MLBSlayer

Greetings all,

I have a new 2021 GLB 250 with the AMG night package. Love the car but it knocks like crazy when first started up. Is this normal? I've tried to reach out to my dealers service department but they won't answer the question.

TIA

Vladimir Livson

A ticking sound coming from the engine is normal when you hear it on outside of the car, at least on GLB. Most likely noise from valves. The hood does not have sound insulation blanket for whatever reason. Hard to judge on "crazy", your loud could be quite for someone else. Bring it to the dealer to listen, if you think it abnormal.

MLBSlayer

Thanks for the reply. It's not a ticking sound like valve tappets but an actual knock. It goes away after the car is warmed up. Just wondering if anyone else notices a knock.

Vladimir Livson

I remembered this morning that there was one post back awhile "Check Engine Light P219C" with engine issue. It was a faulty cylinder.

Odd Piggy

That is not normal. It could be tolerance build up that puts some reciprocating component out of spec leading to a failure to build oil pressure when cold. A trip to the dealer is in order, but they will have to let it sit overnight in the bay and have the servicing tech do the cold start. FYI-It is not uncommon for the overnight vehicles awaiting service to be parked outside. These are then started by the porters and moved to the service bays. If they do that, your complaint may be returned as NTF.

ErricATL

I think that I have the same experience with my GLB. When it starts up cold, the engine is much louder with ticking and other noises that I label as "healthy". However after about a minute, those noises quieten off and a rhythmic tapping noise persists for another several minutes then eventually quietens off. It's not a consistent tap tap tap, there is a noticeable rhythm, almost like the serpentine belt has a flat spot and you hear the tapping noise every time it completes a full rotation. The lingering noise does not sound healthy to me so I made a hi-def recording and sent it to MB service. I was told that from what they can hear, it is a normal sound that will eventually dissipate when the break in period is reached. I was not satisfied so I sent the recording to my Sales person for an opinion. She then asked her dealership manager to listen to the recording and then cold start another new GLB. They were hearing the same tapping noise that I described and declared it as a normal sound.

I have just reached 900 miles and the noise is still there but seems to dissipate quicker than when new. We shall see how this goes long term. I really feel that if this noise is really a "healthy" noise during the break in period, it is so unrefined and almost embarrassing for a Mercedes Benz. I have never heard such a noise in any of my BMWs or other brands during cold start up especially when new.

Odd Piggy

Can you post the recording that you made of the noise?

ErricATL

I had to shorten the video a bit but you should be able to hear the tapping.

Odd Piggy

That’s the strangest thing I’ve ever heard coming from under the hood. It’s not regular but it repeats consistently. Our GLB250 has about 5600 miles and it has never had a sound like that. We start our car every morning in the garage, so any unusual noise would be obvious.
2 things come to mind:
1-Have you actually examined the serpentine belt? Something that is moving across the same path repeatedly is causing that noise. It would be sort of a shame if MB would let you go with a “well, we just sell crappy vehicles” comment when a $50 belt would solve it.
2-Consider contacting Mercedes Benz Customer Satisfaction after you reach 1500 miles. Let them know that you are not comfortable with the dealer’s analysis, because if you don’t add that, they’ll just refer you back to the dealer. It would be an even bigger shame if the noise was coming from the timing chain and it ate an engine.

ErricATL

Thank you for your feedback and suggestions. I do plan to elevate this very soon. I will post an update when I know more.

Vladimir Livson

There is a similar issue thread on A class forum “A250 - noisy cold engine”. I am guessing it has similar engine. It ended up being a timing chain tensioner issue. Noise was gone after part was replaced.

ErricATL

Thank you, I will review that forum as well. You are the second person that has mentioned timing chain tensioner. I will be taking it into service soon and will post an update. I really appreciate you sharing your thoughts.

190Efan

It could be a timing chain issue. To state the obvious in order to cover all of the possibilities, make sure you're using only premium gas as all MBs run on premium gas only. Using a lower than required octane level gas can also cause such a knocking sound. I would also suggest taking your GLB to another MB dealer in your area to see what they say about this issue you're having.

ErricATL

Thank you. Yes, I always use premium gas, no exceptions. And that is a good suggestion, I think I will use an other dealer service center.

