checking rear bearings - for potential replacement - PeachParts Mercedes-Benz Forum

kuene · #1 10-05-2016, 05:24 PM

I had my car in a shop that I haven't visited yet - to get a quote on installing some front suspension parts I picked up (but don't feel like installing myself), and to evaluate AC. The owner said (and I agree) that the front suspension is tight and that it seemed ill advised to spend money there. I had purchased a few things since my lower ball joint boots are split and looking super crusty.

But, he says my rear bearings are shot (as well as sway bar links).

I'm not getting the "hum" that I've been told to look for, nor is the guy who inspected the vehicle saying I am. But he says there is too much play in both, more so on the right.

To check these myself, all I do is jack up the rear a bit and try to force some play using a pry bar? is there an acceptable amount? any hard an fast rules? what should I look out for. This is a bummer, if I need to replace.

ThatOne · #2 10-05-2016, 06:38 PM

Quote:

Originally Posted by kuene

I had my car in a shop that I haven't visited yet - to get a quote on installing some front suspension parts I picked up (but don't feel like installing myself), and to evaluate AC. The owner said (and I agree) that the front suspension is tight and that it seemed ill advised to spend money there. I had purchased a few things since my lower ball joint boots are split and looking super crusty.

But, he says my rear bearings are shot (as well as sway bar links).

I'm not getting the "hum" that I've been told to look for, nor is the guy who inspected the vehicle saying I am. But he says there is too much play in both, more so on the right.

To check these myself, all I do is jack up the rear a bit and try to force some play using a pry bar? is there an acceptable amount? any hard an fast rules? what should I look out for. This is a bummer, if I need to replace.

At 114K miles? Right off the bat that seems unlikely. Truth is you can run noisy rear wheel bearing for quite a while, so if they're not making any noise yet I'd be leery of that diagnosis.

With the rear wheel off the ground I would bolt a spare rim to the wheel hub and grasping at 12 and 6 and then at 9 and 3 attempt to push and pull to determine how much play is evident.

Mxfrank · #3 10-05-2016, 07:34 PM

I would think that if there was excessive play in the RW bearings, there would be noise, and lots of it. The sway bar bushings can be checked visually.

OTH, if your ball joint boots are torn, then the ball joints won't last long.

Diesel911 · #4 10-05-2016, 08:27 PM

Quote:

Originally Posted by kuene

I had my car in a shop that I haven't visited yet - to get a quote on installing some front suspension parts I picked up (but don't feel like installing myself), and to evaluate AC. The owner said (and I agree) that the front suspension is tight and that it seemed ill advised to spend money there. I had purchased a few things since my lower ball joint boots are split and looking super crusty.

But, he says my rear bearings are shot (as well as sway bar links).

I'm not getting the "hum" that I've been told to look for, nor is the guy who inspected the vehicle saying I am. But he says there is too much play in both, more so on the right.

To check these myself, all I do is jack up the rear a bit and try to force some play using a pry bar? is there an acceptable amount? any hard an fast rules? what should I look out for. This is a bummer, if I need to replace.

Taking the rear hub out to get at the bearings generally damages the bearings and it is it would be an expensive job to have it done by someone.
There is a dial indicator reading for the in and out play of the rear hub (als for the front wheel hubs). The end play is 0.04-0.06mm

You could safely lift both rear wheels off of the ground supported on Jack Stands and run the Engine with it in gear spinning the rear wheels and listen to the Wheel Hub for any grinding noise.

If the Ball Joints are tight the boots can be replaced.

If the mechanic was speaking of the Plastic Sway=bar Links being shot they are not a big issue.

I don't know if anyone has done it with success but if there is too much end play on a Rear Wheel Bearing it is possible to tighten it up re-setting the end play and then drive it and see if it makes noise that indicates the bearing/s are no good.

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kuene · #5 10-05-2016, 08:53 PM

Car is 114k, but it was hit in rear right in 1998. The arm and possibly some other components on there now came from an older car - 76 or something. I know this from some writing visible on the arm. I wouldn't be surprised if at least right rear hub has more miles than rest of chassis.

I'll do some more diagnosis, but why do I need to put a spare rim on it?

I feel the same about ball joints and cracked boots, this guy in particular won't take my money to install them. I had bought a new rubber boot and was thinking about replacing the super deteriorated one but not sure if I can do that while it's in place?

ThatOne · #6 10-05-2016, 10:37 PM

Quote:

Originally Posted by kuene

Car is 114k, but it was hit in rear right in 1998. The arm and possibly some other components on there now came from an older car - 76 or something. I know this from some writing visible on the arm. I wouldn't be surprised if at least right rear hub has more miles than rest of chassis.

