Roaring 1988 300 SE
 

Hi everyone,
Car has approx. 138,000 miles on it. Has a slight roaring sound while moving down the hi way. Seems to increase with speed from about 20-30mph to around 60 or 70. Is constant, even through shift changes. Also markedly more noticeable when slight steering pressure applied to left. Applying pressure to right and roar almost completely dissappears.
Any ideas out there amongst you good folks as to what I should look for. Changed right engine mount yesterday. Left engine mount is ok. Two brand new tires on front, rears 90% tread left.
Thanks for help in advance.............

Could be a wheel bearing if its a roaring sound.....or a bad CV axle or something.

Check the front tires for wear (esp. cupping on the inside or outside edge of the tread). When was the last time you had an alignment? If the tire has started wearing funny it will make a hell of a lot of noise down the road. This is usually indicative of tie-rods etc in the front end.

I had to go through all that on my w124 a while back. It turned out to be the tie-rods (which I replaced) and the control arm bushings (which the dealer had to cut off w/ a torch...that was pricey...). All fixed now, though.

Thanks for the feedback, y'all. I will check the tie rod ends. The last alignment was less than 2000 miles ago. New tires on front. 90% on the rear. Wednesday, when the new tires were installed, it did seem that the roar was more pronounced.

How much anguish is involved in changing the front wheel bearings?

They're relatively easy. As long as you don't over or under tighten them.

It's the Rear Wheel Bearings that will test your patience (and your non-PG vocabulary).

Did you physically run your hand on the front tires to feel for cupping?

Sorry, didn't read that part.

I'd still check the new tires for odd wear (it can happen pretty quick).

Front bearing are fairly cheap & painless, so that would probably be the easy thing to do first and see if it solves it.

I vote for either tire or wheel bearing.


What kind of tires did you put up front? It's not unheard of for brand new tires to have issues such as a busted belt.

Swap your fronts and your rears. If the problem stays the same, it's probably the wheel bearing. I am of course assuming that you have ruled out slop in your tie rods and other steering components.....



-tp

Thanks again folks. I think I've narrowed it down to front right wheel bearing. I really do appreciate all the feedback.

One more question on the wheel bearings. As I do not yet own a service manual, how tight should the front wheel bearings be? Thanks again........

Tighten the bearing lock nut (on the end of the spindle) until its difficult to turn the wheel, then back it off like 1/3 turn....or until the wheel turns easily again....it doesn't take much. Its a pretty tight spec.

Then lock the little allen bolt on the lock nut. Don't forget that!

usually is front wheel, rear wheel u need to turn harder to bring out noise.
if proportion to speed= wheel , power train.
Engine usually prop to revs.

Hey, you guys are great. Thanx so much for the answers. Hopefully I can return the favor sometime. Will change right front wheel bearing this wkend and post results. Thanks again.........gschira

Gschira, there is a factory spec for wheel bearing play (0.01-0.02 mm) using a dial indicator on the rim, and pulling/pushing in/out on the wheel. However, I have found this approach to be subjective at best, even with a very good dial indicator and stand. Most of the guys on here use the method mentioned in the earlier post; tighten the nut up snug to remove any play and grease buildup, then loosen a bit. Then grab thre top and bottom of the tire and pull back and forth; you will feel the play in the bearing. Snug the nut until there is just a tiny tad of discernable play when you tug on it.

After replacing and adjusting bearings, drive it awhile and recheck; sometimes the races reseat a bit under the loads of driving.

DG

I have been wondering about something all this time. While checking for a bad wheel bearing, should I feel some play when pulling on the tire (top and bottom)? There is none on the suspect bearing. It is good and snug. However, giving it the ole hand spin trick, I can hear some slight growling that I don't hear on the opposite tire. This growling is distinctively different than the occasional brake pad/rotor rub sound.