Help diagnosing scraping noise

[600rob]

Back ground: My 2002 mk1 yaris had developed a two different noises over the past few months as follows:

1. A whirring/droning noise on the front offside area that increased with vehicle speed. Most noisy at 50+ mph. Also more noticeable when turning to the left.

2. (What i though was) a sort of chugging sound (almost like a steam train) coming from the engine bay area. that also increased in speed when the vehicle was in motion.

My initial diagnosis was that sound 1 was a bad bearing on the front offside wheel and sound 2 was probably an exhaust leak, possibly from the manifold.

I've replaced the bearing and sound 1 has been eliminated.

After doing fixing the bearing, whats become more apparent after being able to listen to sound 2 in isolation is that its actually more of a scraping sound which I can now describe in more detail as follows.

Its a scraping/grinding sound that comes from the engine bay area. No discernible difference between near side and off side.

The noise is audible when the vehicle is moving in all gears and increases with vehicle speed and is more audible when applying gas to the accelerator.

If i disengage the clutch and let the vehicle coast, the noise quietens a little but can still be heard. Same goes for putting it in neutral and coasting.

There is no difference in the noise when steering left to right.

The noise does not occur when the car is stationary at idle or when revving the engine

Ive had the car back on the stands to check both the new bearing and the old one on the near side. I cant hear or feel any grittiness and there is no play in either of the bearings. 

Ive also double checked that neither of my front brake discs are rubbing against the hub dust shield and that there is no debris stuck between my pads and discs 

spinning the front wheels with when the car is on the stands does not make the sound either.

Has anyone got any suggestions as to what it could be and where i should be looking next?

 

 

 

 

[Bernard Foy]

2 minutes ago, 600rob said:

Back ground: My 2002 mk1 yaris had developed a two different noises over the past few months as follows:

1. A whirring/droning noise on the front offside area that increased with vehicle speed. Most noisy at 50+ mph. Also more noticeable when turning to the left.

2. (What i though was) a sort of chugging sound (almost like a steam train) coming from the engine bay area. that also increased in speed when the vehicle was in motion.

My initial diagnosis was that sound 1 was a bad bearing on the front offside wheel and sound 2 was probably an exhaust leak, possibly from the manifold.

I've replaced the bearing and sound 1 has been eliminated.

After doing fixing the bearing, whats become more apparent after being able to listen to sound 2 in isolation is that its actually more of a scraping sound which I can now describe in more detail as follows.

Its a scraping/grinding sound that comes from the engine bay area. No discernible difference between near side and off side.

The noise is audible when the vehicle is moving in all gears and increases with vehicle speed and is more audible when applying gas to the accelerator.

If i disengage the clutch and let the vehicle coast, the noise quietens a little but can still be heard. Same goes for putting it in neutral and coasting.

There is no difference in the noise when steering left to right.

The noise does not occur when the car is stationary at idle or when revving the engine

Ive had the car back on the stands to check both the new bearing and the old one on the near side. I cant hear or feel any grittiness and there is no play in either of the bearings. 

Ive also double checked that neither of my front brake discs are rubbing against the hub dust shield and that there is no debris stuck between my pads and discs 

spinning the front wheels with when the car is on the stands does not make the sound either.

Has anyone got any suggestions as to what it could be and where i should be looking next?

 

 

 

 

Is the alternator suspect, it might be coming from there.

[600rob]

I've not had any suspect behavior from the alternator but can take a look later and report back.

If it was a bad alternator bearing, wouldn't that type of thing be noticeable at idle/stationary? 

[Bomber209]

Hi, put a long thin rod onto the Alternator, and to your ear (with engine running) if there's no noise then your problem could be the Clutch Thrust Bearing. Good Luck.

[600rob]

21 minutes ago, Bomber209 said:

Hi, put a long thin rod onto the Alternator, and to your ear (with engine running) if there's no noise then your problem could be the Clutch Thrust Bearing. Good Luck.

Cheers. Was going to this using the screwdriver 'stethoscope' trick but a longer rod will be easier for sure. 

Had a new clutch put in a few years back, not sure if that included the thrust bearing though. Anyway l'll check out the alternator first

[DerekHa]

Hi Rob,

From your descrition, after the bad wheel bearing has been replaced, my inclination is that your noise is related to wheel ration as the noise increases and decreases with road speed.

A failing alternator bearing would definately cause noise but think you would hear that when stationary with engine running.

Some years ago I had a Mazda 3 that suddenly developed a horrible scrapping, grinding noise, after a 20 mile journey on the motorway. Coming from the front end when the car was being driven, it had started just as I drove onto a gravelled area. No noise at all when stationary. Drove home very carefully and called in on a friendly mechanic on the way, who gave me some advise.

Took his advise and checked each front disc and the back plate. Forget which side it was now but right in there was a fair sized piece of road grit, must have got picked up and then somehow got between the back plate and brake disc, was well and truely jammed in there quite low down close the hub. Got it shifted with something long and thin to get in between the back plate and the disc. No sign of any real damage on the brake disc and it was now back to normal.

I was convinced a front wheel was about to fall off it was that bad.

 

[paul9]

Try pressing and releasing the clutch pedal both when stationary in neutral, and rolling in gear to see if the noise could be related to the thrust bearing.

[600rob]

On 11/9/2022 at 1:31 AM, paul9 said:

Try pressing and releasing the clutch pedal both when stationary in neutral, and rolling in gear to see if the noise could be related to the thrust bearing.

update: Ive been out and about in the car a few times now and tried the above.

While stationary there is no noise when pressing and releasing the clutch in neutral or in any gear.

when the car is rolling in neutral the scraping noise can be heard faintly. depressing and releasing the clutch doenst have any affect on the noise

while rolling in gear, the noise is fairly loud ( increases with speed)  depressing and holding the clutch down seems to quieten down the noise somewhat although its still audible. when i release the clutch the  noise returns to its original louder state. No real difference between gears and no difficulty changing gears. Had a new clutch fitted a few years ago (probably less than 20k miles ago) cant remeber if that included the release bearing

 

[DerekHa]

Another cause comes to mind as this occures with the car in motion.

Try checking the disc brake back plates. With age the back plates corrode and can eventually come into contact with the brake disc rims which will be corroded unless the disks have been replaced. There could be a high point on the rim of the disc that just scraps against one of the back plates. Equally if you have rear drums they could be scraping the backing plate in the same manner.

[600rob]

Yea i did check the back plates and all seemed okay, i even bent them back out of the way just to be sure.

Will probably jack the vehicle up again tomorrow and have another look