Hi. I have a 2000 4WD Blazer. Can anyone help me identify a weird noise that has been driving me crazy for a while now?

When accelerating on part-throttle there is a strange noise that seems to be coming from somewhere under the hood. I can't identify if it's mechanical, hydraulic or what. The noise is not loud, and is not a knock, hum, squeak or rattle. The nearest thing I've heard it compared to is the sort of noise the beans in a coffee grinder make. Imagine someone using a coffee grinder in the next apartment and you have the sort of noise I mean.

The noise is not as noticable when the engine is cold and it seems to disappear when you accelerate hard. It is when the engine is under load, though, as I've tried revving the engine in Park and I can't hear it, but if I move into gear and pull away the noise is present. I thought it might be a transmission fault (torque converter??) but I've taken it to a transmission shop and they've driven it around and they say that the transmission seems to be okay.

The noise doesn't seem to be getting any worse, but it's bloody annoying and I find myself listening for it everytime I drive. The car also seems to lack a bit of power when the noise is present, but I don't know if this is just psychological. Any ideas anyone?

All the best
Lee

 

Mine is making a similar noise right now. The catalytic converter has a rattle, most noticeable when accelerate. A mechanic said the insides of these converters can crack or break into pieces that cause this noise. They also have a heat shield that can cause a similar noise. Don't know if thats your problem or not but might be something for you to check. Please let us know what you find.

 

Hi. Thanks for your suggestion. I'll check it out and let you know if I find anything.
Cheers
Lee

 

If the insides of the converter are breaking up you can hear the rattle if you bang on the converter with a rubber mallet.
You usually hear them rattle at an idle.

 

Yea, mine has a slight rattle occasionally while idling. When I pressed my foot on the exhaust outlet the rattling went away. That was another clue it was the catalytic converter. I like the "coffee grinder" description, pretty accurate!
My mechanic was surprised that it's failure hasn't set a code (Check engine light). He said it probably will eventually.

 

your gas milage will suffer too once it gets bad enough. resulting in a plugged cat

 

Hmmmm, that's good to know, thanks. It's on my "list" of things to get done.
Appreciate it!

 

If you replace it don't throw the old one away. You might be surprised at what recyclers will pay for them? Some will lowball you so call around.

 

What you describe sounds precisely like my S-10 did a few weeks ago. The sound was driving me nuts and seemed impossible to pinpoint. Finally I poked around a bit with my mechanic's stethoscope probe and finally found the problem.

Of all things it ended up being a bad PCV valve making the noise. I replaced the valve and the noise stopped immediately.

 

Hi. Thanks to everyone for their advice. Haven't managed to sort the noise yet, but it's given me some good ideas. Cheers. Lee