UNKNOWN TINNY NOISE ONLY WHEN BRAKING HARD [AND] MIN 1/2 tank gas
10-22-2017, 06:52 PM
#1
UNKNOWN TINNY NOISE ONLY WHEN BRAKING HARD [AND] MIN 1/2 tank gas
1992 Camaro Z28 4-speed auto
MECHANICS STUMPED
(SYMPTOM)
So around 6-7 months ago I started to experience a LOUD [embarrassing] tinny sound (Coming from the rear) when I would apply the brakes (hard or when coming to a full stop on a hill downwards) and coming to a complete stop.
I took the car for a drive to try and diagnose where it's coming from. I discovered the following:
- ONLY occurs when braking hard or on a hill going down and having to apply the brakes when coming to a stop
- Does NOT happen when applying emergency brakes when driving
- Does NOT happen on bumps.. just braking
- Does NOT happen when in REVERSE.. ONLY FORWARD.
- I tried in all gears including neutral but happens in all.
- I tried shaking the car, pushing on the shocks.. can't reproduce, ONLY while going forward and apply brakes.
It sounds like a tinny sound.. a vibration.. Placed camera outside of car and drove some speed.. perhaps 20-30km and hit brakes but discovered it was MUCH MUCH LOUDER when the camera was IN THE TRUNK.. So I suspect it is under the trunk..
TANK GAS SHIELD?
VIDEO OUTSIDE CAR: AUDIO INSIDE TRUNK:
(STORY: DETAILED)
At first I assumed it was my brakes and so I took the car back to the dealer and they told me that the insulators on my 2 year old brake pads on the rear came loose and 1 was literally shattered into little pieces. NO WARRANTY considering they did it 2 years ago and only 2,500 km on car since then. $336 later to replace rear brake pads..
It was fine for a few days and then it started up again. That proved it was nothing to do with the brake pads. Took it back to the dealer and they said they couldn't hear anything. We went on a test drive and it didn't do it! Took the car back and it seemed fine for another few days and then once again it started up again. Back to the dealer and once again STOPPED doing it..
GAVE UP and decided to just see what would happen if I continued to drive.. The next day it was gone.. and once again.. 3-4 days later it would come back..
COULD NOT figure out what was going on.. UNTIL I realized a PATTERN..
COINCIDENTALLY when I filled up the gas tank, the sound disappeared.. When it came back it was at 1/2 tank of gas.. Then I realized that I filled up the tank before taking it to the dealer each time where they would claim not to hear it. I realized the fuel tank was a SYMPTOM! The moment it got to 1/2 tank then the sound would start up and would get louder as the tank emptied out.
Also I can coast at a bit of speed and hit the brakes hard where it makes the noise, let go and the noise will continue with the brakes off for 1 second later after releasing the brake pedal so it's a vibration..
(WHAT THE DEALER SUSPECTED)
With this in mind, I took it back to the dealer with the gas low and they claimed the following to fix it: ($1000+ Canadian)
- They suspect that the FUEL PUMP was on its way out and as the gas gets lower in the tank that the pump would have to work harder. But they would not know for sure if it's that until they remove it.. which means DROPPING the exhaust, DROPPING the suspension, Empying out the gas in the tank, DROPPING the tank, and replacing the fuel pump.. and it MIGHT fix it.. (They suggested to replace the pump either way since it's convenient at that time).
Now Originally that made sense and I was going to do that because obviously the gas in the tank seems to be the culprit some how but then I thought about it more.. If it was just the pump working harder then why is it that it ONLY occurs when the brakes are applied hard and coming to stop... You would think that it would just make that noise all the time.. Does not appear to be related to the angle of the car because the car can be a REAL STEEP HILL and it doesn't do it until again the brakes are applied coming to a stop.. It's been suggested that it's because when you brake that the gas forces to the end of the tank with momentum but if that were the case then I would think it would do it when coasting down a STEEP HILL or UP a steep hill with the gas would be definitely up the back/front side of the tank..
I took the car to (2) other mechanics and they are stumped.. The dealer just wants me to pay $1000+ for the fuel pump replacement and it might not even fix it..
(WHAT I SUSPECT: YOUR THOUGHTS??)
I'm trying conclude what it can be and how each of the parts are related.. I Do NOT feel the fuel pump has anything to do with it.. I don't see how it can when it's only happening when braking hard with a MIN 1/2 tank of gas. So the brake has something to do with it.. I am thinking 1 or more of 3 ideas:
1) The gas when 1/2 tank is not as heavy in the tank and that it's enough to rub on something.. But how the brakes are involved?
