350 - Problems from the bottom - Exaust + Shielding - Getting Crazy!!

Daniele · 10-13-2008

Hello.
I have an 350 and 4 days ago I brought it to the MB Garage to fix some bad work they did in the past check-up.

They unmounted completely the exhaust system,
and when they put it back on the car, screwed up something, so that the rear mufflers tips were not centered i thye compartments, and I almost got the bumper liquefied to the passenger side.

BTW, I went back to fix it and they told me they fixed it but I discover they just badly cutted the inner part of the bumper so that it would not touch it again!
That's happened on Friday night. So I got back the car and Saturday I could not call anybody to complain whe I discovered it in the morning.

Really bad work BTW!

However in this two days I tested the car for a few hundred miles and I got 2 brand NEW really weird problems!

I can't find the cause even if I spent all day today and yesterday night looking for it.

First Problem:

I start the engine (Cold)
I gently push the gas pedal till it arise 1800/2200 RPM
The car start to mutter but this is normal.

Then I have 3 cases:

1) at 1800 RPM more or less all of a sudden, a bang,
not loud,
but like a big bobble of air with a deep sound,
it bang in the exhaust conduct like something banging on some iron but not so metallic sound. It is weird to explain I know!
It sound like a gunshot but deep (musically speaking more Bass Sound)

2) while the engine COLD is in IDLE all of a sudden the same BANG...! Same Sound! I have to say it happen even at HOT engine but less as far as I can check.

3) The most weird now! I turn off the engine... the car performing the final "check up" conclude (dashboard DVD check and all the electric noises finish) and here we go.. after 5/8 seconds after I unplug the key the BANG occur again!! Even if it already occured during the run!

That's is driving me crazy!
I tested all day! I spent almost 1/4 of gasoline tank to test it. (the gasoline consumption arise 22 Liters/100Km -- 5.7US Gallons/62 Miles)

I did to find if a relation exist between different RPM standing position or Cold or Hot engine start, Various stop and go etc.
Nothing I could do to exact replicate the event in a prefect and predictable way! Let say in a scientific way.

That's driving me crazy!!

-------------------------------------------------------

Second problem:

Wile driving to 80Km/h --50mph (maybe even more I did not tested higher speed) a rattling really noisy sound come out from the central console (between the gear level and the armrest). I could not define where, since I was driving so.. to avoid a crash I could not check the exact position.

It is not so high in volume but this tickling is tedious at the point that hurt my brain while speaking with the passenger.

Once stopped I lift up the car today.
I checked this:
with the engine on IDLE from the gear level I can hear something.
I have to gently attach the ear to the Gear Lever Knob. Not pushing it or it disappear!

That's not the rattle sound I hear while driving. It is very low sound in volume.
Probably this is normal vibration from the gear lever.

Going under the car, at the exact position where is located the gear lever under the floor I could find an X where the two exhaust pipes join.
Up there you have many metallic shields, to avoid, probably, heat propagation.
Well I checked that the central one if pinched gently will sound like a rattle but I can't compare since I can't find anyone who was pinching for me wile I was inside the car. Too scary be under the car

The code on EPC of this shield is A 171 682 04 71.

So... after all this long reading...
What it can be the problem one and the problem two?

I guessed the problem ONE could be caused by:
1) Dirty Gasoline ?? It was empy and I fill it again today and same prob.
2) Air Bobble in the conduct (Is that possible??)
3) Spark Plug to be changed (Maybe they missfire - STARDAS will Report it?)
4) Air conduct with some problem (I intalled by 6 month Green Filters)
5) contaminated injectors
6) a plugged fuel filter
7) a worn fuel pump
8) A loose cam chain (older motor)?
9) Poor air flow. air filter worn?
10) A loose spark plug cable connection or a worn or damaged ignition parts?
11) Improper spark plug gap and carbon build up on one or more pistons?

The Problem 2...
1) Loose shield?
2) Gear Lever not fixed well
3) more and more...

Can you please help me out in this cases?
I'm really afraid the MB Garage will destroy my car when they have in hands it!

