Hmm...does my diagnosis make sense?

[jagec]

So fairly recently I noticed that at low speeds (10-30mph), there is a rhythmic sound coming from the right rear of my car. It's something between a scrape or a squeal...more like a scrape at lower speeds, more like a squeak at higher. It varies in loudness, frequency, duration, and cycle with speed, so it's certainly something attached to the axle/rotor/wheel. It's hard to tell whether it's the sound of rubber sliding across metal, or metal on metal...I suspect the latter. Further experimentation determined that (a)It only happens once the car's been driven for a few minutes, not when it's cold, (b)It disappears whenever I'm accelerating, even very mildly, and (c)It doesn't change at all when I apply the brakes, push in the clutch, or shift to neutral. Anytime I'm decelerating or coasting, I start to hear it around ~30mph, and it just gets more and more slow and drawn-out as I continue to slow down.

So I think that it's a CV joint in my driveshaft (RWD car, MR layout). The boots look fine, if stiff and aged, but that's the only thing that seems to make sense to me given the symptoms. Suspension work has recently been done on this car (replaced shocks and bushings all around, new tires+rims), and the sound kinda-sorta showed up at the same time, but that doesn't really make sense, so I think it's a coincidence.

Question: Is it at all possible to tear into/rebuild/grease-up a CV joint, or is it pretty much a replace-only option? How about taking the boot off for inspection? Or am I completely wrong and there's another perfectly reasonable explanation for the symptoms I listed?

 

[Colt45]

CV joints don't usually make noise like that. Do you feel slop when you punch it or let off quick?
Chances are if the boot is intact the joint is fine.

My guess is that a dust shield is rubbing on a rotor, or something trivial like that.

 

[jagec]

Originally posted by: Colt45
CV joints don't usually make noise like that. Do you feel slop when you punch it or let off quick?
Chances are if the boot is intact the joint is fine.

My guess is that a dust shield is rubbing on a rotor, or something trivial like that.

That's what I thought, but why would it make a difference if I was on or off throttle?

As for slop, it's hard to tell. The car's almost 20 years old. It certainly doesn't seem sloppy, but the EFI response immediately on- and off-throttle is rather abrupt when it transitions to/from fuel cut-off. In my experience this is common to all Japanese cars of that era. Makes it harder to tell if anything mechanical has too much give.

And yeah, I didn't think it was a CV joint either at first, I thought it was a wheel bearing. But, again, I don't see how that could disappear when I go on-throttle.

 

[jagec]

So...no thoughts, huh?

Today I adjusted the valves, hoping to cure a ticking problem that I figured was loose valves. Nope...all in spec, save two that were tight. It's not timing, either, since that was adjusted. I think it might be injector noise. The joys of an older car I guess.

At least I can do all my own work...that helps.

 

[soydios]

my '94 Jeep periodically chews up a front CV-joint boot, and it manifests itself as a faint squeaking sound matching tire speed under 25mph or so. mine manifests itself only when turning to the left, but goes away when I even lightly touch the brakes.

 

[jagec]

I didn't have enough time to take a close look at the problem before doing a Bay area -> Seattle drive.

Now there are additional symptoms! Oh boy!

Halfway through the drive, I stopped for gas, and noticed a low thumping coming from the RR, in addition to the squeak. I took it out of gear, and the thump disappeared, but the squeak persisted. I tried this a couple more times...yup, thump shows up under engine braking, disappears under acceleration or when taken out of gear. Squeak remains in all situations. I felt the rotor at the station, and it seemed that the inside edge was hot, but the rest of it was cool.

So, CV joint AND bent dust cover, I'm guessing. Guess I'll have to start hitting up junkyards.

The last part of the trip took place in a driving rain. I noticed that I could no longer hear any of the sounds when I came to a stop in the stuff. I guess rain fixes it. Since I live in Seattle, maybe I should just put off the repair until the summer.

 

[Slacker]

Get a reman axle if it is the cv joint, I have seen what a messy pain in the ass it is to rebuild a cv joint.

A reman axle should be anywhere from $75 to $150

 

[Zenmervolt]

I hate, hate, hate to say this, but it also could be differential noise.

Could also be a wheel bearing.

See if the noise changes during hard cornering. That tends to be one of the indicators for a wheel bearing, though they tend to make noise all the time and not just under power.

