[luckyinpa]

1999 4matic e320.

gf had told me she heard groaning so i listened while she drove in the driveway and thought it was one of the front brakes . pulled off both wheels and nothing obvious. then for some reason i told her put in N when she coasted backwards. sure enough. it sounds like springs on a 20 year old car groaning. like a suspension noise. she hears the noise regularly while driving and i heard it while we went around the block. but in the driveway we again had her put it in R then take it out and put it back in and when it's in N, it doesnt make the noise. the way our driveway is its just easier to test in R than D. but since she drives in D of course it makes the noise then

so any ideas what kind of noise goes away when you are in N? i really hope nothing to do with trans or 4wd

also would this be safe to keep driving

 

[SkippyJasper]

If the motor mounts are over 80K old they may be collapsed.
There's a test you and daughter can perform preferably on level ground.

The observer needs to assume a safe position on either side of the front of the car.
Engine running, hood open, foot on brake place in D and rev slightly and watch to see if the drivers side of the engine raises excessively, say three inches. If so, it's motor mount time along with the transmission mount.

If the mounts are OK, then the question will require more input from you.

Does it occur while car is stationary or only when moving.

Does it vary with engine speed or road speed?

Let us know.

Skippy

 

[luckyinpa]

engine barely moved an inch and she had it up to 1500 rpm

she says the noise is different forward and back. it changes when you accelerate. she called it a chirping sound. when in R its more of a screech, which sounds like bad brakes, but it's not and it goes away when you put it in N.

all this only happens when moving. sitting idling all is well.

 

[SkippyJasper]

Presuming that there is no steering pull while driving its starting to smell like driveline problems.
Couple more questions.

How many miles on car?

What is the known maintenance on the trans and transfer case?

Skippy

 

[luckyinpa]

i think 170K ish . zero known about maintenance. it was bought , driven a month, then sat 2 years until this summer. my mechanic inspected it so its 100% legal but that doesnt mean nothing broken lol.

she told me 2 years ago when she did drive it, there were a few times where it wouldnt come out of first but she thinks she recalls o2 sensor being put in.

 

[SkippyJasper]

Tell us about your DIY skills and the knowledge of your mechanic with MB's.

I'm less concerned with the two year non-driven time as I owned a '98 that sat in a garage for seven years. Much less mileage and it served me well for five years until it moved on to my daughter.

The rub is that there are countless ways to spend dollars on these and not get a useful solution. No need to walk that road if possible.

Skippy

 

[luckyinpa]

my garage is well established and they are good but i dont know their specific MB experience. they will never rip you off but they arent cheap. if you pull in and they cannot find anything wrong they dont charge you. i had what i thougth was brake issue in my car and they did a bunch of stuff and didnt charge me.

ive always had chevys and this is what i do myself. rotate tires. oil change. i can change radiator, water pump, alternator. heater core (it was a 70 dodge so pretty easy). change brakes and rotors and ive even repacked bearings but that is not fun.

i do not play with brake lines or electrical stuff/diagnosis and never would do AC work. i have replaced an exhaust on my jeep myself including putting on a new cat.

 

[SkippyJasper]

Sorry I referred to your gf as daughter.

Your skills sound fine. Isolating the noise is the next challenge.

What my crystal ball says is center bearing on the rear driveshaft. Problem is that there is no easy way to prove/disprove short of taking the driveshaft off - not a casual task.

I'd start by confirming the transfer case has sufficient fluid. It's like most gear boxes where the fill line is the upper bolt. Plenty of examples in this forum. Especially refer to the Stickies at the top.

If you can get all of the wheels of the ground (at the same time lol) you may be able to isolate the noise. Of course unloaded is different than moving the vehicle so a bit of a shot in the dark.

While you are rolling around under the car, observe the hard rubber disks that connect the trans to the driveshaft and the driveshaft to the rear axle. Look for cracks especially around the bolts. This may provide a clue as to maintenance.

