Noise when accelerating - 1994 C180...

[Robert Cox]

Trying to eradicate the gremlins in this car I've recently bought.

Engine is smooth and quiet when first taking off from rest, but when the tacho reaches about 2000 rpm, speed approaching 60kph, there's a "ticking" noise coming from somewhere, a bit like pre-ignition (although I'm using premium unleaded). Disappears at about 3000 rpm.

Does anyone have ideas on this?? I did read an old archive posting from the US mailing list commenting that such a noise could be "exhaust resonance" and that MB had no solution for it. Anyone heard of this?

Any help greatly appreciated.

Other than this and the vacuum leak (other posting), I love the car...

 

[pluggers]

Trying to eradicate the gremlins in this car I've recently bought.


Does anyone have ideas on this?? I did read an old archive posting from the US mailing list commenting that such a noise could be "exhaust resonance" and that MB had no solution for it. Anyone heard of this?

Does it still make a noise when stationary and you rev the engine?
Dont know about the exhaust resonance,could possibly be an injector thats noisey.

 

[pluggers]

Had another thought on this,maybe it could be the cam chain or tensioner.Ive heard rumours that the tensioner can give up after a while.

 

[Robert Cox]

Thanks for your thoughts.

No, it doesn't seem to make the noise when stationary. And my wife listened as I drove away the other morning, and it seems to come from the middle of the car, rather than the engine.

If the chain tensioner was not doing it's job, wouldn't I get a rattle when coasting, when the chain was slack, rather than when accelerating? Just a thought...

 

[pluggers]

I seem to be running out of ideas at the moment,All I can think of is a rattly catalytic converter or the heat shield around it,Or this may sound daft but it has happened to me twice now.Have you got something stuck in one of your tires.When this happened to me at low speed you could only hear it with the window open(a slight metallic tap tap) till you got to say 50mph then the wind noise would drown it out.

 

[Robert Cox]

Funny that... I did have a screw enbedded in one of my tyres (first puncture in 20 years!).

But no, this is definitely related to engine speed. As I'm accelerating in 3rd, as soon as the tacho exceeds 2000rpm the "tick-a-tick-a" starts, and as soon as 4th engages and the needle on the tacho drops below 2000, the noise disappears.

But thanks for all your thoughts... I would take it to a Mercedes "stealership", but there's only one in our small city (I'm in regional Victoria) and they are rip-off merchants, and don't treat customers of 9yo Mercs nicely at all. They don't want to know you.

I'm currently driving the car gently in case it's doing something bad. At first I thought it was because I was using plain unleaded 91 RON fuel. I read the owner's manual which demands premuim 95 RON. But putting that in hasn't made a scrap of difference.

Do 1994 C180s need premium? (I didn't think we had such stuff in Oz back then - my 1986 W124 230E runs fine on plain unleaded even though the manual says to use 98 RON!!)

 

[Robert Cox]

Funny that... I did have a screw enbedded in one of my tyres (first puncture in 20 years!).

But no, this is definitely related to engine speed. As I'm accelerating in 3rd, as soon as the tacho exceeds 2000rpm the "tick-a-tick-a" starts, and as soon as 4th engages and the needle on the tacho drops below 2000, the noise disappears.

But thanks for all your thoughts... I would take it to a Mercedes "stealership", but there's only one in our small city (I'm in regional Victoria) and they are rip-off merchants, and don't treat customers of 9yo Mercs nicely at all. They don't want to know you.

I'm currently driving the car gently in case it's doing something bad. At first I thought it was because I was using plain unleaded 91 RON fuel. I read the owner's manual which demands premuim 95 RON. But putting that in hasn't made a scrap of difference.

Do 1994 C180s need premium? (I didn't think we had such stuff in Oz back then - my 1986 W124 230E runs fine on plain unleaded even though the manual says to use 98 RON!!)

 

[Spike]

Is the noise a sort of dieselish sounding mettalic rattle when under load at low revs?

If so, it is likely to be the little shock absorber on your belt tensioner assembly causing the problem. Not exbenzive or hard to replace and quite a common problem.

 

[Robert Cox]

Thanks Spike... I'll definitely check that one out, as my W124 had that problem when I first bought it. I'd forgotten that one. (My wife said she "thought" it came from the middle of the car, but it's hard to tell. She also reckons it sounded more like "Pa Pa Pa Pa" than "Tick-a Tick-a Tick-a", that I tend to hear inside the car.)

 

[Spike]

middle of the car????

The only thing there that springs to mind is your CAT - mebbe its breaking up internally or with a pinch of salt it could just be the shielding making the noise.

 

[pcman_jh]

Rattling

My 1994 C250D had a rattle around 2000 revs. It was caused by two things - totally unrelated.

The first was the lower exhaust mount had broke away from the exhaust pipe just before the cat. You couldn't see this with the eye becuase it took the grunt of the engine to show it broken. If you give the pipe a good shake, look for the bracket moving next to the pipe. If it's sheared away, new exhaust I'm afraid.

The second was the heat shield that's attached to the underbody above the exhaust. One of the mounting pins had lost its retaining nut, causing the heat shield to rattle (very tinny in sound). A plastic rawplug and glue was all that was required to effect a repair.

 

[Robert Cox]

Thanks.

Yes, I'm definitely leaning towards the noise being exhaust-oriented. It could even be a slight leak as there's a "hiss" associated with the ticking sound. Definitely, not the engine. I revved it over 3000rpm while stationary and there's no noise at all. It needs a "load" to show itself.