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Registered 2001 SLK320
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371 Posts
Discussion Starter · #1 ·
Hi All,

I have been noticing an annoying and worsening rattle from the exhaust of over the past few weeks, first chance today to really get under the car to inspect. One of the transmission exhaust mounts was broken which I have temporarily fixed with a large jubilee clip. It made no difference to the rattle so I jacked up the car and firstly noticed that there was no centre rear mount at all but that didn't appear to be creating any problem.
594371


However as I was listening I could then clearly hear rattling which appears to be from the secondary cats.
Can anybody help diagnose from the video clips below please?


 

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Super Moderator (UK)
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33,370 Posts
@Dave2302 @M4rCu5 @Turdo2

One thing that I am aware of, sometimes when the cats wear the catalyst makes itself into a ball which can cause a rattle. Imagine a steel wool ball rattling around inside a tin can. The ball can get gradually smaller until, in rare cases, it wedges itself in the exhaust. Tends to be more of an issue with front cats, but same principle for rear.
 

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Premium Member 2001 SLK200K/2001 SLK320
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2,761 Posts
That's what I thought it probably was. Is it safe to drive like it until I get a new exhaust?
Now there's a multi-faceted question with different answers from all over the internet.

To me, it sounds like it's broken up inside rather than being clogged up, hence still flowing gases..


Personally I think I'd drive it as far as the exhaust shop


But wait to see what His Nibs says (y)
 

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Registered 2001 SLK320
Joined
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371 Posts
Discussion Starter · #6 ·
Now there's a multi-faceted question with different answers from all over the internet.

To me, it sounds like it's broken up inside rather than being clogged up, hence still flowing gases..


Personally I think I'd drive it as far as the exhaust shop


But wait to see what His Nibs says (y)
It is still flowing gases at present, I've just put it back in the garage and the Sun is shining!!!!!!!!!!
😩😩😩
I had been toying with the idea of fitting one of the "emotion valve" diverters like a certain V8 has fitted as I would like a little more roar at times but without a constant drone.

Now I guess I have a lot more options open to me:

Leave as is but empty the cats
Cut them out and straight pipe back to the rear box
New cat back system
Genuine MB or Sports

Need a cup of tea and something to eat while I go internet searching I suppose.

If anyone has an opinion on a good UK available system for a 320 I'd be interested to hear your thoughts.
 

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Registered 2000 SLK320
Joined
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89 Posts
It is still flowing gases at present, I've just put it back in the garage and the Sun is shining!!!!!!!!!!
😩😩😩
I had been toying with the idea of fitting one of the "emotion valve" diverters like a certain V8 has fitted as I would like a little more roar at times but without a constant drone.

Now I guess I have a lot more options open to me:

Leave as is but empty the cats
Cut them out and straight pipe back to the rear box
New cat back system
Genuine MB or Sports

Need a cup of tea and something to eat while I go internet searching I suppose.

If anyone has an opinion on a good UK available system for a 320 I'd be interested to hear your thoughts.
Hi Jason i've got 2 x 320s one with the cats gutted and left in situ this made it slightly noisier but not OTT the second is de-catted running a stainless " Y " definitely louder and sounds great in tunnels for the smile factor i would cut them out (y);)
 

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Premium Member 2001 SLK200K/2001 SLK320
Joined
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2,761 Posts
It is still flowing gases at present, I've just put it back in the garage and the Sun is shining!!!!!!!!!!
😩😩😩
I had been toying with the idea of fitting one of the "emotion valve" diverters like a certain V8 has fitted as I would like a little more roar at times but without a constant drone.

Now I guess I have a lot more options open to me:

Leave as is but empty the cats
Cut them out and straight pipe back to the rear box
New cat back system
Genuine MB or Sports

Need a cup of tea and something to eat while I go internet searching I suppose.

If anyone has an opinion on a good UK available system for a 320 I'd be interested to hear your thoughts.
Al @ADH posted a pic of his gorgeous looking system just a few days ago, J28/Mickey One is probs too far for you to go.. dunno if they do postal or not?

This thread:
 

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Premium member 2001 SLK320
Joined
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811 Posts
Hi All,

I have been noticing an annoying and worsening rattle from the exhaust of over the past few weeks, first chance today to really get under the car to inspect. One of the transmission exhaust mounts was broken which I have temporarily fixed with a large jubilee clip. It made no difference to the rattle so I jacked up the car and firstly noticed that there was no centre rear mount at all but that didn't appear to be creating any problem.
View attachment 594371

However as I was listening I could then clearly hear rattling which appears to be from the secondary cats.
Can anybody help diagnose from the video clips below please?


Allo Jason, the same annoyance happened to me a few years ago on a trip to South Wales. Noticed the rattle on over-run and acceleration. Popped into the mechie on my return trip. About 90 mins later, 2 secondary cat fillings removed,, one of which had started to break up, boxes welded back up, and a lovely, slighltly rortier exhaust sound at about 2000rpm-to 2500rpm where it resonates nicely. No faults since. Passes the MOT clean as a whistle, fuel economy, if anything, slightly improved on a long run ( tbf it's already awesome on those). It had done about 70,000 by then and was 16 years old. Only run on the finest fuels in my ownership.
 

