C180 brief Buzzing noise when touch the accHelerator

[ollyk999]

Hi,

Don't know if anyone can help identify what's wrong, and what we can do to sort it out as it's v. annoying!

We have a 2002 C180 and get a strange buzzing noise when the accelerator is touched. Only lasts half a second or so.
Tends to occur in the following situations:
*you've been stationary with your foot off the accelerator - then when you first touch the accelerator to pull away it buzzes
*you have taken your foot off the acclerator to coast for a bit and when you re-apply your foot to the accelerator it buzzes.

When you're cruising normally with your foot on the accelerator there's no noise - mostly occurs around town when your foot is off/on/off/on the accelerator.

Noise comes from the engine compartment. Wonder if it's a valve of some sort?

Has anyone had something similar and know how to cure it?

Many thanks,
Olly

 

[nigel cross]

Sounds like it could be a loose or dirty connector, on the pedal.

 

[ollyk999]

No, it's definitely coming from the engine compartment.
Difficult to describe I'm afraid - sounds like 'biddely buzz' and lasts about as long as this takes to say.
I can only think it's a valve of some sort.

 

[recycled]

is that not the purge regeneration? even though that lasts for quite a while and its more like a click than a buzz

 

[ollyk999]

Thanks for the reply. I didn't know what Purge Regeneration is so I've searched for other posts elsewhere in the forum about it. Other people also seem to describe PR as a 'ticking' noise, so I don't think that's what's wrong with ours.
Thanks for suggesting it though, I'm grateful for any help or ideas I can get!
Olly

 

[classic180]

Hi ollyk999

I searched for months online to see what this noise was and eventually brought the car to a Merc Dealer. (I bought same off a non Merc Dealer who messed around with it for weeks (changing Cam Shaft Balancers (Magnets Keeping Timing Chain in line) etc etc.

What is the Noise then? - its the Timing Chain Pretensioner. I just had one changed on a 2002 C180. it looks like a large bolt (within Small Hole at Top for Oil to pass Through at High Pressure and is Spring Mounted). It screws into the lower lhs of the Engine Block down under the Alternator.

To Replace it, the mechanic has to take out the alternator, water pump and various casing(s). When theyre out - the Pretensior is 'Unscrewed'; the new Pretensior 'Screwed' In and NO NOISE. If left, it will continue to worsen and may / could cause the Chain to Dislodge, Affect Timing (Badly) and Damage Engine.

It cost (Ireland) €750 for the Pretenioner (as some type of Tensioner Arm is also required) and a Merc Garage (in Ireland) would charge about €700+ to put it in.

Luckily I have a Mechanic Friend who did same (after the Non Merc Garage I bought it off had a go and messed up). At the time (due to aforementioned Mess Up), I had my friend Replace the Water Pump, Alternator Belt + A FULL SERVICE. He only charged me €360 (STG250)including the new parts. Shows you the real cost, Obviously you wont have to do same.

Unfotunately though, if it costs c €1,400 in Ireland to do the Pretensioner, then STG1,000 would probably be right.

The Car has never made the noise since. It was as you described a Buzzing Sound which in the end I could delibrately make happen by pressing the Accelator to get the First 'Buzz' Tone, Hold above 2000 revs; and Take my Foot Back up, to get the 2nd Part of the Buzz OR alternatively, Press Accelorator quickly and get the 2 Buzz's togther.

Regards

Classic180


ps. I'm not a mechanic but am interested in all aspects (especially remedying faults on my c180 - My Cruise works (Holds; Accelarates; Deccelarates) between 20 and 30mph, But thats it!!!!.

 

[alibally]

I think this noise could be the variable camshaft gearing. To test this disconnect the solonid magnet and rev it up to just over 1400 rpm and release the throttle. If the noise is away the you need a new inlet camshaft sprocket assembly. (Remember to plug it back in)

 

[classic180]

Camshaft Adjustor Sprocket

Hi

What would happen if you just left same i.e. didnt change camshaft adjustor. I replaced Tensioner but same was initially too tight and car sounded like a Hoover and Under Pressure in any Gear. I have had this remedied and new Tensioner fitted again - Hoover Sound gone but Slight 'Buzzing Noise' is back - I would gladly live with the buzzing noise than the 'Hoover / Under Pressure' Sound.

I disconnected Magnet Solonoid - you were bang on - noise gone away. If I have to have Cam Adjustor changed - Is there alot of Stripping of Engine - Does Sump have to come off (or ) can chain be held in place while Adjustor 'Swapped'.

Regards

M