Thank You All..

Regards

Legin · 10-14-2008

I would say they are all related to the exhaust removal. The bang is most likely exhaust or heat shield expansion causing metal to deflect and then a bang. The only other alternative is the exhaust now has a joint leak allowing 02 in the exhaust and exploding internally in contact with unburnt hydrocarbons.
Get the exhaust refitted properly.
And I thought UK Merc dealers were crap !

DansSlk · 10-14-2008

I'm inclined to go along with this diagnosis, a lot of things change in that pipe as the car warms up and then cools down.

It could be shifting about all over the shop under there.

The only thing that does confuse me is you mention a bang when you remove the key, if you leave the key in for say 1 minute does the bang happen with the key in? If it does then it goes along with the exhaust but if the bang depends on you removing the key its something else.

**UK-C200** · 10-14-2008

Hmmm - is the "bang" after removing the key like a backfire (explosion?) or a mechanical sound?

DansSlk · 10-14-2008

Quote:

Originally Posted by UK-C200

Hmmm - is the "bang" after removing the key like a backfire (explosion?) or a mechanical sound?

Steeting lock right?

Same train of thought mate

Daniele · 10-14-2008

Quote:

Originally Posted by DansSlk

I'm inclined to go along with this diagnosis, a lot of things change in that pipe as the car warms up and then cools down.

It could be shifting about all over the shop under there.

The only thing that does confuse me is you mention a bang when you remove the key, if you leave the key in for say 1 minute does the bang happen with the key in? If it does then it goes along with the exhaust but if the bang depends on you removing the key its something else.

I went to the MB garage they (The Chief) did "run around" the car for 1 hour or two.. results....
Nothing to say!
They don't know.
I have a video were you can clearly hear 3 BANG in less the 1 minute and 1 BANG after I turned off the car.
Immediately after I switched off the car.
This after I ran the car for 9 minutes at +/- 2.000 RPM

Does anyone know a prog to delete the unwanted part of the MP4 file so I can show you the BANGS?

Daniele · 10-14-2008

Quote:

Originally Posted by UK-C200

Hmmm - is the "bang" after removing the key like a backfire (explosion?) or a mechanical sound?

Sort of explosion not mechanical I guess

Daniele · 10-14-2008

Quote:

Originally Posted by DansSlk

Steeting lock right?

Same train of thought mate

Not only when I remove or put the key in Off Position without removing it from the dashboard. Even when the car is running.

Daniele · 10-14-2008

BTW today I discovered that during the MB regular check A-B-C etc.. no one changed the Park Plugs! I have the same Spark Plug from 60.000 Km more or less!!
I think it is too much don't you think?
I ordered today "Bosh Super 4" I read they are better then NTP.

What do you think?

mtiede · 10-15-2008

I think the plugs are supposed to be good for 100,000 miles so that SHOULDN'T be the problem, but sounds like a relatively easy thing to try. I'm wondering if a valve is sticking open...

Daniele · 10-15-2008

I have just add to the gasoline a solvent to clean the injectors and valves
I hope this will help to find the problem.

DansSlk · 10-15-2008

I'm sorry just to help me clarify - could you tell me do any of these banging noises happen with the engine off?

Daniele · 10-16-2008

Quote:

Originally Posted by DansSlk

I'm sorry just to help me clarify - could you tell me do any of these banging noises happen with the engine off?

Yes.
After I turn the key off as soon as I turn the engine of it happend one time to hear te bang and other times after 4/5 seconds with the engine turned off

mtiede · 10-16-2008

Okay, no sticking valve

DansSlk · 10-16-2008

Quote:

Originally Posted by mtiede

Okay, no sticking valve

Exactly and its not a problem with the injectors, fuel or spark plugs either.

DansSlk · 10-16-2008

Quote:

Originally Posted by Daniele

Yes.
After I turn the key off as soon as I turn the engine of it happend one time to hear te bang and other times after 4/5 seconds with the engine turned off

It really sounds like the exhaust

mtiede · 10-16-2008

Yeah, maybe something heating up and expanding and it isn't WELDED so it moves and pops?

