Mysterious noise driving me crazy!

On my last few cruises in my FFR Roadster, this strange noise has developed.
It sounds like a low brake pad warning indicator, although it is more subtle, and no where near as irritating. It is also intermittent. Sometimes I can drive for a half hour or more, then it will suddenly start up. Other times if I come to a stop it will disappear, then start again later. It always disappears when I slow to less than 15-20mph.

The pitch and volume do not change if I step on the brake. It happens if I am coasting out of gear, foot off clutch, or in gear with clutch in. It does it regardless of what gear I am in, and doesn't vary, sound wise, regardless of the speed I am going. Revving the engine makes no difference, in gear or out.

I have the Ford 88 T-Bird turbo coupe 8.8" rear end, with the self adjusting rear disc brakes. 3.55 gears, professionally shortened drive shaft, with new u joints. The rear end was also torn down and rebuilt, all new bearings, crush sleeve, properly shimmed to specs, torqued and checked with a dial run out indicator, etc, etc.. I mention this as the sound seems to be coming from the rear of the car. Hard to say exactly, as the side pipes are loud.
The brake pads front and rear are barely worn, although they do spew a lot of dust. Part of the price for getting good stopping power.
I have jacked the car up, and given it a thorough visual inspection, nothing obvious, IE rub from e-brake cable, etc.
I checked my e-brake adjustment and the cable is slack enough to fully release the pads. Initially, I though there may have been some debris stuck between the pad and the rotor, so I pulled the wheel, (which loosens the rotor) wiggled the rotor, and tapped the caliper with hammer, hoping something may fall out. I may have to pull the caliper and pads and check further but the sound doesn't change one iota in either volume or pitch when on the brakes, or off, so I question this being an area of concern.

I have greased all my u-joints, and rear suspension, evn sprayed a little silicone lubricant up into the rear pinion seal area, as this was suggested as a possible culprit. I also heard of the rear tranny seal drying out at the yoke, so I smeared a tad of grease on the yoke near the seal.
Still no difference.

I don't know whether to just keep driving it and see if the sound disappears mysteriously as it appeared, or to start tearing things apart.

I was hoping that some of you may make suggestions as to where to start, or if you have had a similar issue, that you solved..
I have just less than 2500 miles on the roadster since completion

Thanks!

PS, why do this sites smilie's invade the left portion of the area I am posting to? I cant use the scroll bar either? Bit of a pain..

Reminds me of a rather frustrating noise on my '01 Indian Chief.

Turned out to be my jacket lapel ( snap ) beating against my helmet.

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Originally Posted by Chev malibu

On my last few cruises in my FFR Roadster, this strange noise has developed.
It sounds like a low brake pad warning indicator, although it is more subtle, and no where near as irritating. It is also intermittent. It does it regardless of what gear I am in, and doesn't vary, sound wise, regardless of the speed I am going. Revving the engine makes no difference, in gear or out. I have just less than 2500 miles on the roadster since completion Thanks!

PS, why do this sites smilie's invade the left portion of the area I am posting to? I cant use the scroll bar either? Bit of a pain..

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I'm wondering if the pads are being applied as things heat up. Ever so lightly, you mention large amounts of brake dust but nothing else obvious. Did you assemble the car? Is it possible that the push rod into the master is mis-adjusted? Or, is a brake line to close to the exhaust? Things to look into possibly.

The smileys do the same on my laptop, you can try changing the resolution (screen size) , on my home PC with the larger monitor it's fine.

I had a similar issue that ended up being my rear tires rubbing on the bed box. The s10 rear end was too narrow (2wheel drive) for the bed. Had nothing to do with rpm or speed just road condition and some turns.

Idler/tensioner pulley on the serpine belt?

What type of brake pads are you running??? Were they seated correctly according to the manufacturer's specs??? Occasionally a hard spot on a pad can make some really strange noises and the hard spots come from improperly seating the pads or the wrong type of pad for your driving......

I appreciate the suggestions, thanks!

I wish it was as simple as my jacket rippling in the wind..lol.. or even tire rub.

I did break the pads in correctly, when I completed building the car and first put it on the road. I have an adjustable M/cylinder push rod, and there is some slight slack at the pedal, so I doubt that it is applying any pressure.
I have heard of brake fluid expansion from lines exposed to header heat, but would think that would have been an issue from day one? As well, I shielded my lines, exactly to prevent that possibility, as I was aware of that issue.

My serpentine belt is tightened manually, rather than by a belt tensioner. I checked the belt just in case it had stretched, but it seems nice and tight still. I would think if it was the belt that the sound would vary with rpm's, as well the noise wouldn't disappear when speeds are below 20mph, or be intermittent as this is..


I managed 2300+ miles without this noise present, so presume it's something that has just recently changed. If it was an internal rear end issue, I would think the sound would vary with speed, likewise if it was a tranny issue. I heard of a similar instance of a pilot bearing causing a strange noise, but again presume that rpm, would change the pitch. I would hope too, that a brand new pilot bearing would last longer than 2400 miles..