ErricATL

UPDATE: I had an appointment with a different service center from where I originally purchased my GLB. I was told that this particular center (Mercedes of Buckhead) was where MB Corporate sends all Atlanta metro customer complaints/issues for resolution. I brought the car in the day before the appointment so that it could be cold started by a technician the next day at the time of the appointment. I discussed in detail with my service advisor when the noise could be heard and shared the recording I had with the technician.

According the their findings along with communication with MB, they determined that this was a "normal" noise at start up. The also started up 2 other new GLBs and heard the same "rattle or tap" that was present on my vehicle.

So that is that. I am going to just drive the vehicle and try not to worry about it. After warm up, the car works as it should so I am going to roll with it. Here is the language on my service receipt:

CLIENT STATES IN THE MORNING AT COLD STAR UP THERE IS A ROTATIONAL CLANKING NOISE COMING FROM THE ENGINE BAY CHECK AND ADVISE Cause: NORMAL OPERATION. Correction: PERFORMED SHORT TEST, NO FAULT CODES FOUND. HIGH PRESSUREFUEL PUMP IS NORMALLY NOISY ON COLD START UP ESPECIALLY LOUDWHEN WEATHER IS COLD. NORMAL OPERATION NO FAULTS FOUND.

DanD.

When I switched to GLC from ML, and started it in the morning I thought I need new chain tensions, first 5-10 seconds Im hearing this knocking and engine sounds more like diesel not gas. Anyway, I went to the dealer and asked them to let me start a few others GLCs. The same thing. I think its like this engine build.
Not sure what causing it but it does sound strange.

190Efan

Since this is what MB has determined in their good effort to resolve your issue, I also agree that you should just drive the vehicle. The problem is now well documented so if there's an issue in the future, there's a record to go back to.

silver28

To note, I have this exact same knocking sound, and it drove me crazy. I sent it to the service advisor and sales rep, who also has a GLB and his makes the same sound. The service advisor didn't get back to me. It's not consistent either, doesn't always knock when you start up the car either.

I guess I will monitor like yourself. Thanks for this post, gives me some peace of mind!

Bolemne

My GLB 250 4matic start knocking on only 1000km. The same sound.
I left the car in service for overnight and they told me that tensioner has to be replaced.
I have to wait a week for tensioner to be delivered.
I'll back with an update after they replace tensioner.

It is very frustating to have those problems with a new car.
Generaly, athough GLB are excellent car, I am not happy with Mercedes, +5 months additional waiting for delivery, some payed options missing (after complains got money back), automatic parallel parking does not work any more (legal issues), Mercedes Me app stop to work after the last update and now tensioner failure on 1000km.

ErricATL

Sorry to hear about your experience.

I still believe that my issue is a tensioner as well but I was told by MB service in no uncertain terms that it was okay and a normal start up sound when cold. I hate the noise, it sounds like loose parts rattling around. This is my first Mercedes, I hope that this is not the start of a sad relationship. Please post an update if the new tensioner eliminates the sound.

Odd Piggy

Since you're in the "just drive it and see what happens" mode, I do have an anecdote. In the late 90s we had a Dodge Intrepid. When it was new, it had a tap-tap-tap noise coming from the engine on a cold start that sounded like someone was banging on the engine block with a hammer. It would be gone by the time the engine reached operating temperature. No amount of complaining to the dealer or to customer service got anything except, "That's break-in noise." Then at about 6000 miles, the noise abruptly stopped and never returned. The car wasn't particularly reliable, but there was never an engine problem. That car was replace with an identical one after an accident, and there was no noise ever with that one.

Bolemne

UPDATE: After 2 weeks of waiting for tensioner, they finally changed it and informed me that the problem is solved. I went to the car and... knocking was still there. After that, they checked another GLB, without my presence, and after that asked me to come again next week, as then they would have another GLB to compare with. It could be normal for that engine, they conclude in the end. I just reminded them that, 2 weeks ago, they claimed that it is not normal for a petrol engine to sound like a tractor.
Although the mechanics were very polite, that did not decrease my frustration.
I am considering returning GLB to a dealer, if that would be possible.

Bolemne

The problem is solved.
After mechanics consult with factory, they changed the spanner (I dont know proper word in english, they told me that on german). Mercedes trying to solve that issue generaly and I am asked to follow the situation.
hopefully this could help you as well.

Odd Piggy

Was the German Schlüssel? That’s usually spanner or wrench in English as you said. Did the repair documents show a part number? That may be helpful to others experiencing the problem.

Bolemne

I will have it on Monday, and share it with you.