Hi All-

Those of you that may know me and were following my last 'no start' thread. Know that I've been shipwrecked for the last couple weeks with an asthmatic jag. Its now back running and has a new problem. NEAT -_- 01 XJ8 112kmi

Symptoms: Rear wheel noise. A steady grinding, with an abrasive wash, that increases in volume with speed and matches the cabin air noise around 65mph.

Circumstances: The car was running perfectly before its no start incident and was laid up for two weeks, just sitting. Surrounding temperatures range from cold to very cold, here in NY. (Single digits to negative)

What I've done so far: Lifted the car for a visual inspection and quick tire shake. (cause not found err404) Removed rear brakes to inspect caliper health and pad health. I found no defects, and replaced the rear pads. (cause not found err404)

In the other posts I've read I have found the same symptom with a range of causes varying from; wheel bearings, differential bearings, to the driveshaft center bearing.

Current logic line: Ferris Bueler. Lift the car, free wheel the drive line, use a stethoscope to inspect each bearing for integrity. *Do not push out window*

Thoughts or recommendations?

Thank you all,

-Mitch

 

Mitch,

That's a good next step. With the rear end supported on jack stands and the front wheels securely chocked on both their front and rear sides, you can check all the bearings - just take care not to touch any rotating parts with your stethoscope probe, and do as much of your probing as possible while lying beside the car - spend as little time as possible under the car.

Be safe and let us know what you find.

Cheers,

Don

 

Hey Don-

Thanks for jumping in. In your opinion what do you think is the most likely culprit here?

-M

 

Well, to paraphrase Sherlock Holmes, it's unwise to have preconceptions or assumptions, but from your description, my first guess would be a wheel bearing. My experience with diff output shaft bearings is that they howl, but any grinding is inaudible in the passenger compartment, and diff pinion bearings produce a jet engine whine that rises with road speed but may disappear when you let off the throttle. If you had a vibration problem I'd suspect the driveshaft center bearing or flexible coupling. But the grinding noise makes me suspect a wheel bearing since you've ruled out a worn brake pad grinding on a rotor (and I assume you checked the inside faces of both brake rotors? There I go assuming again...).

If I'm really wrong, Sherlock will never speak to me again!

Cheers,

Don

 

Don-

You are correct about it being best to not assume. Something I should remind myself of more often.

I did check the inside of the pads for any unusual wear of course all looked well.

Your thoughts on those individual bearings and their symptoms mirrors my own thoughts in triplicate.

Thanks, Ill keep you posted. Again no garage it may be a couple days before I can get back to you.

-Mitch

 

Mitch:
I always like to review "what happened just before the problem?" I cannot remember the pad configuration on a rear brake pad, but have you made certain you put it all back together right? I put a pad in backwards on my LR Discovery once...

 

Last post, last problem, you said: "Now that its running. One of my rear calipers is a little frozen from being laid up so long but, I'll remedy that soon enough."

What did you do to fix that? Or is it still hung up and could be the noise source?

My car has zerk fittings on the Ujoints. I had those greased and had the diff oil changed: I am still hung up on the idea that old cars find lots of problems when the temp goes below zero F.

Bowing to Don's superior knowledge: Wonder how accurate a reading of the wheel bearings you will get without them being loaded. Maybe the tire shop you used has a Hunter Wheel balancer that leaves the wheels on and weighted against the balancer's drive: would give you a better cut than parking your butt under the car with wheels free spinning.

My $.02

 

At the risk of being alarming, it sounds very similar to the noise I experienced which turned out to be the diff oil having disappeared over the years and, I assume, never checked when the car was serviced, either by a Jag dealer when under warranty or later by indie garages. I ended up having a reclaimed rear axle fitted.

 

Hey Ross- Before the problem was all the way back before my last post. Nothing to report. Its a brand new sound after sitting for 2 weeks. As for the calipers, yea they're back together all right, simple enough job. Both calipers working just fine too. I checked them by giving the breaks a little pump and moving the calipers in and out. They function properly.

Hey Jim- Yea I looked at the problem last night. This problem is what I thought I heard. (if that makes sense) Took both calipers off and serviced the brakes. They're working just fine. The thought of my diff being out of fluid hadn't occurred to me. I guess its most certainly a possibility. No fluid on the ground where it was sitting. Any way to check or is it like an old school pumpkin just take the back off and see?

I was wondering the same about getting a proper response without them loaded. I wouldn't even do it with the wheels on, because I need the access. Overall I think its an easy enough test can't hurt to try. You never know, I might just get it all spinning and go, "oh yea there it is!".

