csmax

I have a 2010 GLK 350 with 25,000 miles (purchased in Feb). It is a CPO car and all mandated Mercedes maintenance has/was been performed (oil change 8,000, 18,000 and 24,000 miles). The problem or question is about a knocking/tapping sound at idle. It sounds like it is coming from the backside (maybe top) towards the firewall. Dealer says its normal(??). Any thoughts?

phil17

I had the lifter changed on my GLK when it was a week old back in 2010. It was just a loud " tick tick " sound at idle... Might want to look into that. I should note that as this car ages, the "tick" is back but not nearly as loud as it was back in 2010

rmfnla

Try listening with the hood opened.

It might just be something loose that is tapping and just needs to be reattached.

I know this sounds obvious but it's worth a look...

csmax

I have, thats how I know the area its coming from.

420tee

I love it when dealers say "it's normal." An unusual Knocking noise IS NOT normal. Reminds me of one of our service guys who told a customer that "they all smoke a little once in a while." This was a $150K research instrumeant. He didn't last long and neither should a "it's normal" dealer. Let me hear the same noise on other cars if it's normal.

MBRedux

Knocking noises, and sometimes even clatter noises, can be normal. It all depends on where they're coming from, and if they are caused by something that is either worn-out or out of adjustment. Otherwise, 0 lash valve systems can have significant tapping and still be working perfectly.

420tee

My advice would be to 1) Have the dealer, who must have several similar vehicles on his lot, show me a few others that make the same noise, 2) put it in writing that the noise is normal so when I have con rods sticking out of my oil pan I have recourse.

csmax

Took the car and dropped at the dealer yesterday. Of course when I left it it wasnt making the noise after the 25 min highway drive, so hopefully it will do it for them today. Tech and advisor both said they have never heard of any issue of this sort with a GLK. In fact they said it was one of the the least problemmatic of all the mercedes.

ble2716

I could not tell if it's normal or not.
But I can tell you that there is NO knocking noises on my 2010 GLK with over 67,000KM on it.

420tee

So what was the dealers' final determination?

csmax

It's still there..They have no clue. They heard the tapping sound as I described and they put a camera down the cylinders (supposedly there is a bullentin on scoring of cylinder walls and pistons) whicjh results in this type of noise. Cylinder walls and pistons are good. They are looking online to see if there are other cases and will continue tomorrow trying to figure it out. I've owned the car 2 mos (1,000 miles) and its been back to the dealer 3x already, not a good fealing.

dgiturbo

Someone on another forum posted a similar complaint and the dealer resolved by replacing the belt and tensioner.
Thought it was a strange fix, but it was a fix anyways.

420tee

At least they know it's a problem and are still working on it. I'd have a little talk with the "it's normal" jerk.

An old timer's trick to find engine noises is to put a long screwdiver, a metal rod, or even a length of broomstick against places you think the noise is and the other end against your ear. Move it around till you pinpoint it. Works like a stethoscope.

csmax

As of yesterday (Friday) they still don't know. They are now going thru TAC (technical assistance cases) with mercedes benz to see if they know of any similar cases.
Compression and cylinder balance are ok. I asked about the lifters being a possible cause and they said they seem good.
How far and how long should they have to find a fix and to what extent?

420tee

Sounds can be very deceiving as to where they originate. Waterpump bearings can give a definite knocking noise even though it sounds like it's coming from the wrong end. Worth a quick listen. I will admit as a retired service engineer to occasionally getting so deep in troubleshooting that I overlooked the simple and obvious. Is it plugged in? Can't see the forest for the trees.

csmax

Plugged in? do you mean the cars computer? If so, yes nothing on computer to go by.

420tee

That was just in reference to my comment about overlooking the obvious in a general situation, nothing directly aimed at your problem.

MBRedux

Let me take a wild guess here.... either the crank or cam positioning sensors are starting to wear and/or fail thus temporarily altering the timing, thus making an ignition ping (this will eventually throw a code when it completely fails) or the owner before you abused the engine, or over-revved it thus causing one or more of the valve tappets/lifters/followers to falter...

http://www.slkworld.com/ask-dansslk/...ter-noise.html ....... Look here

B16RacerN2NR

Most of the time a client/customer ask me to check out their slight "tick" it's been the purge valve...



I'm almost positive that this is what you're hearing since the sound comes and goes. That solenoid isn't always purging, therefore, you won't hear it all the time. Next time you can hear the tick, put your hand on the purge valve and see if you can feel it pulsing everytime you hear the tick...

Cylinder and valve train ticks just don't come and go... at least in my experience the don't...

MBRedux

We don't see many Benz's in our shop, (mostly high performance GT-R's, Lambo's, Porsches, Nissan's & Audi's... we're a Nismo Tuner) but the solenoid activated purge-valve is fairly low level and rapid pulsing, plus it doesn't change with engine rpm. If the bleed-down valve inside the follower/lifter is either worn or faulted, it can be intermittent.

csmax

Nope not it. Purge valve ticking normal. This is more of a knocking (metal against metal sound) and more towards the top of engine closer to firewall passenger side.

MBRedux

Then it's the follower/lifter/tappet! Have them pull the cover and switch out those faulty lifter/tappets.

csmax

Yesterday they removed top of engine pulled off camshafts and checked all lifters by pulling out one by one. The lifters were perfectly fine and the cams as well. The dealer is speaking directly with mercedes TAC engineering and following the procedures directed by them. Didn't hear any news today. The car has now been at the dealer 1 week.

MBRedux

I'm sorry to say, they did it wrong. If they didn't perform a pump-up bleed-down test on each of them, they did it wrong. There is NO WAY to tell if the hydraulic followers were defective by just looking at them. (Unless yours are not self adjusting. )

csmax

The info Im relaying is from the service manager, so not exactly sure how they performed the work. Supposedly mercedes is directly invoved and is walking them thru every step in hopes to find the cause.
Now my concern is after all this tearing apart what isnt going to be right after they put it all back together.
I purchased this car mid feburary (2 mos ago) and have driven 1,000 miles.
It is a CPO car, but they neglected to do some things that should of been done prior to certifiction. After 2 weeks of owning it they replaced front rotors and pads (they paid) as it should of been done under CPO.
Same visit they repaced belt and tensioner as they thought this knocking tapping sound was being caused by these.
Next visit was to update computer for tsb on transmission shifting (why werent any outstanding tsbs performed during CPO)??