Tinny Rattle when Accelerating

[The Fat Baron]

Hi all,

I'm a new member, been lurking for a good while, but would really appreciate some help on this problem. I recently sold my 97 C180 which ran like a dream except for a kind of rattling noise that appears to come from underneath the car when accelerating. The car I sold was a manual with 100k on it. I've since bought an AT with 50k and have started to notice the exact same noise on this one. The harder I accelarate, the louder the noise gets. It's a tinny kind of rattle but doesn't sound too serious, it's just annoying. Anway, reason i'm on here is that i'm wondering is this noise standard on C180's. The fact that it's happened twice makes me wonder. I had brought my frist one to a mechanic a year or two ago but he was unable to fix it.

Any info would be much appreciated.

Cheers.

 

[turnipsock]

Could be anything. I would check the exhast clamps at the manifold first.

...or you could try not accelerating.

 

[The Fat Baron]

Thanks turnipsock.

That's exactly what it sounded like so I checked it but no joy.

I could try your second option but it might impair my enjoyment of the car a little :grin:

 

[nasher]

have you checked the entire length of the exhaust to see if it's touching anything? Worst case scenario is the cat's broken internally, this happened to our Alfa recently

 

[bundy]

tinny rattle

i have heard on many occasions slight pre ignition under hard acceleration on c180/200 models merc technical claim this is quite normal & nothing to worry about. hope this helps.

 

[The Fat Baron]

Thanks for your responses. Gives me something to go on.

 

[pentoman]

Yes, it sounds like knocking, pinking or pre-ignition (all the same thing).

Worth getting it looked at anyway, or if you use higher octane fuel it will probably go away.

 

[OlafMaxwell]

Sounds distinctly like pinking to me.....does the engine management system not prevent that? While it may be passed off as normal it is not good for an engine, if it is happening best to lay off the right foot and go easier on the engine.

I am not sure about cats because I drive diesel but the way we eliminated that before cats came in was to use premium/high octane petrol. I don't know if you can put LRP or some other premium grade in or if it will damage CAT. If you can do it this is one way of checking it out. I do know there are some high octane unleaded petrol outlets, could be worth a try.

 

[The Fat Baron]

Thanks again guy's.

I tried the 98 octane and while it hasn't completley cured it, it's certainly vastly improved so that's definatley the problem. Trouble is the high octane is 28 cent more a litre. Can this problem be fixed or do I just have to live with higher fuel costs ?

 

[aceface]

I would check your exhaust cat
I had a similar problem with my '97 W140
Replacing exhaust cat solved it

 

[OlafMaxwell]

I see you are based in Ireland.....are you using one of the MB dealers in Dublin......Worth checking also if the diagnostics are right......If you are in Dublin check with the exhaust shop in Townsend St, under the railway bridge right turn off Pearse St just after railway bridge, ask for Dominic Sheehan and tell him who referred you....and no, I don't get 10% commission....he does tyres too....

 

[turnipsock]

If the fuel makes a difference, then it's probably related to the ignition timing somehow. I would get that checked.

 

[OlafMaxwell]

I would not spend money on a new CAT without first running a full check on the ignition timing. My bet is that is where your trouble is. Higher octane fuel will reduce or eliminate it but at a price. Pinking is not good for an engine and you should drive more gently until you get it sorted out. My experience of MB dealers has not been good, only one I found any good was Tom Murphy's in Waterford. There is a German chap out in Minane Bridge near Cork and I know lots of people swear by him, anything from 190 to W124 to CLK and SL.

 

[The Fat Baron]

Terry Jackson in Shankhill is just down the road from me. I've heard he's good but pricey. I might try him first but thanks for the referral. I have been taking it easy if for no other reason then the noise just sounds terrible. I'll let you know when I find out the cause.

 

[Robboc180]

Hi - Had the same problem on my 1995 c180, looked through the owners,s manual and found a cure - underneth the windscreen washer fluid is a black cap about the size of a 20 pence piece pull this and pinking should stop, it did on mine.

 

[Bolide]

Pre-ignition

If the car's pinking I'd replace the plugs & get the timing checked. Does it run hot or overheat?


Nick Froome
www.w124.co.uk

 

[EdGasket]

Hi - Had the same problem on my 1995 c180, looked through the owners,s manual and found a cure - underneth the windscreen washer fluid is a black cap about the size of a 20 pence piece pull this and pinking should stop, it did on mine.

Resurrecting this old thread as I have definite pinking on my 98 C180 with 113K miles. Any attempt to accelerate under load makes it pink unless I change down gear more frequently and use higher revs but that is not my style of driving and my cheap and cheerful Hyundai does not have this problem even if I put my foot down in 5th gear from a low speed.

What exactly is the black cap thing referred to in the above post and what does 'pulling it' do? I don't know if it still applies to the 98 model but I will have a look.

Anyone know if the knock sensor ever goes faulty or is there any way of testing it?