Hey Nigel- Thanks for the alarm. Without anyone saying it, I might have ended up having to buy a new diff myself.

Thanks fellas,

-Mitch

 

Jim, thanks for your kind words, but I'm just another shadetree mechanic like most of us. I certainly haven't run into every possible situtation, but in my limited experience a bad wheel bearing that is audible from the driver's seat will be easily identified with a mechanics stethoscope with the wheel off the ground and spinning - just touch your stethoscope probe to any part of the hub carrier and compare the left and right sides. The bad side will be obvious. It's not necessary to remove the wheel.

Before you even start the engine and put the transmission in Drive to check with the stethoscope, you can check for wheel movement by grasping each tire at 12 o'clock and 6 o'clock and alternately pressing and pulling with each hand and watching for excessive movement in the wheel. Watch carefully because it's easy to mistake tire deflection for wheel movement. Compare both rear wheels for reference. If one moves noticeably more than the other, it's probably your culprit.

 

Hey Fellas-

Reporting back. Did the Ferris Bueller Test today.

I've needed the car this week, so I've sort of been forced to drive it. Since my original post the identifiable sound has gotten quieter.

So tonight I put the car in the air and had zero wiggle room on the rear tires. No play whatsoever. I took off my tires, calipers and rotors to remove as many possibilities for mistaking the noise.

I couldn't replicate it. Both wheel bearings (both sides) sounded the same and both sides of the pumpkin sounded identical. The center bearing made almost no noise at all.

Right now I think that over the two weeks it was laid up, one of the bearings developed some condensation and some rust, within the bad bearing itself. Now that I'm driving it daily it's started to remove that coating and go back to not being so noisy.

Recommendations? The diff being dry has not left my mind either.

Thanks,

-Mitch

 

Hi Mitch,

A few thoughts come to mind. One is that, with the rotors and wheels removed, there is very little load on the bearings, especially the outer ones, so you may not have gotten a true sense of their condition.

You mention that both of the diff output shaft bearings sounded the same... were they fairly quiet with no grinding sounds?

What prompted you to think the diff could be dry? Did you see any signs of oil leaks at the pinion, either output shaft, or the rear cover?

Your theory about the one or more of the bearings rusting while the car sat for a couple weeks could be valid, but would imply that those bearings are both short of grease and subject to water ingress, so if you're right, you'll need to remedy the situation as soon as you can figure out where the noise is coming from.

Please keep us informed!

Cheers,

Don

 

Hey Don-

Thanks for sticking around. I thought the same thing about having the wheels on or off for the test. I didn't quite have the time to run both as odd as that sounds. I thought that regardless of load the culprit would be fairly easy to spot. No so much.

Both of the diff output shaft bearings seemed to have normal noise. Fairly quiet with a definite sense of movement within. No real grinding, just the noise of rotation. To put my findings into a different perspective. All of the bearings had an almost identical sound during the test.

Onto the possibility of a dry diff. The only line of reasoning I have for that is that I don't that much about the history of the car. My instincts tell me to shy away from that largely because: 1) This popped up after sitting for two weeks. 2) I've had no leaks at all and the diff looks dry. 3) This is a new noise and I think if it were going dry I would've heard it prior to this incident.

Some new news: It seems to be temperature related. Driving it this morning it was much different than driving it home last night. The temp yesterday was about 23. The temp this morning was only about 5. It was noticeably louder this morning. I'm sure that Jim Hartz will nod when he reads that .

Looking at the manual and some online photo's. The bearings in the diff look pretty beefy. I would be very surprised if I changed wheel bearings on both sides and either didn't identify the problem right away when I took the bearing apart or the noise was still there after reassembly and test drive. I hate to throw part$ at a problem.

Thoughts?

Thanks,

-Mitch

 

I would guess those rubber doughnuts (forgot what they are called) are very hard when it is really cold and are not absorbing the shock as well as when warm and are sending the vibration noise down the drive shaft.

Got the same problem with the upper front shock mounts (the neoprene gets really hard and smaller in very cold weather) they rattle when it is cold, dead quiet when warmed up (Jag engineers had a reason for that ugly orange rubber crap they used in OE mounts).

Still, take it to Midas and get the diff oil changed.

 

Hey Jim-

I thought you would be interested in the temperature being a factor. I think I'll keep driving it for a little while see what happens. Probably take it over and get the diff fluid changed just to rule it out. It can't be that much $$.

How much was it when you went?

Thanks,

-M

 

About $60 or so. Had the fuel filter changed at same time, I've forgotten which was which.

 

You may consider taking the diff vent off and cleaning it- see if that helps. It is on the top and of the diff and (fairly) easy to access with an open end wrench.