I keep thinking, what moving part on a vehicle, would not be affected by speed, or engine rpm? It's also not affected by whatever gear the vehicles in, or even coasting in neutral? And why does it disappear when under 20 mph, in gear or out, either coasting down to the lower speed, or while braking? Something that applying the brakes, do not affect it's volume or pitch?

I thought I should add that I do not have any brake shields front, or rear. Apparently they are often left off by FFR builders without any ill effect.
Is it possible something could become lodged in a caliper, and not vary in sound regardless of speed, or if brakes are applied? Anyone experience that before?
I keep thinking the sound is so similar to something like that, as it has happened to me on other vehicles. Usually simply reversing the vehicle has been the cure for that issue, as the object drops out.

It may be some sort of feedback from your sound system making the sound you hear. Try disconnecting it.

I think Mike's on the right track with either residual pressure, MC rod too long not letting the MC relieve, or heat affecting a brake line, one of which would be keeping your pads dragging just a bit. The key indicator is the excessive brake dust. I'd take it out for a drive, getting everything hot (hopefully making the mystery noise) then as soon as you pull in jack up each wheel and spin them manually to check for drag. You might also let it cool and see if the drag disappears which might point to heat from exhaust on a line or caliper? Just a thought....

I had a dream that you could use a piece of hose and route it to a location near the brake on a particular wheel and duct tape it so that the open end of the hose was pointed towards the caliper.....and while driving, you could put the other end of the hose near your ear to hear the ocean...or to hear some noise. This would theoretically tell you if the noise was brake-related.

Could it be a suspension part? Is it affected by road condition? Body mounts?

I used to get tons of brake dust on my wheels. So much that after just one night of crusiing the wheels had a gray tint. I was told to use ceramic pads. That reduced the dust greatly.

Have you looked at each pad? maybe something became embedded? I still think pressure is building. Maybe RSpears has an idea to try. Get it hot and noisy and jack it up testing each wheel.

Robot, maybe I can just duck tape that hose directly to my ear..lol

In retrospect I may have installed the pads without any anti-squeal compound applied to the back of them. I'm thinking I did, but now I am starting to wonder? :confused: Using it used to be standard procedure in older cars, but I don't see much mentioned of it anymore.

I'm just going to have jack it up again, and pull the pads off for a better idea if they are in fact the culprits or not. I'll let you know the results.
Better pads than a rear end failing!

If the pads don't solve your problem I'd look at the u- joints even though you say they are brand new. One bad needle bearing could be the culprit.

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Originally Posted by NTFDAY

If the pads don't solve your problem I'd look at the u- joints even though you say they are brand new. One bad needle bearing could be the culprit.

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Good point, that could definitely be another source of this weird sound. It has crossed my mind that could be the source. I greased the u joints after the sound first appeared, but it didn't seem to make any difference.

Not sure if grease would temporarily prevent the noise or not, if in fact it was a bad needle bearing? Any idea if that would make a difference?

I don't think grease would make a difference. I had one on a 91 Dakota that would howl mostly over 45 mph, but hardly made a squeak under 45

Just a thought, try the zinc grease and put a slight chamfer on the leading and trailing edge of the pads. If you have access to a hoist you could run it up With the wheels of the ground and see if the noise is in the drive train or not.

Has anyone metioned axel bearing, new bearings in the rear were more then likely the carrier bearings.

When i fitted the rear discs to my 67 i noticed the length of the bolts that hold the axle flange in place was an issue. If the tail of the bolts faced towards the inside of the disc they would just touch the inside of the disc when rotating. I turned the four axle flange bolts around and the clearance issue resolved itself. Just something to check. This may be only a problem with the kit i have.
Cheers
Al.

That's a good one something rubbing back there, it does not sound like a brake problem the sound is not changing when they are applied.. If brakes are dragging you will smell them cooking and feel the heat when you walk up on the wheel. Sound goes away at very low speed, low speed low load, sound from the rear. An axel bearing will do exactly that, I do like the long bolt possibility suggested above it would be worth checking out.

UPDATE
After several inspections to locate this mysterious noise, all of which failed to detect exactly what was causing it..it just suddenly stopped one day.. :3dSMILE: Ghost in the Machine I guess?

I've now driven a couple hundred miles, still quiet.. thankfully.


Appreciate all the help and suggestions.:)

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Originally Posted by Chev malibu

UPDATE
After several inspections to locate this mysterious noise, all of which failed to detect exactly what was causing it..it just suddenly stopped one day.. :3dSMILE: Ghost in the Machine I guess?

I've now driven a couple hundred miles, still quiet.. thankfully.


Appreciate all the help and suggestions.:)

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Sometimes the best solution for a low, unexplained noise is to turn up the radio. If it gets worse, it'll get louder...