2) The brake line is close to the tank and perhaps touching the tank when the gas is not as heavy in the tank and it's enough to move the tank to touch the line?
3) The brake line is touching the tank no matter what but when the tank is low on gas that it's resonating the vibration thru the metal tank??
Seems could be it but where does the VIBRATION come into play is what baffles me.. It can be a perfectly straight, and smooth road.. Is there there vibration in the brake lines when the brakes are applied normally??
As of right now, I only get around 3-4 days out of my gas (80-100km) because once I hit the 1/2 mark (ON THE DOT), I have to go replenish the gas because I have to deal with this embarrassing noise..
MECHANICS STUMPED
(SYMPTOM)
So around 6-7 months ago I started to experience a LOUD [embarrassing] tinny sound (Coming from the rear) when I would apply the brakes (hard or when coming to a full stop on a hill downwards) and coming to a complete stop.
I took the car for a drive to try and diagnose where it's coming from. I discovered the following:
- ONLY occurs when braking hard or on a hill going down and having to apply the brakes when coming to a stop
- Does NOT happen when applying emergency brakes when driving
- Does NOT happen on bumps.. just braking
- Does NOT happen when in REVERSE.. ONLY FORWARD.
- I tried in all gears including neutral but happens in all.
- I tried shaking the car, pushing on the shocks.. can't reproduce, ONLY while going forward and apply brakes.
It sounds like a tinny sound.. a vibration.. Placed camera outside of car and drove some speed.. perhaps 20-30km and hit brakes but discovered it was MUCH MUCH LOUDER when the camera was IN THE TRUNK.. So I suspect it is under the trunk..
TANK GAS SHIELD?
VIDEO OUTSIDE CAR:
(STORY: DETAILED)
At first I assumed it was my brakes and so I took the car back to the dealer and they told me that the insulators on my 2 year old brake pads on the rear came loose and 1 was literally shattered into little pieces. NO WARRANTY considering they did it 2 years ago and only 2,500 km on car since then. $336 later to replace rear brake pads..
It was fine for a few days and then it started up again. That proved it was nothing to do with the brake pads. Took it back to the dealer and they said they couldn't hear anything. We went on a test drive and it didn't do it! Took the car back and it seemed fine for another few days and then once again it started up again. Back to the dealer and once again STOPPED doing it..
GAVE UP and decided to just see what would happen if I continued to drive.. The next day it was gone.. and once again.. 3-4 days later it would come back..
COULD NOT figure out what was going on.. UNTIL I realized a PATTERN..
COINCIDENTALLY when I filled up the gas tank, the sound disappeared.. When it came back it was at 1/2 tank of gas.. Then I realized that I filled up the tank before taking it to the dealer each time where they would claim not to hear it. I realized the fuel tank was a SYMPTOM! The moment it got to 1/2 tank then the sound would start up and would get louder as the tank emptied out.
Also I can coast at a bit of speed and hit the brakes hard where it makes the noise, let go and the noise will continue with the brakes off for 1 second later after releasing the brake pedal so it's a vibration..
(WHAT THE DEALER SUSPECTED)
With this in mind, I took it back to the dealer with the gas low and they claimed the following to fix it: ($1000+ Canadian)
- They suspect that the FUEL PUMP was on its way out and as the gas gets lower in the tank that the pump would have to work harder. But they would not know for sure if it's that until they remove it.. which means DROPPING the exhaust, DROPPING the suspension, Empying out the gas in the tank, DROPPING the tank, and replacing the fuel pump.. and it MIGHT fix it.. (They suggested to replace the pump either way since it's convenient at that time).
Now Originally that made sense and I was going to do that because obviously the gas in the tank seems to be the culprit some how but then I thought about it more.. If it was just the pump working harder then why is it that it ONLY occurs when the brakes are applied hard and coming to stop... You would think that it would just make that noise all the time.. Does not appear to be related to the angle of the car because the car can be a REAL STEEP HILL and it doesn't do it until again the brakes are applied coming to a stop.. It's been suggested that it's because when you brake that the gas forces to the end of the tank with momentum but if that were the case then I would think it would do it when coasting down a STEEP HILL or UP a steep hill with the gas would be definitely up the back/front side of the tank..
