Noisy above 75

[martindmsmith]

I have aW212 250cdi 2011 with the 5 speed autobox. The car is in good condition with no known mechanical issues. However on the motorway at any speed above 75 (so circa 2250 rpm) the engine,.or possibly the exhaust, becomes very much more notceable, to the point where it is too intrusive. I don't think this can just be because the engine is revving higher than it does under the 7 SPD gearbox. I have had this engine and drivetrain in a c class before and that car could sit at 80 all day long. The car otherwise feels absolutely fine and if it is running down hill at that speed (IE the engine is not under load) the car is whisper quiet. The gearbox changes smoothly and my mechanic can see nothing to suggest a problem with the exhaust. Does anyone recognise this issue please ?

 

[Wighty]

Cheap worn tyres ?

 

[SL63 Mark]

However on the motorway at any speed above 75 (so circa 2250 rpm)

I don't think you want to be admitting to driving over 75 mph on a public forum.

I would edit to say "over a certain speed".

 

[martindmsmith]

I have aW212 250cdi 2011 with the 5 speed autobox. The car is in good condition with no known mechanical issues. However on the motorway at any speed above 75 (so circa 2250 rpm) the engine,.or possibly the exhaust, becomes very much more notceable, to the point where it is too intrusive. I don't think this can just be because the engine is revving higher than it does under the 7 SPD gearbox. I have had this engine and drivetrain in a c class before and that car could sit at 80 all day long. The car otherwise feels absolutely fine and if it is running down hill at that speed (IE the engine is not under load) the car is whisper quiet. The gearbox changes smoothly and my mechanic can see nothing to suggest a problem with the exhaust. Does anyone recognise this issue please ?

Hello all. Thanks for those who offered answers. I took it to a local independent specialist who was able to diagnose the issue within 2 minutes. Worn gearbox mount. Apparently a very common problem. £35 part and 30 minutes labour.

 

[mioba]

Hello all. Thanks for those who offered answers. I took it to a local independent specialist who was able to diagnose the issue within 2 minutes. Worn gearbox mount. Apparently a very common problem. £35 part and 30 minutes labour.

Just reading I was to suggest a mount.

Now go drive above 75 mph and get it tested.

Ignore driving miss Daisy with hi SL63!

 

[00slk]

You should hear the noise in my old campervan above any speed! not sophisticated these old French 4 cylinder diesels like a 320 L6 diesel

 

[Srdl]

Hello all. Thanks for those who offered answers. I took it to a local independent specialist who was able to diagnose the issue within 2 minutes. Worn gearbox mount. Apparently a very common problem. £35 part and 30 minutes labour.

That’s the benefit of using a Mercedes specialist. Experience and common sense makes all the difference.

Welcome to the forum, by the way,

 

[martindmsmith]

That’s the benefit of using a Mercedes specialist. Experience and common sense makes all the difference.

Welcome to the forum, by the way,

Absolutely. Class Cars in Sandwich for anyone in that part of the country