Unfortunately, sound that changes depending on whether you're accelerating, engine-braking, or coasting does tend to mean something in the transmission/differential, but I'd still say to check the CV's and the wheel bearings first.

A general way to check CV's without inspecting them is to grab the axle and see if there is any fore-aft/up-down slack in the joint. You should be able to move the axle laterally somewhat, but you shouldn't get any significant movement at all from a shearing force applied at 90 degrees to the axis of rotation.

ZV

 

[jagec]

Originally posted by: Zenmervolt
I hate, hate, hate to say this, but it also could be differential noise.

Could also be a wheel bearing.

See if the noise changes during hard cornering. That tends to be one of the indicators for a wheel bearing, though they tend to make noise all the time and not just under power.

Unfortunately, sound that changes depending on whether you're accelerating, engine-braking, or coasting does tend to mean something in the transmission/differential, but I'd still say to check the CV's and the wheel bearings first.

A general way to check CV's without inspecting them is to grab the axle and see if there is any fore-aft/up-down slack in the joint. You should be able to move the axle laterally somewhat, but you shouldn't get any significant movement at all from a shearing force applied at 90 degrees to the axis of rotation.

ZV

The thing is that it seems to be very much to the right side of the car...and since this thing's MR and the right axle is the longer of the two, I'd think that any differential noise would seem to be coming from directly behind the driver if anything. Hard, tight corners do seem to change the noise somewhat, but the complete lack of noise under acceleration really doesn't seem to support a wheel bearing diagnosis. Maybe I should go to a bit parking lot and have a friend drive tight circles while I ride on the engine bay to get a better idea of where exactly the sound is coming from.

I pulled off the wheel and rotor a couple days ago and gave it a look, made sure the dust cover wasn't contacting the rotor, and moved the CV joint around a bit. The axle is able to move in and out a very slight amount, but that may be within normal tolerance, since it has to take up suspension movements to a small degree. I couldn't get a good enough angle to tell about fore/aft or up/down. Trying to spin the hub while holding the axle steady seemed to indicate a slight amount of slop, but it was hard to tell for sure. I'm getting more and more convinced that this is the CV joint, although I still haven't seen any boot damage. The rubber's pretty stiff, though, it could have a small crack that I just am not noticing.

My favorite local junkyard doesn't get MR2s very often. I'll have to keep an ear to the ground, as well as in the MR2 boards. I'm hoping I can get something for $10-20, but I have my doubts.

 

[Zenmervolt]

Originally posted by: jagec
Maybe I should go to a bit parking lot and have a friend drive tight circles while I ride on the engine bay to get a better idea of where exactly the sound is coming from.

If you do that, you are required to put a video of this up on YouTube for our amusement when you fall off the car.

EDIT: Just a random thought. I have no idea whether this is true, but I've heard that the MR2 shared a good bit with the Corolla. Is it possible that the axle shafts are interchangeable? Or was that limited to the first generation cars?

ZV

 

[jagec]

Originally posted by: Zenmervolt

Originally posted by: jagec
Maybe I should go to a bit parking lot and have a friend drive tight circles while I ride on the engine bay to get a better idea of where exactly the sound is coming from.

If you do that, you are required to put a video of this up on YouTube for our amusement when you fall off the car.

EDIT: Just a random thought. I have no idea whether this is true, but I've heard that the MR2 shared a good bit with the Corolla. Is it possible that the axle shafts are interchangeable? Or was that limited to the first generation cars?

ZV

I own a mk1, so if true I may be in luck. But I doubt it would share exactly this part, because the corolla was FWD at that point, and I don't think they'd have exactly the same axle assembly for a non-steered wheel. Worth checking out, though. THanks!

 

[Zenmervolt]

From some digging, the Mk1 MR2 uses the same C50 (pre-1987) or C52 (1987 and later) transmission as the Corollas of the time (makes sense, transverse engine with transaxle, easy to drop in a MR car). Don't know about the half-shafts though. Still, worth looking into.

You wouldn't believe how many "Volkswagen" parts I can use on the 914 that are identical in every way except price and scarcity to the "Porsche" parts. Hopefully this is a similar situation for you.

ZV

 

[jagec]

Nifty. I'll have to keep that in mind. I'm surprised I haven't heard more about this from the pre-87 guys...that C50 transmission is prone to 5th gear popout when it ages, and it's a direct swap to the C52, which is not.