I'll do some more diagnosis, but why do I need to put a spare rim on it?

I feel the same about ball joints and cracked boots, this guy in particular won't take my money to install them. I had bought a new rubber boot and was thinking about replacing the super deteriorated one but not sure if I can do that while it's in place?

I use a spare rim because it allows a better feel and more leverage when trying to rock the wheel hub in it's bearing. A wheel with a tire is just more difficult to grasp and feel what's going on especially when there's just a tiny bit of movement.

You can't do the ball joint boot R&R without separating the ball joint from the lower control arm, but if you can get that done you'll be able to pull the old boot off and slip the new one over the ball joint's stud.

Diesel911 · #7 10-06-2016, 12:38 AM

http://www.peachparts.com/shopforum/diesel-discussion/323469-lower-ball-joint-separator-w123.html

Note since this thread is old the price has likely changed.

kuene · #8 12-12-2016, 05:39 PM

update:

Driving on highway yesterday, and I'm really listening now since the shop's diagnosis a few months ago. At above 60mph or so I start to faintly hear (maybe feel) a low, slowly pulsing hum, from the rear of car likely the right rear. Is the tell-tale hum a super low pitched hum? This may have always been there since I acquired the car back in April 2016, but I'm only now looking and listening for it.

I still can't tell from pushing/pulling on the rim what kind of movement (if any) I'm getting, though I might try with a gauge once I get a base. If this is the beginning of the tell tale bearing hum, what's the consensus on how much time/miles I have until this becomes a critical problem to sort out? Is driving more with this likely to quickly lead to other, worse problems with the hub? Could my wheel fly off at speed?

Ugh.

kerry · #9 12-12-2016, 06:28 PM

How did the mechanic diagnose a bad real wheel bearing? Without knowledge of the exact process of diagnosis and confidence it was correct, I wouldn't worry about it until more symptoms emerge.

SD Blue · #10 12-12-2016, 06:39 PM

A close visual inspection of the inner bearing seal might tell you more.

I had a slightly noisy one and found the inner seal was hard and dried out.

Diesel911 · #11 12-12-2016, 06:53 PM

I used to be an mechanic and were a sound is coming from is difficult to pin point.

The Axles can make noise, the Differential can make noise (has the fluid level been checked) the Drive shaft carrier can make noise and the transmission.

You could safely get the rear of the Car jacked up so the wheels are off of the ground and you can get under the Car. Use a mechanics stethoscope or a section of broom stick with your ear over one end and the other end on the part you want to listen to. Of course watch out for moving parts.
Put the Trans in gear and listen for abnormal noise. When bearings are bad they sometimes make a grinding sound.

Also you cannot feel the in and out pay of the rear bearings.

Mxfrank · #12 12-12-2016, 07:54 PM

Usually a wheel bearing noise becomes more obvious in hard turns. When you turn left, the right bearing is loaded up and is more likely to complain. Turn right, the opposite.

I tend to agree that if the noise isn't loud and clear, it's not too bad.

kuene · #13 12-13-2016, 03:16 PM

It's not too loud, and I only sense it when I'm above 60.

Checking the diff oil seems appropriate. If I refer to the maintenance manual on checking diff oil (I have an 82 300d) (see page here --> https://www.dropbox.com/s/se4d705lbfvewxj/3510.pdf?dl=0 )

do I need to check both of those filter plugs/ports identified by the arrows in the drawing?

EDIT - Oh I think I get it. Top one is for checking/filling - bottom on is for draining.

Diesel911 · #14 12-13-2016, 09:21 PM

Quote:

Originally Posted by kuene

It's not too loud, and I only sense it when I'm above 60.

Checking the diff oil seems appropriate. If I refer to the maintenance manual on checking diff oil (I have an 82 300d) (see page here --> https://www.dropbox.com/s/se4d705lbfvewxj/3510.pdf?dl=0 )

do I need to check both of those filter plugs/ports identified by the arrows in the drawing?

EDIT - Oh I think I get it. Top one is for checking/filling - bottom on is for draining.

People recommend making sure you can remove the upper plug first as the upper plug is frequently the one that is frozen in place. That means if you drian the differtial and cannot remove the top plug you cannot fill it.

kuene · #15 12-14-2016, 09:37 AM

Got it, thanks Diesel911. Going to check it first, if levels are up and it resembles oil, I'm prob not going to drain it.