I took the car to (2) other mechanics and they are stumped.. The dealer just wants me to pay $1000+ for the fuel pump replacement and it might not even fix it..
(WHAT I SUSPECT: YOUR THOUGHTS??)
I'm trying conclude what it can be and how each of the parts are related.. I Do NOT feel the fuel pump has anything to do with it.. I don't see how it can when it's only happening when braking hard with a MIN 1/2 tank of gas. So the brake has something to do with it.. I am thinking 1 or more of 3 ideas:
1) The gas when 1/2 tank is not as heavy in the tank and that it's enough to rub on something.. But how the brakes are involved?
2) The brake line is close to the tank and perhaps touching the tank when the gas is not as heavy in the tank and it's enough to move the tank to touch the line?
3) The brake line is touching the tank no matter what but when the tank is low on gas that it's resonating the vibration thru the metal tank??
Seems could be it but where does the VIBRATION come into play is what baffles me.. It can be a perfectly straight, and smooth road.. Is there there vibration in the brake lines when the brakes are applied normally??
As of right now, I only get around 3-4 days out of my gas (80-100km) because once I hit the 1/2 mark (ON THE DOT), I have to go replenish the gas because I have to deal with this embarrassing noise..
Last edited by camarosource; 10-22-2017 at 06:58 PM.
10-22-2017, 07:52 PM
#2
Re: UNKNOWN TINNY NOISE ONLY WHEN BRAKING HARD [AND] MIN 1/2 tank gas
Sounds about like brake groaning. Assuming your car came with PBR rears, they're kind of known for groaning. GM even added dampers in mid-late 91 that continued through the 4th gens. It'd be worth checking the dampers to be sure they haven't come loose or something goofy.
There are a few heat shields back there. There's one over the intermediate pipe where it comes over the axle, then the one above the muffler. The one for the intermediate pipe has a rubber bumper on it, IIRC. It'd be fairly easy to get under the car and check the shields for loose anchor points. That would be a good time to check out all the ebrake cable mountings and guides.
There are a few heat shields back there. There's one over the intermediate pipe where it comes over the axle, then the one above the muffler. The one for the intermediate pipe has a rubber bumper on it, IIRC. It'd be fairly easy to get under the car and check the shields for loose anchor points. That would be a good time to check out all the ebrake cable mountings and guides.
10-22-2017, 08:04 PM
#3
Re: UNKNOWN TINNY NOISE ONLY WHEN BRAKING HARD [AND] MIN 1/2 tank gas
Sounds about like brake groaning. Assuming your car came with PBR rears, they're kind of known for groaning. GM even added dampers in mid-late 91 that continued through the 4th gens. It'd be worth checking the dampers to be sure they haven't come loose or something goofy.
There are a few heat shields back there. There's one over the intermediate pipe where it comes over the axle, then the one above the muffler. The one for the intermediate pipe has a rubber bumper on it, IIRC. It'd be fairly easy to get under the car and check the shields for loose anchor points. That would be a good time to check out all the ebrake cable mountings and guides.
There are a few heat shields back there. There's one over the intermediate pipe where it comes over the axle, then the one above the muffler. The one for the intermediate pipe has a rubber bumper on it, IIRC. It'd be fairly easy to get under the car and check the shields for loose anchor points. That would be a good time to check out all the ebrake cable mountings and guides.
Do you have any pics of where those dampeners are? Can I see by crawling under the car or need to least jack the car up to see?
If it were a heat shield, I'm not understanding how the brakes could control the sound... ?
Thanks
10-22-2017, 10:54 PM
#4
Re: UNKNOWN TINNY NOISE ONLY WHEN BRAKING HARD [AND] MIN 1/2 tank gas
82-88 rear discs use cast iron calipers designed by Delco Moraine, they're so bad, that GM outsourced the 89-92 rear disc calipers to PBR (Paton Brake Replacements) an Australian brake company. The PBRs are easy to spot since they're aluminum, and generally have the "PBR" cast right on the caliper.
The dampers look like a cast iron hockey puck, hanging in the wind.
Since what you're likely experiencing is a harmonic vibration, any number of factors could play into it. The part that is making the noise might not be where the vibration originates, it's just where the tuning fork effect happens.
The dampers look like a cast iron hockey puck, hanging in the wind.
Since what you're likely experiencing is a harmonic vibration, any number of factors could play into it. The part that is making the noise might not be where the vibration originates, it's just where the tuning fork effect happens.