What the heck were they doing anyway?

10-13-2008	#1 (permalink)
Daniele SLK World Member Join Date: Jan 2008 Location: Italy Vehicle: SLK 350 + AMG Kit Posts: 97 Country: Thanks: 0 Thanked 6 Times in 3 Posts	350 - Problems from the bottom - Exaust + Shielding - Getting Crazy!! Hello. I have an 350 and 4 days ago I brought it to the MB Garage to fix some bad work they did in the past check-up. They unmounted completely the exhaust system, and when they put it back on the car, screwed up something, so that the rear mufflers tips were not centered i thye compartments, and I almost got the bumper liquefied to the passenger side. BTW, I went back to fix it and they told me they fixed it but I discover they just badly cutted the inner part of the bumper so that it would not touch it again! That's happened on Friday night. So I got back the car and Saturday I could not call anybody to complain whe I discovered it in the morning. Really bad work BTW! However in this two days I tested the car for a few hundred miles and I got 2 brand NEW really weird problems! I can't find the cause even if I spent all day today and yesterday night looking for it. First Problem: I start the engine (Cold) I gently push the gas pedal till it arise 1800/2200 RPM The car start to mutter but this is normal. Then I have 3 cases: 1) at 1800 RPM more or less all of a sudden, a bang, not loud, but like a big bobble of air with a deep sound, it bang in the exhaust conduct like something banging on some iron but not so metallic sound. It is weird to explain I know! It sound like a gunshot but deep (musically speaking more Bass Sound) 2) while the engine COLD is in IDLE all of a sudden the same BANG...! Same Sound! I have to say it happen even at HOT engine but less as far as I can check. 3) The most weird now! I turn off the engine... the car performing the final "check up" conclude (dashboard DVD check and all the electric noises finish) and here we go.. after 5/8 seconds after I unplug the key the BANG occur again!! Even if it already occured during the run! That's is driving me crazy! I tested all day! I spent almost 1/4 of gasoline tank to test it. (the gasoline consumption arise 22 Liters/100Km -- 5.7US Gallons/62 Miles) I did to find if a relation exist between different RPM standing position or Cold or Hot engine start, Various stop and go etc. Nothing I could do to exact replicate the event in a prefect and predictable way! Let say in a scientific way. That's driving me crazy!! ------------------------------------------------------- Second problem: Wile driving to 80Km/h --50mph (maybe even more I did not tested higher speed) a rattling really noisy sound come out from the central console (between the gear level and the armrest). I could not define where, since I was driving so.. to avoid a crash I could not check the exact position. It is not so high in volume but this tickling is tedious at the point that hurt my brain while speaking with the passenger. Once stopped I lift up the car today. I checked this: with the engine on IDLE from the gear level I can hear something. I have to gently attach the ear to the Gear Lever Knob. Not pushing it or it disappear! That's not the rattle sound I hear while driving. It is very low sound in volume. Probably this is normal vibration from the gear lever. Going under the car, at the exact position where is located the gear lever under the floor I could find an X where the two exhaust pipes join. Up there you have many metallic shields, to avoid, probably, heat propagation. Well I checked that the central one if pinched gently will sound like a rattle but I can't compare since I can't find anyone who was pinching for me wile I was inside the car. Too scary be under the car The code on EPC of this shield is A 171 682 04 71. So... after all this long reading... What it can be the problem one and the problem two? I guessed the problem ONE could be caused by: 1) Dirty Gasoline ?? It was empy and I fill it again today and same prob. 2) Air Bobble in the conduct (Is that possible??) 3) Spark Plug to be changed (Maybe they missfire - STARDAS will Report it?) 4) Air conduct with some problem (I intalled by 6 month Green Filters) 5) contaminated injectors 6) a plugged fuel filter 7) a worn fuel pump 8) A loose cam chain (older motor)? 9) Poor air flow. air filter worn? 10) A loose spark plug cable connection or a worn or damaged ignition parts? 11) Improper spark plug gap and carbon build up on one or more pistons? The Problem 2... 1) Loose shield? 2) Gear Lever not fixed well 3) more and more... Can you please help me out in this cases? I'm really afraid the MB Garage will destroy my car when they have in hands it! Thank You All.. Regards

