Rattle underneath my car?

June 26, 2009 12:26 PM

Is my car safe to drive?

I have a '02 Kia Rio (2WD automatic if it matters) which has been faithful to me the past two years. Nearly all of the maintence required items (brakes, tires, etc) were either replaced when I bought it two years ago or after. Besides the fact that my car hums a bit louder than others when the AC is on, I'd say it has always felt/sounded like a normal car... until about two weeks ago.

I went on a small road trip two weeks ago, and there I had a problem where my car would not accelerate as quickly as usual. The last day of the trip I put in in reverse, and when I stepped on the gas it outright stalled. I drove home, talked to a mechanic about it, and he suggested it might've been something that just happened because I was on a slope or a myraid of other reasons, but if I had the problem again to give him a call. I haven't had the problem again, but within the past week I have developed a rattle which may or may not be related. It sounds like it's coming from underneath my car, possibly in the back passenger side area. It reminds me mostly of a wobbly metal fan slowing down after you turn it off, and it happens when breaking and when the car is in reverse (I'm beginning to attribute it to the car going at a very slow speed).

Now, I know that no one can see my car, but I'm hoping that I can get some generalized advice. I'm getting ready to take a road trip this weekend with some friends. I have noticed no difference in the driving (it now accelerates just fine, and otherwise sounds and vibrates as normal) of my car besides that. The previously mentioned mechanic took a 4-day weekend and is unreachable for advice. Since I will have my friends with me, however, I don't want to strand them in the middle of Chicago. Has anyone had any similar experiences with their car that they can hint at what I might get looked at? Also, if there are any car aficionados or mechanics out there, do you know if it would be safe to drive several hours?

posted by semp to travel & transportation (11 comments total)

The Rio is a front-wheel drive vehicle, which leads me to wonder what you are really hearing from "the back passenger side area".

If the sound is really coming from that area, I'd start wondering about rear axle or even brakes.
posted by Kickstart70 at 12:32 PM on June 26

The rattle is probably your exhaust. You should be fine. Don't worry - be happy!
posted by torquemaniac at 12:33 PM on June 26

A rattle from that area is most likely an exhaust heat shield.
posted by sanka at 12:37 PM on June 26

Seconding exhaust heat shield. I had exactly the same problem with an old Honda; when stopped at a light, I'd hear the vibration whenever I applied my brakes. The problem wasn't the brakes, but the slighlty increased engine load, causing the vibration.
posted by MrMoonPie at 12:42 PM on June 26

This sounds like a loose exhaust heat shield or pipe; a broken pipe could account for the louder-than-normal engine note as well as reduced power (due to loss of back pressure). It should be safe to drive but be weary of exhaust fumes coming into the car when you aren't moving.
posted by bizwank at 12:45 PM on June 26

nthing the loose heat shield. Odds are you're fine.
posted by jon1270 at 12:50 PM on June 26

A late model automatic trans car should never stall. Is your check engine light on?
posted by Jon-o at 1:07 PM on June 26

Well, I'd say heat shield too...except, you say that you hear it when you are braking or in reverse. A heat shield rattle would not be so specific. In fact, you'd primarily hear when accelerating forward, or upon first starting the car.
posted by Thorzdad at 1:13 PM on June 26

I am going to say that the rattle & the stalling are unrelated. Too bad your trusted mech. is not around. Needs to go up on a lift & find what is rattling. As for the stalling maybe gas related (change the filters (air too), add some gasdry and/or injector cleaner to the gas). Or possible intermittent fuel pump or ignition failure. Hard to diagnose intermittent issues.
IANAM
posted by patnok at 1:30 PM on June 26

"... it happens when breaking and when the car is in reverse (I'm beginning to attribute it to the car going at a very slow speed). ..."

A sticking or pulling rear brake could account for performance issues, and noises you describe.

The Kia Rio has drum rear brakes as standard equipment, equipped with the standard type of brake self-adjusters that have been used since the early '30s. If you notice the rattle mostly at low speed, or when braking it is possible that your rear brakes are simply out of adjustment, or that you've broken a shoe return spring, shoe pivot pin, or other bit of brake hardware (due to age, heat and general use).

Adjusting self-adjusting brakes is as simple as backing the car up when the brakes are cool, and coming to a complete stop, a few times in a row. The self-adjuster mechanism will take up any slack in the shoe-to-drum clearance of the rear brakes, by converting rotational energy from the wheel, to ratchet turns of the self-adjuster. Normally, people don't actually think about this, as particularly rear brake shoes wear very slowly, and the usual amount of adjustment that occurs as a result of backing up out of parking spaces is enough to keep the brakes adjusted. But, it doesn't hurt to explicitly do the adjustment by the backup-and-stop method, either. Just don't do it more than 2 or 3 times in a row, so as to keep from adjusting to "heated drum" clearances, which will have your brake dragging in normal driving, until it is worn down, causing overheating of the drum and shoe linings.

However, if you've broken a drum return spring, or have other faulty hardware in your rear brakes, the only way to discover it is to pull the wheels and have a look. Fortunately, any competent brake shop can do this in about 15 minutes, even on a Saturday morning. Many brake service specialty chains will even do an inspection for free (but don't be surprised if they find you "need" brake work, as a result, on a vehicle of this age. A seven year old car generally does need brake work.)
posted by paulsc at 1:45 PM on June 26 [2 favorites]

My vote is some sort of failure with the emergency brake, along the lines of paulsc's comment.


The rattle is probably your exhaust. You should be fine. Don't worry - be happy!

A loose exhaust system will rattle until eventually something breaks. Certainly won't kill you or the car (unless CO starts seeping into the car), but not something to ignore either. Broken exhaust pipe: $. Broken catalytic converter due to vibrating exhaust: $$$.
posted by Big_B at 2:32 PM on June 26