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Registered 2001 SLK320
Joined
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371 Posts
Discussion Starter · #12 ·
Hi Jason i've got 2 x 320s one with the cats gutted and left in situ this made it slightly noisier but not OTT the second is de-catted running a stainless " Y " definitely louder and sounds great in tunnels for the smile factor i would cut them out (y);)
Thanks for the advice, that is exactly what I was thinking. There is an exhaust specialist that has been recommended about 60 miles away so the return journey should sound great! I popped into my local Mercedes dealers this morning and asked for a price for a new MB system for the car (just in case it was one of those "oh that's not bad, cheaper than an aftermarket part" sort of situation); after a bit of a search I was told that the back box is no longer made and MB don't have any, the left hand pipe was £850.00 plus vat and the right hand £400.00 plus vat!!!!!!!!

Wow!! .......to be fair the existing system is 20 years old so the price becomes more palatable if you think of it in those terms, but probably in 20 years time it will be the only bit of this car left :LOL::LOL:.

You say it's definitely louder, but in a nice way I hope? Not like a Civic with 4" drain pipe sticking out the back....
 

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Registered 2001 SLK320
Joined
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371 Posts
Discussion Starter · #13 ·
Al @ADH posted a pic of his gorgeous looking system just a few days ago, J28/Mickey One is probs too far for you to go.. dunno if they do postal or not?

This thread:
Thanks, that is a really nice system, I'll see what the local(ish) guy that's been recommended thinks, I believe that they work to the same sort of standard. Can't believe I missed this thread...
 

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Registered 2001 SLK320
Joined
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371 Posts
Discussion Starter · #14 ·
Allo Jason, the same annoyance happened to me a few years ago on a trip to South Wales. Noticed the rattle on over-run and acceleration. Popped into the mechie on my return trip. About 90 mins later, 2 secondary cat fillings removed,, one of which had started to break up, boxes welded back up, and a lovely, slighltly rortier exhaust sound at about 2000rpm-to 2500rpm where it resonates nicely. No faults since. Passes the MOT clean as a whistle, fuel economy, if anything, slightly improved on a long run ( tbf it's already awesome on those). It had done about 70,000 by then and was 16 years old. Only run on the finest fuels in my ownership.
Thanks for your comments, I'm edging towards removing the secondary cats entirely. I'm hoping to end up with a nice exhaust note that's loud when "going for it" but not too droning at cruising speeds. I may also go for one of those emotion valves for a nice bark on start up.
 

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Registered 2001 SLK320
Joined
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371 Posts
Discussion Starter · #15 ·
Well I spoke to a fabricator this morning and it's booked in to lose the secondary cats and have a stainless section inserted instead on the 20th :p. He estimates about £250 + VAT which is a much better number! @Dave2302 Where did you source the emotion valve that you installed on yours? I'm not going to install that right now, as losing the cats might be enough, but if not that'll be my next move.
 

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Premium Member 2001 SLK200K/2001 SLK320
Joined
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2,761 Posts
That is a better number (y)

Photos when done/being done or it didn't happen :LOL::p
 

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Premium Member 2002 R170 SLK V8 5.0
Joined
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5,144 Posts
Where did you source the emotion valve that you installed on yours?
Stainless Steel, vacuum operated Normally Open Butterfly, note that Normally Open are harder to find ;)

Diameter to suit whatever pipe you are using, it opens for about 4 seconds upon Engine start, then only on Full Kickdown, via a 12 Volt Vacuum Solenoid which dumps the Vac from the pipe that runs front to rear. Also needed is a decent one way Vac Valve for the Vac line teed at Engine end, otherwise it will open when under normal acceleration.

A lot of work to do it nicely, I bought the valve from a UK EBay Exhaust Fabrication Specialist, likely it's Chinese but it is well made, no idea who now, have a search around.

Vacuum Solenoid Valve has to be wired to Ign + and the Earth Signal from Kickdown Switch which is found at Motor ECU on Automatic Trans V6 (and V8) R170 with EGS52 Trans Controller.

If your Car is a Manual Trans, you will need a Throttle Pedal from Auto Car and pick up the Earth Trigger direct from the Kickdown Switch on the Pedal ;)

HTH :)
 
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Registered 2001 SLK320
Joined
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371 Posts
Discussion Starter · #19 ·
Stainless Steel, vacuum operated Normally Open Butterfly, note that Normally Open are harder to find ;)

Diameter to suit whatever pipe you are using, it opens for about 4 seconds upon Engine start, then only on Full Kickdown, via a 12 Volt Vacuum Solenoid which dumps the Vac from the pipe that runs front to rear. Also needed is a decent one way Vac Valve for the Vac line teed at Engine end, otherwise it will open when under normal acceleration.

A lot of work to do it nicely, I bought the valve from a UK EBay Exhaust Fabrication Specialist, likely it's Chinese but it is well made, no idea who now, have a search around.

Vacuum Solenoid Valve has to be wired to Ign + and the Earth Signal from Kickdown Switch which is found at Motor ECU on Automatic Trans V6 (and V8) R170 with EGS52 Trans Controller.

If your Car is a Manual Trans, you will need a Throttle Pedal from Auto Car and pick up the Earth Trigger direct from the Kickdown Switch on the Pedal ;)

HTH :)
Thanks Dave, I appreciate you coming back to me, cheers (y)
 

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Premium Member 2002 R170 SLK V8 5.0
Joined
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5,144 Posts
No worries, I was a bit late replying, normal service is not available right now due to me welding up "the Titanic" atm, (I just bought another R170 v6 for R&D etc) ;)

It is currently stuck on my lift with rear Subframe out, and I need to be able to move it off my lift by Sunday, as the Customers Cars are queing up the Driveway now :ROFLMAO:
 
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