W124 e320 vibrating....about to give up
 

Hi...

I have changed the A/C compressor lately (1 week) and I am starting to notice a new problem. After I drive for 30 min on highway speed(140+ kph)
the car starts to vibrate continously, seems when it heats up. The vibratio is max when I stop the car. I looked and found the exhaust to be vibrating as well as my engine.

I took the car to a mechanic in the evening after it had cool down, but all the symptoms were gone. He checked the exhaust and the engine and found they were OK.

But today morning again after 30 min of highway driving the problem reappeared again.

Any help is highly appreciated.

motor mounts, i had the exact same problem on the same vehicle, changed the passenger side mount, as per many posts on this board, and the vibration was gone!!!

Thanks for the reply,

It sounds better than a suggestion by a mechanic here, who said that something has gone inside the exhaust.

I change the mounts and see.

tacobell, replace both mounts when you do the job.

well, maybe, but why doesnt it vibrate when it is cold if it is the motor mounts?

i was going to suggest the engine is missing. to check that you need to (carefully) pull each spark plug wire off and see if one doesnt slow the motor down. if you find one that doesnt you have found your miss.

then if you find a miss, first check the plug. replace it.

if that doesn t do it check the plug wire by changing it with one that is known to be good.

after that i would check the fuel injectors by switching them around.

and finally it might be a burnt valve i suppose which will get worse when it is hot and the valve is longer, though with hydraulic adjusters this may not apply.

any of these things is a lot simpler than just changing the mounts if you arent for sure that they are bad.

good luck

tom w

Thanks for the feedback,

I am not suspecting the motor mounts, because I changed them less than two years ago, when the vibrations that time were continous, wether the car was cold or hot, and they would dampen when the gear is in neutral.

But this aint the case now, were the vibrations are much stronger and neutral has a very minimal effect, and they only occur after the car has heated up.

But as walgamuth suggested, I will change the plugs since I havent changed them for the last 3 years. I will try cleaning the injectors and see what happens.

Is the valve walgamuth mentioned inside the engine itself? And is its remedy if burnt simple/cheap.

Thanks

The valve(s) Tom mentions are the intake and exhaust valves for each cylinder. Replacing the valves would involve pulling the cylinder head and inspecting the condition of the valves and valve seats ... relativley expensive and likely not a job you'd want to tackle. Before pulling the head you need to diagnose the root cause of the engine vibration. Have your mechanic check the engine performance when the engine is hot and vibrating. If he's unsure then get a second opinion. You want to avoid doing unnecessary and expensive work. Better to pay for a correct diagnosis than replace parts haphazardly. Consider taking your car to a local MB dealer for diagnosis if you're uncomfortable with the independents' recommendations.