burn engine oil instead ??


Courtesy of Master @S-Prihadi in-depth research.

arsupisemnet

Some bs, squirters are designed for cooling at extreme loads.
Most of mentioned symptoms are due to different reasons.

CaliBenzDriver

arsupisemnet:
Can you shine some light with your engine builder expertise, yes?

What happen to M276/8 engines when driven at highway speed with limited oil pressure?


Do piston squirters shut off below 20Psi with individual ball-on-spring valve?


How do squirters only "cool extreme loads" - Normal loads no need oiling ?


You say failures "symptoms are caused by other reasons" - Like what other reasons you know cause these symptoms ??


Do you think normal oil pressure can help restore normal wear schedule?


Do you think it is beneficial to drive on low-oil pressure??


Why is so much burning oil getting vaporized through the intake ?