Scraping noise, after being in PARK

Hey guys,

I just bought a 2004 Buick Rendezvous with 84,000 miles. I got it checked out, mechanic said it was ok. I’m getting ready to drive across the country with it, towing all my things in a small trailer.

I’ve noticed an unusual noise recently though, that I don’t know how to diagnose.

After the Buick is parked for the night, when I put it in drive, somewhere within the first 30 feet of rolling, there is a scraping car under the car. It sounds like the bottom of the car is scraping on something for just a second or two, and I can feel the vibration translate down the gas pedal.

I don’t think it’s sticking brakes or anything like that. It only makes this noise after it’s been parked for a while. Not after a red light, or if I’m just running into the store for a minute. It does seem to be happening more frequently though.

Any help is appreciated!

Is it humid where you are?

If so, the rotors may be forming rust on the surfaces as the vehicle sits overnight.

https://www.autoguide.com/auto-news/2019/08/rust-on-brakes-does-it-matter-.html

Tester

Hi Tester,

That would make sense to me if the scraping started as soon as I started driving, then gradually wore off as I used the brakes. But the scraping starts after rolling for about 20 feet, and only lasts for 2 seconds max, and never comes back until I put it in park again. It also makes the noise when the brakes aren’t applied.

It might be an ABS self test. I had a 2005 Honda Accord that did that, but only moving forward. No noise after startup and backing 50 feel out of the driveway, but then the noise happened shortly after moving forward.

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That’s interesting. I think it makes the noise in reverse but I’ll double check…

The ABS isn’t working on this car because one of the ABS sensors is disconnected. Just vanilla brakes. I wonder if the self-test would still engage

I would also guess it is the ABS unit. I would expect the vehicle to continue the self-test even if the sensors are disconnected. Is the ABS unit itself disconnected? Are you getting an ABS CEL?

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Well, you bought it. So I will just go with it.

It’s just one of the sensors that’s disconnected. The CEL is on for the ABS.

Verified today: it does make the sound when driving in reverse.

Going to give the mechanic a call tomorrow. He initially told me the car was in sound mechanical shape. I’ll let you guys know if anything conclusive comes from talking to him

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