Need help determining a noise.

[86blazerk5]

Hey guys, I have been have this noise lately that souds as if it might be a heat sheild or something. But I am affraid it might be something more. It does not make the noise when I am in park or nuetral. I really only makes the noise when the truck is going up a hill or is under some kind of load. However, it dosnt do it everytime I pull a hill. Its usually most noticable when i am going about 30 to 40 miles an hour. I think it is most common to 2nd gear. But I could be wrong. My oild preeusure is gine, and my engin temp is good. Kinda souds like a rattle but it is verry even in vibration. Iy also seems to be coming from below me or right in front of me while driving. I know this is nt really much to go on, I am just looking for thing s to check out. Another note, my gas milage has been worse lately. Could be unrelated. Thanks,
Ike

 

[ChevBlazin]

The catalytic converter on my 84 s-10 blazer would some times rattle and make noise, I just lived with it. It also did it under a load, like pulling a trailer. I guess if the cat is plugged or something it could make the gas milage worse??

 

[86blazerk5]

I am thinking that there is a good chance that that is where its coming from. The cat or the heat sheild above the cat. I am wondering if anyone has some other sugestions as to what it could be also.
Thanks,
Ike

 

[Twiz]

Tuff call. (gotta be there)

Try Power brakeing.
With the parking brake engaged fully, put the trans in drive with your left foot firmly on the standered-brake pedal. Raise engine RPM slowly with your right foot, until you can duplicate the noise you are hearing. Try to find the "sweet" spot.

Then carefully have someone listen out-side the vehical to try to locate the noise.
Obviousely, Haveing someone out-side of the vehical, while it is being power-braked is dangerouse, be carefull.

 

[90K5]

Check your pulleys. Mine would make rattling noises sometimes under a load, and it turned out I had bad bearings on the idler and tensioner pulleys. While the engien is running, get a screwdriver long enough to use as a sthetescope and put it near the pulleys. If one of them is bad you will be able to tell, it will sound real bad.

 

[UseYourBlinker]

Might be your EFE valve ....If you are running one. (Here in Cali you need it to pass smog). Mine would form and exhaust leak,and make a rattling noise.. Especially in 2nd gear!

 

[86blazerk5]

Diagnosed it... after reading your posts and thinking more about the noise and where it apears to be coming from, I determined it was the propbaly the cat heat sheid. So I got under the truck and tugged on it, but it was tight. So I figureed it was the cat, the cat isnt in good shap, but certainly didnt look to be the culprit either. Well, I belive to have a broken hanger somwhere as well becuase my pipe moves to much, so I started to move the pipe and saw he the u bolt in from of that cat was just about rustred of. I broke it the rest of the way off and saw that that is where my pipe moves where the pipe bolts to the cat. So I have determined that I have a bad exuadt leank and rattle but only under a spefic amount of engine load becuase it twsits the pipe just right and allows the leak to happen. Anyway, No that i know what it is, I am in no hurry to fix it. Becuase I know its not hurting anything. But when i get a few bucks, I will have a high flow cat put on and have the pipe fixed becuase I already have a 3 inch flowmaster cat back... Thanks for all of your imput. It feels great to have identified it becuase I know it is nothing seriouse. Thanks again.
Ike