Looking to find out

For a 550 what are signs that motor mounts need to be replaced?

Tx

 

What symptoms does your car display that makes you believe you have bad motor mounts?

 

No issues presently just want to know what to look for as there have been some reports of R231 motor mount failures.

appreciate anyone advising what they noticed that clued them into determining that the mounts needed replacement as I am in warranty up to 75,000 miles/7 yrs and they will be replaced if needed

 

How many miles on your car? Very doubtful, if you’re asking about the 2018 SL550….
I haven’t seen any widespread issues with the r231 mounts. There have been one or two internet posts about issues (and I would question motor mount diagnosis on cars with less than 40k that have not been raced or abused), but nothing widespread like r230. The motor mounts have also been redesigned. Although defective or loose parts can never be out of the question. Motor mounts on the tension side will typically fail first. The compression side usually will last much longer.

The easiest way to VISUALLY diagnose a broken motor mount without getting under the car.
Put the car in the street or somewhere where the forward path of the vehicle is clear.
Lift up the hood, start the car.
With your foot on the brake AS HARD AS POSSIBLE SO IT WILL HOLD THE CAR IN PLACE.
Put the car in drive.
Accelerate and look to see if you see the engine lifts excessively.

If it lifts excessively or “clunks” your motor mount(s) is/are bad. Visual inspection under car can also yield clues such as oil leaking out of the motor mounts, or the way the engine sits on the mounts can be another clue.

pro tip: DO NOT have your wife (or anyone you like) stand in front of the car while you do the acceleration test 😀

I give every car I get the audible “clunk” test.
With the windows down, I find a strip of road right next to a wall, I mean, not even an emergency lane, but right next to a wall. Then at 20mph to 30mph or so, I accelerate, decelerate and brake multiple times. Car should be quiet. If you hear any noise, clunking, squeaking etc… You’ve probably got something loose or excessively worn. Suspension, braking and mount issues can all make sound and it’s a no cost method of determining any potential issues. These cars should drive quietly.

Good Luck!

 

The 2018 now 23,000 mi, the 1986 560SL 32,000 mi.

Didn't really think I had any issues just curious how others check.

Tx for your input....makes sense

 

Idle and near idle vibration

 

The R230’s had a consistent problem with the mounts. The mounts were re-designed for the R231.

 

Mine were replaced under warranty at 21,000 miles. Had a vibration in steering wheel in D at idle. Dealer replaced the transmission mount first, no change in vibration and then the motor mounts. Vibration gone.

 

Did dealer give you any explanation as to why the mounts failed with such low mileage (21K mi)...... fact that your engine is 6 cylinder and lighter than a 550 I would expect greater longevity than 21K miles.

Wonder what "crconsuting" has to say bout this??

 

Haha, well, this is an Internet forum. That means anything I say is worth less than the paper it’s printed on. 😀
That being said, no one is immune from defective parts from the factory or a vehicle with a past history. Even service can have it’s issues. I’ve seen cars slip on floor jacks onto engines or cars even lifted from oil pans by accident 🙁

The fact that rmorin49‘s symptoms (vibration felt in steering also) went away after they replaced motor mounts would validate that it was indeed motor mount failure. How it failed is an entirely different question.

and as Utopia Texas stated, they have been redesigned for the R231.

 

I would imagine that the motor mounts average life depends on the type of roads the car is driven on. If it’s mostly smooth highway driving that’s a lot different than those driving in the city full of potholes and things that can jar the engine while driving.

 

Doing some drag racing from light to light or beating on the car will have a big impact on motor mount life

 

75K here on 2013 SL550 and my car guy states that they do need replacing, his actual words were, "not broken, however more stretch than normal". He told me this also over a year ago and cant say I'm getting excessive rattling or vibration noises apart from a noise coming from the instrument panel somewhere which goes away after about 10 mins. Wondered what the av costs were plus labor charges as hear this is no small job to get new if and when the time comes? I'm also told that the right side air intake duct has separated. Thx.

 

Diagnosing such issues over the internet can be difficult.
At 75k it’s possible your mounts are moving more than new mounts would. As I stated earlier, history and driving habits (as well as design) have large influence on motor mount life.
If you trust your car guy, he’s on site looking at it. So he’s in the best position to properly diagnose. It may be worth getting a second opinion if you’re leery. I described earlier (post #4) how to visually check for engine mount movement but that may require a some prior experience of what “normal” engine twist/movement should look like.

If it’s truly right side (US passenger side). I doubt the air intake duct is related. Firstly, that would be the compression side. The tension side (left) would probably move the most and be where the duct might be most likely to separate. The reality is, the glue on those ducts fail over time and they become more prone to separation every time you do an air filter change.

 

I don't recall any dealer comments other than they will replace them under warranty.

 

"fact that your engine is 6 cylinder and lighter than a 550 I would expect greater longevity than 21K mile"

True, if the mounts are the same as the ones on the "550"....