Brake Rotor Warp
gnrboyd
02-08-2009, 12:25 PM
Car: 2002 Cavalier LS Sport
In a previous post, I explained an issue I had on an ABS brake sensor wiring harness. (search my user name if you care to read the novel) Related to that, I have a question about the brakes.
Here's the semi-short version:
My front left ABS sensor plug was damaged and caused the ABS, trac off, and service lights to come on in my dash. (diagnosed by a shop) I had to come back later for them to make the repairs. Before going back to the shop, I stopped and washed the car at a car wash. On the way to the shop, I noticed a thumping noise (from front of car) when I was coasting. The car was not doing this prior to washing the car. It seemed to go away when I accelerated. I also noticed a little pulsing while braking like the wheel was out of round.
I told the mechanic about it when I got there and he said he thought I had a good amount of brake pad left and that the rotors "might" be warped.
The mechanic fixed the ABS plug and the lights on the dash went out. I only drove it a few miles but didn't get to very high speeds that would allow me to test the coasting at medium to high speeds where the problem was noticeable. (I was taking the car to my daughter's school which is a short distance from the auto shop. From there she needed it to go elsewhere.)
My daughter drove the car (it's hers) home and also the next day and said she didn't notice any noise like I explained. (However, she is 17 and may not have heard it over the radio.)
I did some additional research and found that spraying cold water on a hot rotor could cause it to warp. The car's wheels are alloy and much of the rotor is visible and would be easy to spray while washing the car. My first conclusion is that I must have warped the rotors by washing the car with hot rotors.
I went and bought new rotors and pads. (using another car) I test drove my daughter's car before changing the brakes today and I didn't notice the noise. (There was one time during my 20 minute drive that I thought I heard it a little but then again I may have been trying to hear it and tricked my ears.) It still has a very slight out of round feeling also when slowly coming to a stop.
I'm now wondering what could have happened. I have a couple of theories but I'm no mechanic so I may be way off.
1. Is it possible to warp the rotors using water on a hot rotor and have the rotor return it's normal shape over the next few hours? Is that possible or is that just wishful thinking?
2. The two variables that might play into this are that the rotors were wet and the ABS speed sensor wasn't functioning properly due to a damaged wiring harness. Could the computer have gotten confused and caused the pulsing noise I was hearing?
What are your thoughts on 1 and 2 above? (Other theories welcome also.)
The brakes and rotors were changed about 35,000 miles ago. They were changed by a shop while the previous owner had the car so I don't know what quality of parts they used. Since the mechanic said we had plenty of pad left, my gut tells me to return the parts and keep an eye on them to see if the problem returns. Then again, the pads and rotors were only about 125.00 (ceramic pads / 2 year rotors) so I wouldn't be investing a ton on money in replacing them. But we also may sell the car in the next year or so and get something better so no sense in putting money in something we may not keep.
I appreciate your thoughts on all of the above. Thanks
In a previous post, I explained an issue I had on an ABS brake sensor wiring harness. (search my user name if you care to read the novel) Related to that, I have a question about the brakes.
Here's the semi-short version:
My front left ABS sensor plug was damaged and caused the ABS, trac off, and service lights to come on in my dash. (diagnosed by a shop) I had to come back later for them to make the repairs. Before going back to the shop, I stopped and washed the car at a car wash. On the way to the shop, I noticed a thumping noise (from front of car) when I was coasting. The car was not doing this prior to washing the car. It seemed to go away when I accelerated. I also noticed a little pulsing while braking like the wheel was out of round.
I told the mechanic about it when I got there and he said he thought I had a good amount of brake pad left and that the rotors "might" be warped.
The mechanic fixed the ABS plug and the lights on the dash went out. I only drove it a few miles but didn't get to very high speeds that would allow me to test the coasting at medium to high speeds where the problem was noticeable. (I was taking the car to my daughter's school which is a short distance from the auto shop. From there she needed it to go elsewhere.)
My daughter drove the car (it's hers) home and also the next day and said she didn't notice any noise like I explained. (However, she is 17 and may not have heard it over the radio.)
I did some additional research and found that spraying cold water on a hot rotor could cause it to warp. The car's wheels are alloy and much of the rotor is visible and would be easy to spray while washing the car. My first conclusion is that I must have warped the rotors by washing the car with hot rotors.
I went and bought new rotors and pads. (using another car) I test drove my daughter's car before changing the brakes today and I didn't notice the noise. (There was one time during my 20 minute drive that I thought I heard it a little but then again I may have been trying to hear it and tricked my ears.) It still has a very slight out of round feeling also when slowly coming to a stop.
I'm now wondering what could have happened. I have a couple of theories but I'm no mechanic so I may be way off.
1. Is it possible to warp the rotors using water on a hot rotor and have the rotor return it's normal shape over the next few hours? Is that possible or is that just wishful thinking?
2. The two variables that might play into this are that the rotors were wet and the ABS speed sensor wasn't functioning properly due to a damaged wiring harness. Could the computer have gotten confused and caused the pulsing noise I was hearing?
What are your thoughts on 1 and 2 above? (Other theories welcome also.)
The brakes and rotors were changed about 35,000 miles ago. They were changed by a shop while the previous owner had the car so I don't know what quality of parts they used. Since the mechanic said we had plenty of pad left, my gut tells me to return the parts and keep an eye on them to see if the problem returns. Then again, the pads and rotors were only about 125.00 (ceramic pads / 2 year rotors) so I wouldn't be investing a ton on money in replacing them. But we also may sell the car in the next year or so and get something better so no sense in putting money in something we may not keep.
I appreciate your thoughts on all of the above. Thanks
J-Ri
02-11-2009, 05:31 PM
1- Possible to warp them if they were VERY hot... not possible for them to go back to normal if they did warp. While offroading, I've had the brakes so hot on my truck that I could smell them and then went through a creek and no warping (but they're about 5x thicker than on a cavalier)
3- It's good now, right? :wink:
3- It's good now, right? :wink:
gnrboyd
02-14-2009, 12:10 PM
3. We have not noticed the thumping noise all week so I guess the brake rotors were not the problem. ??
Since the noice occured when the wire to the ABS connector was damaged, do you think it is possible that this is where the noise was coming from. It was immediately noticable right after the car wash so I think water was a variable. I'd still really like to know what happened even though the noise seems to have gone away.
Thanks
Since the noice occured when the wire to the ABS connector was damaged, do you think it is possible that this is where the noise was coming from. It was immediately noticable right after the car wash so I think water was a variable. I'd still really like to know what happened even though the noise seems to have gone away.
Thanks
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