Silber55

I have a W208 CLK55 which has developed a noticable rattle under light revs while driving. We cannot replicate the sound when the vehicle is parked up or when giving it some real revs, it sounds perfect.

I've found many experts are wanting to charge me for different problems ranging from the timing chain, some sort of cam adjuster, valve covers loose, engine fan clutch, etc.

Any suggestions?

GatorMB

Hey Silber,
A light rattle can be the timing chain and related components like bad tensioner or guides, Crank recripriocating parts like rod, piston, pin, main bearing.
The pitch and depth of the rap or nock will help diagnosing this one.
External noises like accessory bearings are what you wish for though. Get a long screw driver or a pipe and put the blunt side to your ear. Get a buddy or wife to powerbrake the car while you pinpoint the nock, Good Luck

GatorMB

A wishful note: The 208 has some serious backpressure in the exhaust system, This gives us some awesome off the line tourqe. Exhaust rapping might under light load or even start-up can resemble a mysterious nock.

betrezra

You can try to isolate the sound with a long pipe or use a stethoscope....... I've done this *CarefullY* with engine running.... place the probe on an engine accy to see if sound is coming from that item........ rev engine and try to locate.

A bad cat can rattle under light load.


GL>

Chappy

Yes, check your catalytic converters.

ecampbell

If you have had the trans out check the torque converter bolts. If they have backed off, under light load it will sound like excess valve train noise.

Silber55

Thanks to all who have replied. The noise had me worried.

So far the problem appears to be a combination of 109 degree weather here in outback Australia and bad fuel.

A bottle of quality octane booster reduced the noise by a considerable amount. Today is cooler and the noise is barely noticeable under load from 1000~2000 rpm and still totally absent in park or neutral.

GatorMB, the intake/exhaust have been modded for flow.

betrezra and Chappy, I will check the cats.

ecampbell, the trans hasn't been pulled out but it's good to know these things.

At least the noise made me go over the car and not take it for granted.

betrezra

Wow! If it was knocking bad enough to hear that is bad.
I would not do ny spirited driving until that tank of gas is gone.

Deto sounds like a box of rocks from the engine...... I know from my centrif sc days tuning with boost retard and timing light.....

Can you pin point the filling station to the bad fuel?

Silber55

betrezra, no I purred her around worried as. No spirited driving at all.

Box of rocks sounds about right.

She has a new tank of fuel and two bottles of booster. I drove the car hard this arvo and it was great as always. The noise is now gone but...

The previous noise was loud enough to hear with windows down from 1K~2K rpm. I can only imagine the internal scorchmarks due to pinging. Combustion chambers will prob need to be checked.

The servo/gas station is the one we always fuel up at.