What would cause a vibration that seems to be a cabin area vibration.
What is your question?
When I drive the car, starting at about 35 to 80 mph, I get a harmonic cabin vibration for about 35 - 40 miles. It even happens on a newly paved 6 miles stretch of brand new highway. It begins to dissipate the further I drive. On my way home I get no vibration or its very faint no matter the route I take. Started about 4000 miles ago with no changes made to the car. Car has 31,000 miles new tires with 10000 miles on them and the rims have been check for being out of round by dealership and re-balanced the tire twice. It driving me nuts? Transmission Mount? Flex Disk? Any suggestions?
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first question , have you test driven with an MB tech and duplicated the noise/vibration for them? Do they find it a normal characteristic , or do they agree , something is wrong?
I have had them ride with me on several occasions. They agree that there is a clunk sound coming from the rear of the car when I put the car in gear and release the brake. They also agree there is an unusual vibration but cannot say where it is coming from. The hunt for the problem has resulted in a early transmission service for $530 that had no effect, two tire balances @ $150 and several days of my time. Every time I take the car to them they claim they can't find the problem. They state that as long as the problem is intermittent there is not much they can do. Currently i don't have the ability to reproduce the problem at will.
I'm sorry to say , but unfortunately , if it is intermittent , and they cannot reproduce the symptom(s) in order to diagnose it , it will be near impossible to diagnose. Short of them continuing to guess at it (all be it educated - they should know basic characteristics of their product) , I would suggest (not that you haven't already)continue keeping a journal of when and what conditions it occurs under , like you already have , and IF/when it get more consistent , bring it in and drive with them. One last random thought , if possible (I work on primarily Honda- quite different from Benz!) , can it be run with the car in the air to see if it will act up after free-spinning for a little while?,
I'm happy to report that I have found the solution to my particular problem. Now this may sound a bit odd but it resolved my problem for more than a month now. I was running around like crazy on this but this is what I did.
While reading a few forums I ran across a guy talking about tire pressure. For a minute I though, really? That's the first thing you check when you have a tire problem. Well, I was right and wrong at the same time. Here's how. Inside the door of my car is a small chart for your front and rear tire pressures for the car that are recommended by the manufacture. I can only imagine the pressures only apply to the OEM tires that came on the car new. So, believing I know what I'm doing, I ran these pressures in my tires. Why? Because that's what posted in the door jam silly
Well, to verify I'm running the right pressure I decided to make sure the recommended pressure label on the car matched the tire manufacturer's recommended pressures. Here's where it gets interesting. The only pressure on the tire is the MAX tire pressure of 51 psi. Continental only recommends that you don't exceed the max pressure not a recommended cold tire pressure for your cars weight. What an Ah Ha! moment for me. This was a 21 psi difference in what I was running in the front tires and 17 psi on the rear.
I decided to increase the front to 35 psi and the rear to 38 psi and drove the car for a few days. What a difference in the ride and handling! In the end, the car rides as smooth as glass @ 38 front 42 rear. No more steering nibbles and the cabin vibration is all but gone.
My theory is as follows; the tires would develop flat spots when the tires cooled because of the underinflated condition. The centrifugal force created by the tire rotation would cause the tire to hop because of the out-of-round condition. Combined, the under inflation and flat spots was causing the harmonics or vibration. This explains why the condition was always worse the first 30-40 miles of driving (flat spots) and cabin vibration/harmonics (under inflation) at highway speed all the time. There is no scientific evidence to support my theory but, the proof is in the ride. ;0)
I have had them ride with me on several occasions. They agree that there is a clunk sound coming from the rear of the car when I put the car in gear and release the brake. They also agree there is an unusual vibration but cannot say where it is coming from. The hunt for the problem has resulted in a early transmission service for $530 that had no effect, two tire balances @ $150 and several days of my time. Every time I take the car to them they claim they can't find the problem. They state that as long as the problem is intermittent there is not much they can do. Currently i don't have the ability to reproduce the problem at will.
I'm sorry to say , but unfortunately , if it is intermittent , and they cannot reproduce the symptom(s) in order to diagnose it , it will be near impossible to diagnose. Short of them continuing to guess at it (all be it educated - they should know basic characteristics of their product) , I would suggest (not that you haven't already)continue keeping a journal of when and what conditions it occurs under , like you already have , and IF/when it get more consistent , bring it in and drive with them. One last random thought , if possible (I work on primarily Honda- quite different from Benz!) , can it be run with the car in the air to see if it will act up after free-spinning for a little while?,
I'm happy to report that I have found the solution to my particular problem. Now this may sound a bit odd but it resolved my problem for more than a month now. I was running around like crazy on this but this is what I did. While reading a few forums I ran across a guy talking about tire pressure. For a minute I though, really? That's the first thing you check when you have a tire problem. Well, I was right and wrong at the same time. Here's how. Inside the door of my car is a small chart for your front and rear tire pressures for the car that are recommended by the manufacture. I can only imagine the pressures only apply to the OEM tires that came on the car new. So, believing I know what I'm doing, I ran these pressures in my tires. Why? Because that's what posted in the door jam silly Well, to verify I'm running the right pressure I decided to make sure the recommended pressure label on the car matched the tire manufacturer's recommended pressures. Here's where it gets interesting. The only pressure on the tire is the MAX tire pressure of 51 psi. Continental only recommends that you don't exceed the max pressure not a recommended cold tire pressure for your cars weight. What an Ah Ha! moment for me. This was a 21 psi difference in what I was running in the front tires and 17 psi on the rear. I decided to increase the front to 35 psi and the rear to 38 psi and drove the car for a few days. What a difference in the ride and handling! In the end, the car rides as smooth as glass @ 38 front 42 rear. No more steering nibbles and the cabin vibration is all but gone. My theory is as follows; the tires would develop flat spots when the tires cooled because of the underinflated condition. The centrifugal force created by the tire rotation would cause the tire to hop because of the out-of-round condition. Combined, the under inflation and flat spots was causing the harmonics or vibration. This explains why the condition was always worse the first 30-40 miles of driving (flat spots) and cabin vibration/harmonics (under inflation) at highway speed all the time. There is no scientific evidence to support my theory but, the proof is in the ride. ;0)