Identify this noise

[Christien]

Can anyone identify this noise?

http://cledroit.googlepages.com/noise.mp3

It's coming from the rear passenger side - I'm thinking it may have something to do with the brake caliper, because it only happens during deceleration, however it continues to make noise even after I've released the brakes. It never happens on acceleration or at idle. I had a look at the rotor and it doesn't look scored, though I was just looking through the wheel - haven't had a chance yet to take the wheel off and have a look. There's no change in braking, acceleration or shifting whatsoever - everything feels perfectly normal.

Thanks for any help!

[leadrsa729]

Are you driving the 72 T? Check the oil system out there on the passenger rear side outside of the engine bay. It sounds like an awful lot of clattering going on back there though. Good luck tracking it down!

[Joe Bob]

CV Joint?

[Christien]

What in the CV joint does it sound like? A bad bearing?

[stevemfr]

Picture a stone in your rear tire tread clicking on each revolution - that's what a worn CV joint sounds like. I had a real hard time hearing anything on your mp3 - do you mean the rattling noise? To irregular for CVs...

[sc_rufctr]

Originally Posted by stevemfr

Picture a stone in your rear tire tread clicking on each revolution - that's what a worn CV joint sounds like. I had a real hard time hearing anything on your mp3 - do you mean the rattling noise? To irregular for CVs...

x2... I don't think that's the CV joint internals but the bolts holding them onto the wheel flange. The bolts could be loose and they're cocking sideways when accelerating. When this happens the drive shaft is out of alignment with the centre of the hub... Result >> Irregular rattle.

Whatever it is take the wheels off and have a good look. Double check everything back there.

BTW: That engine sounds great... Old school hotrod!

[Christien]

If it sheds any light on anything, the engine was recently out (for a transplant) and the CV joints were of course disconnected and reconnected. I packed fresh grease in and used new CV gaskets. I first noticed this noise on the way home from a track day, which is why I was thinking it might have to do with the brake caliper. However I noticed today listening more closely that the sound is there sometimes under acceleration or steady throttle, though not as consistently as it is under braking.

I'll pull the wheel off as soon as I get a spare 20 min. and have a look.

Peter, thanks, I think it sounds great too! It's an upgraded 1967 2.0L transplant while I rebuild my 2.4.

Thanks for your help so far!

[kokenm]

Is it in the middle of the car or the rear. maybe a stabalizer bar that is loose.

seems kinda odd but were you on a smooth road when you recorded the noise?

[Christien]

Hard to tell if it's in the middle or rear, but I'd say rear. It's definitely behind where I sit and off to the right. No sway bars, front or rear, so it's for sure not that.

When I made that recording this morning, it wasn't the smoothest of roads, no, but I've already put that one to the test and the noise occurs on smooth and bumpy roads.

[RSBob]

Without a doubt, that is the sound of money leaving your wallet.

[Christien]

Oh, I don't doubt that, I'm just hoping it's 10's and 20's, not 100's!

[Christien]

Ok, I finally got a few minutes to go out and pull the wheel off. I was unable to replicate the noise by just turning the wheel/axle. I pushed on the brake pedal a few times, then went back to turn the wheel hub and no noise. Also, the wheel bearing passed the "wiggle the wheel" test. The only thing that looked like it might be a problem is it looks like the caliper may not be fully opening. I don't know what the clearance should be between the brake pad and the disc, so I took as good of a pic as I could:



And one of the rotor from a bit further out - doesn't seem to show any signs of scoring or anything:

[fbarrett]

Sounds like a loose CV joint. Clean the inside of the bolt-head sockets well before inserting a fresh (un-buggered) allen-head wrench and re-torquing the bolts. If the engine has been out recently, and the mechanic re-used the old bolts to save a few bucks or neglected to clean them well, their sockets may have been unable to take full torque, and he may have just let it ride...

Frank

[Christien]

Ok, I'll give that a shot this weekend. I pulled and reinstalled the engine myself. I didn't use new CV bolts (never heard that you should, to be honest), but I did retorque them after the first 500km or so (as I always do). I've driven maybe 2000km since then. Hell, if the problem is that simple, I'll be a happy man!

[trekkor]

I also thought CV before reading any of the posts.

Double check the torque of each bolt.


KT

[jonbot]

Tranny/Motor mount? Sounds like something banging against the the underside. Let us know what you find.

[Christien]

Is there a specific torque spec for CV bolts? I've always just tightened them pretty much as tight as possible.

[trekkor]

Is there a specific torque spec for CV bolts?

Oh yes!

You'll need to reference a shop manual.
Too tight is bad as well. They can stretch or break.
Your bolts may also require special one time use 'Schnorr washers' like on the 914 ( 901 box )


KT

[kodioneill]

There is no way that the caliper is making that sound. CV joint or emergency brake shoes maybe! Check for worn suspension components, loose shock etc...

[Christien]

Did some testing this afternoon with a friend in the backseat, then we switched. It's definitely coming from the area of the tranny. He thought it sounded like debris rattling around in the heat exchangers or something, but with a bit more driving, we were able to determine that the noise only occurs under weight transfer to the front, and maybe a bit to the right as well. This explains why my first thought was the brake caliper. But it would still occur when letting off the throttle quickly without braking, which ruled that out.

I'm going out to the garage now to drain the tranny oil and see if anything comes out. I'd be surprised if something did, though, because it's shifting and driving absolutely fine. (tranny was rebuilt last winter)

I'll report back with any findings.