10-14-2008	#3 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,752 Country: Thanks: 96 Thanked 221 Times in 173 Posts	I'm inclined to go along with this diagnosis, a lot of things change in that pipe as the car warms up and then cools down. It could be shifting about all over the shop under there. The only thing that does confuse me is you mention a bang when you remove the key, if you leave the key in for say 1 minute does the bang happen with the key in? If it does then it goes along with the exhaust but if the bang depends on you removing the key its something else. __________________ One thing you will learn with German cars - If it's simple it ain't happening.

10-15-2008	#12 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,752 Country: Thanks: 96 Thanked 221 Times in 173 Posts	I'm sorry just to help me clarify - could you tell me do any of these banging noises happen with the engine off? __________________ One thing you will learn with German cars - If it's simple it ain't happening.

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10-14-2008	#2 (permalink)
Legin SLK World Member Join Date: Jul 2008 Vehicle: SLK55AMG Posts: 39 Country: Thanks: 1 Thanked 2 Times in 2 Posts	I would say they are all related to the exhaust removal. The bang is most likely exhaust or heat shield expansion causing metal to deflect and then a bang. The only other alternative is the exhaust now has a joint leak allowing 02 in the exhaust and exploding internally in contact with unburnt hydrocarbons. Get the exhaust refitted properly. And I thought UK Merc dealers were crap !

10-14-2008	#4 (permalink)
UK-C200 Elite SLK World Member Join Date: May 2008 Location: London, UK & Baton Rouge, Louisiana Vehicle: 04 RHD C200K Coupe, 06 LHD SLK-350 Other Toys: Nacra F18 Posts: 578 Country: Thanks: 38 Thanked 124 Times in 78 Posts	Hmmm - is the "bang" after removing the key like a backfire (explosion?) or a mechanical sound?

10-14-2008	#9 (permalink)
Daniele SLK World Member Join Date: Jan 2008 Location: Italy Vehicle: SLK 350 + AMG Kit Posts: 97 Country: Thanks: 0 Thanked 6 Times in 3 Posts	BTW today I discovered that during the MB regular check A-B-C etc.. no one changed the Park Plugs! I have the same Spark Plug from 60.000 Km more or less!! I think it is too much don't you think? I ordered today "Bosh Super 4" I read they are better then NTP. What do you think?

10-15-2008	#10 (permalink)
mtiede Founding Member #7 Join Date: Jun 2006 Location: Western New York Vehicle: 2006 SLK 350 Posts: 1,642 Thanks: 100 Thanked 55 Times in 45 Posts	I think the plugs are supposed to be good for 100,000 miles so that SHOULDN'T be the problem, but sounds like a relatively easy thing to try. I'm wondering if a valve is sticking open...

10-15-2008	#11 (permalink)
Daniele SLK World Member Join Date: Jan 2008 Location: Italy Vehicle: SLK 350 + AMG Kit Posts: 97 Country: Thanks: 0 Thanked 6 Times in 3 Posts	I have just add to the gasoline a solvent to clean the injectors and valves I hope this will help to find the problem.

10-16-2008	#14 (permalink)
mtiede Founding Member #7 Join Date: Jun 2006 Location: Western New York Vehicle: 2006 SLK 350 Posts: 1,642 Thanks: 100 Thanked 55 Times in 45 Posts	Okay, no sticking valve

10-16-2008	#17 (permalink)
mtiede Founding Member #7 Join Date: Jun 2006 Location: Western New York Vehicle: 2006 SLK 350 Posts: 1,642 Thanks: 100 Thanked 55 Times in 45 Posts	Yeah, maybe something heating up and expanding and it isn't WELDED so it moves and pops? What the heck were they doing anyway?

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