Help to diagnose car vibration

fangio3

Hi
My wife has a 2013 Mercedes SLK with only 19,000 miles on it.
We have an oscillating vibration which is evident from around 65mph upwards (particularly evident at constant speeds on motorway).
The vibration lasts for around 1.5 seconds, then 1.5 seconds without vibration, then repeat. It is there all the time and doesn't appear to change with road speed.

I have changed the wheels and tyres (going from the standard 18 inch to 17 inch) with no change to the vibration.

The car has past it's only two MOT's fine, so no evident play in any of the bushes, ball joints etc.

Any ideas?

reddwarf2002

The nature of your problem would mean that it's very unlikely to be related to anything suspension/bearing/tyre related. It's more likely to be a fault with the operating mode of the ECU and any faults within the engine that is causing it to run poorly.

I'm not sure how often the ECU switches between rich/lean cycles but if it did switch every 1.5 seconds and there was an issue with your engine with either fuelling, spark (if petrol) or air mixture then it would probably cause the car to run unevenly (oscillating vibration).

System

Best of luck with it, it could be a myriad of things although you've eliminated what I'd have expected with our pot holed road network.

Even though it has passed a MOT it could still be worn bushes although unlikely unless the car does a lot of town driving.

Could be brake discs

Could be clutch

Could be crankshaft.

Could be gearbox.

Could be what the above poster has listed.

In short could be from any rotational part on the vehicle with any mass and it is unlikely to get diagnosed on a general forum. See if there's a SLK owners club website with an active forum and ask on there. If it is a common issue there will likely be at least one person who has found the issue.

fangio3

I doubt it's a common SLK issue and I've tinkered with cars myself for over 40 years and know this isn't engine related. It's definitely something causing an harmonic vibration, possibly a bad shock. I have a feeling this has been present since new and the previous owner even didn't notice it (no motorway driving), or sold the car because of it.

caprikid1

Personally I would stick it in for another MOT and tell them you are suffering vibration and can they see anything, maybe at MB ?.


For the cost of an MOT they might just pick something up that is inside tolerance for MOT but causing it.


I spent best part of 10 years chasing wheel vibration on a Ford Capri, eventually I identified it to be the dust shields I had fitted to the wheels , always removed them to balance the wheels, fitted them when I get new wheels etc. Feel foolish looking back !.

facade

Most of the rotating components have harmonic dampers nowadays- is one missing, worn out or fitted wrong?

SomethingAboutMoney

Shot in the dark.

Have a look in your engine bay, there could be a stray bit of metal laying snug somewhere.

Lorian

Does it stop if you dip the clutch?

fangio3

It's an auto. Though I'm pretty sure it's not engine related. I think either prop, prop centre bearing or shocks. But just wanted some other opinions.