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1999 ML320
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453 Posts
Discussion Starter #1
Hi to all, for a change, I am in need and would like to get some help too!
It is getting cold here in Chicagoland and for two weeks I noticed rattling noise when bringing my ML to a complete stop, starts at about 10 mph to zero or between 1000 to 700 RPM idle only when car is warmed up. With cold engine the noise is not there and I can't duplicate it but ones warmed up, even with selector in park, when I rev the rpm and the engine speed is comming down, clicking, ticking rattling noise comes on.
I would say that it is sound like it is comming from left side of the engine and I installed new serpentine belt tensioner thinking at 174K the bearing is pretty much done. The bearing in the pulley is bad but this did not take care of my problem. Thought about hydraulic valve lifters but I only made 4K miles on new 0W40 oil and filter. I went under and tried to hit cat convertors but they seems to be solid (when they are cold without any rattle noise).
I didn't check the bearing on power steering pulley when I had the belt loose and I have about 34K miles on new harmonic balancer, water pump and transmission. I was thinking PS pump or my timing chain tensioner but I wish it is just the exhaust.
Any hint or help would be greatly appreciated!
Happy Holidays to all of you and yours!
Bernard
 

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'01-E320 & 02-ST2
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I have the same noise...its coming from my cats. Ive just been living with it, cats are expensive.
That was going to be my suggestion, too. However, since he's not in CA he can get an aftermarket cat installed pretty cheaply.

OP that is what I'd do were I you. Take it to an exhaust shop, it's probably the front one. Couple hundred bucks, you're all set. Let it go long enough and you may damage the other one or clog everything up, then you'll have bigger problems.

Good luck.
 

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1999 ML320
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453 Posts
Discussion Starter #4
Thanks guys, I was carefully listening to it on the way home and the quicker stop I make the less noise will come out and it's not always there, I made few stops without noticing anything. I'm already happy that this is just a converter.
I know they don't have any cracks in them because couple months ago I replaced both front oxygen sensors. Car is driving fine and quiet even under hevy load.
I used to get multiple misfires with old sensors whenever I would take it above 4000 rpm now, coulpe of time I hit 5500 or 6000 mark without cel but those couple times could of have negative impact on those converters.
I will check it one more time at full operating temperature with my welding gloves on.
In the past, I used Velasquez and sons shop for exhaust work on my old W126 (no converters there because it was euro model gray market car). First I had Midas manager to bent metric pipes to my plywood drawing for $40, then I had the mexican guys weld them in for me for $60. I sold my mig to my budy in Atlanta, otherwise I would of done the job on my own.
I very much appreciate your time and help.
Bernard
 

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99 ML430, 00 ML320, 05 E500 4matic Wagon
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22,145 Posts
They may no make noise by just grabbing them and shaking them.
Gently tap them with a rubber mallet and if you hear any rattling the
screens are coming apart in the cat.
If you need a cat I am sure the exhaust shop you know can do a fine job replacing just the cat.
The damn torsion bar may be in the way if they have to take the whole pipe out to work on it.
 

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1999 ML320 and 2009 E350
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98 Posts
They may no make noise by just grabbing them and shaking them.
Gently tap them with a rubber mallet and if you hear any rattling the
screens are coming apart in the cat.
If you need a cat I am sure the exhaust shop you know can do a fine job replacing just the cat.
The damn torsion bar may be in the way if they have to take the whole pipe out to work on it.
I have the same problem and fixed by replacing the driver side cat. According to my mechanic it’s a common problem with ml320’s.
 

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Any luck with fixing it? I know the post is old but i have the same issue and need some guidance. Any imput will be greatly appreciated. Thank you.
 

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I have read all the posts where eleventh thing is pointing towards catalytic converter. But I wanted to know if @mbenz80 actually fixed it and if indeed that was the problem. Thanx
 

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94 S420 RIP 2/8/13 02 ML55AMG, 06 CLS55AMG, 89 Mas. 228, 84 Por. 911 Carrera, 93 Toyota t.t. Supra
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I did. I had a noise in the left cat and it did rattle while I was in motion and when I whacked it with a rubber hammer. Got my friend with a tig welder and a case of his favorite brew and we took off the old ones ( shoulda taken pics they two were a mess) and tig welded in new Flowmaster cats. End of problem. Concern is that if the pieces break off and they get stuck at the opening out to the muffler it's going to wreck your day so don't delay.
 

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Thank you for the reply . My rattle is really loud below 1000 rpm. When in motion it does not make the noise though in park reverse and drive sounds like the engine is an to blow up from the rattle/ knocking. I got under the car and hammered the driver side cat . I can hear a small vibration in it but the worst is the resonator . When I hammer this one sounds like stuff is moving around in it. But standing in front of the car the noise seems to come from the engine bottom part. Ohhh also get misfires on the whole driver side cylinders and one on the other side. Any help is appreciated. Thanks
 

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ML55 2003, ML55 2002, ML63 2007
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shopping, have your CAT & resonator fixed. You might find that the misfires disappear after the repairs. If the CAT or resonator are bad/blocked it will create misfires(besides your rattles)
 

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1999 ML320
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453 Posts
Discussion Starter #13
Shopping, art is correct. You probably have already blockage in your exhaust system and your engine is suffocating.
I did replace my left/driver side catalytic converter at that time with OEM rebuild from reputable warehouse but it last it for two years and same rattling noise is coming from it now. Warranty was only for one year and now I'm trying to live with it since the performance is still fine but I'm bothered every time I hear it. When I knock with my fist on the front left cat, it rattles like the previous original one so they probably replace only parts obviously bad and sell them again in hope they will last a year to pass warranty time.
Years ago when I tried to claim the bad cat converter recall, I was told by MB officials that my VIN was not effected or under this recall even though listed within in their TB.
 

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2005 E320 CDI, 2016 E250
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3,199 Posts
I had a rattle...it was the water pump. With the vehicle off, grab the fan and gently move it. If you have play - that is your issue. It took me two years to find it. Get it fixed immediately.
 
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