CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Rattling noise above 2000 RPM - 1994 Saturn SL2

When I accelerate above 2000 RPM, a rattling noise (almost like when a kettle is sitting atop the stove and the water is boiling) comes from under the hood. The sound does not get louder as I accelerate above 2000 RPM (i.e. the sound is constant as long as the engine is above 2000 RPM). I took it to the mechanic, he said that the serpentine belt assembly needed tightening but that did nothing to eliminate the sound. I’m concerned it might be my timing chain. As soon as the engine decelerates below 2000 RPM (say when I put the car in neutral) the noise disappears. It is a 1994 Saturn SL2, manual transmission.

Any thoughts would be greatly appreciated!

Most likely a loose heat shield somewhere on the exhaust system. They can make a lot of strange noises due to resonant vibration at certain rpm.

Unless you make a habit of parking on overgrown dry grass, break off the heat shield and drive on.

BTW, never mention something like a timing chain problem to your mechanic unless you REALLY trust him. A fishing expedition like that is big $$$ and most likely not the problem. On a 1994 Saturn, probably more cost-effective to junk the car than fix something like that.

In other words, talk to your mechanic about symptoms, not possible diagnoses or fixes. Let him do the investigation.

Withe the engine running, pop the hood, slowly accelerate the engine (this '94 should still have a cable with linkage), and see if you can get an idea where the sound is originating from. A “mechanic’s stethescope” (about $10) would help, as you can tuoch variouys components with it as the engine runs and see which one is the culprit.

And mleich might be right. It might be a loose heat shield resonating. If it is, you can fix it with a $2 oversize hose clamp from the hardware store.

I have to agree with mleich except for the part about talking with your mechanic. Talk to another mechanic. That part about tightening the serpentine belt tells me that this is not a guy to do business with.

If the vehicle has over 100,000 miles on it the noise could be from the timing chain assembly. The timing chain assembly comprises of the timing chain, the plastic timing chain guide, and the plastic timing chain tensioner. So the timing chain itself might not be worn out, but the plastic guide and tensioner are worn out causing the noise.

Tester

It could be the timing chain, but I think @mleich is probably spot on – it’s the exhaust shield (probably the one above the cat) rattling. Any good mechanic can prove or disprove this as the cause, easy as pie.

I had this same problem on my pick up. Right around the 2,000 rpm mark I would here this rattly, vibration sound. Once the engine was above or below 2,000 rpm’s the noise would go away. Turns out the outer shielding on my muffler was rotting off. I cut the remaining shield off and it temporarily solved the problem. About a year later I changed the muffler and killed the noise forever. I would look at heat sheilding around the exhaust system and you might find the problem there. Noises can be transmitted throughout the exhaust system and what you may be hearing under the hood could be starting at the heat shield around your catalytic converter.

I think the muffler suggestions are spot on. I had the exact same thing happen with an old GMC truck once; the muffler would start “rattling” at highway speeds, right around 2000 RPM. If your muffler’s never been replaced, this might be the time. Good luck.