On my '98 the center bearing pooped out around 90K though it was not noticeable unless it was winter with the temp under 20F. It would squeak/squeal for a couple of miles and then the noise would go away.
Once I had the driveshaft off it became clear that the bearing was dry as was the sliding joint on the driveshaft. New bearing and new grease fixed it. Too bad I hadn't done that when i replaced the rubber disks several years earlier.

HTH, Skippy

 

[luckyinpa]

hmm i may not be able to even do that much. getting 4 wheels off. assume for a moment it is what you say, can she drive it until the garage can look at it in a couple of days.

 

[SkippyJasper]

Hard to advise from a distance. You will need to use your best judgement based on the noise and your experience.

I will say I drove my squeaky car for several months at 40 miles/day before I did the work (and it wasn't freezing). In my case the noise dissipated so it was easier to ignore.

Skippy

 

[luckyinpa]

my guy couldnt reproduce any noises while on the lift. before he put it on the lift he did drive it and hear it all. but after it was on the lift he said drove it again and heard nothing

charged 50 for time spent and said he could start ripping things off but it sounds like is in the drivetrain and he said he could possibly have to drop the exhaust and its possible parts may not be available for the car this old. he said you can drive it without worry except it will get louder and you may get vibration and then at that point you must get it fixed.

so she's gonna try to minimize driving for now i guess. anyone that tries to buy it will hear the noise no doubt so unsure we could even get the 1300 we put into it back. then theres even if you buy a car for 3K will it be as 'reliable' but maybe it would be easier to fix lol. plus in spring we know will be over 1K for the AC to be fixed i'm sure. so all this is not looking good.

besides the mercedes dealer, which i'm sure she cannot afford, i only know of one other place that advertises all the foreign cars around here. unsure if its worth going there or not. what say you?

 

[SkippyJasper]

Just to be clear for me ; he drove it before putting on the lift and heard the noise. After the lift work he drove it and the noise was gone?

Or

The noise disappeared when it was driven on the lift and reappeared off the lift?

Skippy

 

[luckyinpa]

before entering the garage it was test driven and made all the noise, on the lift it made no noise, test driving after the lift it made no noise

when we get it tonight maybe it wont make anymore noises and they fixed it!

i cannot even imagine what book time is for driveshaft...was he saying exhaust comes off as well to get to it?

 

[SkippyJasper]

Presuming it's like my '98 I needed to remove the rear rubber hangers on the exhaust which let things lower enough to gain access. That was a sedan and I supported the exhaust to avoid too much strain on the rest of it.

As for the no noise on the lift, I find that useful information.

My inclination would be to replace the front and rear differential fluids along with the transfer case fluid. This allows a look a several important variables for noise. The fluids need to be examined for metal particles (little fine pieces would be expected. A large quantity of material would be an indication of severe wear).

For a price comparison I recently had the same fluids replaced at the dealer while a steering rack was being fitted. $360. This is on the ML320.

 

[luckyinpa]

Presuming it's like my '98 I needed to remove the rear rubber hangers on the exhaust which let things lower enough to gain access. That was a sedan and I supported the exhaust to avoid too much strain on the rest of it.

As for the no noise on the lift, I find that useful information.

My inclination would be to replace the front and rear differential fluids along with the transfer case fluid. This allows a look a several important variables for noise. The fluids need to be examined for metal particles (little fine pieces would be expected. A large quantity of material would be an indication of severe wear).

For a price comparison I recently had the same fluids replaced at the dealer while a steering rack was being fitted. $360. This is on the ML320.

thanks for the magic 8 ball. she has not a lot of money so would have to rely on the mechanic to decided what to do. i wont go in and tell them what to do and pay for something that may not be the solution. she said the one noise is gone in reverse but it think while driving she said it was more noisy on the way home.

i guess she can call the guy about 15 min away that says mercedes/audi/vw/volvo etc. though i know nothing about the shop. and i dont know if they will have any better ideas.

 

[SkippyJasper]

Sometimes I've found I need to wait for noises to become evident enough to pinpoint the problem. Probably not the best way of diagnosing, but it does beat heaping monies replacing good parts.