So I have a 2002 Blazer 4x4 4-door with ~150k miles on it. It is running perfect except this strange noise that happens when engine is cold for about 10-15 minutes.

https://www.dropbox.com/s/pkqbucs19v...617_195156.mp4

No CEL or any fluid leaking.
It's not coming from the fans/belts/front of the car.

I don't feel any clunking/slipping or any issues shifting, and the transmission fluid is a healthy red, although I did see some tiny air bubbles in it.

Any help would be greatly appreciated!

 

i had a starter that wouldnt disengage sometimes (the gear wouldnt retract) and it made a similar noise.

 

Sounds like a heat shield is vibrating...but quits when it get hot and the metal expands.

 

Hello,

Did you ever find the cause of the sound?
I have the same sound however I removed my heat shield some time ago since it was loose and rattling.

Thanks.

 

No, unfortunately I've been extremely busy =(. So, did removing the heat shield stop that noise? And where was the heat shield located? I could not find anything loose last time I checked but didn't have time to check closer to the engine.

Thanks for helping. I'll update as soon as I figure it out.

 

This may sound dumb, but what oil filter does it have in it?

I had a 98 that was very noisy when first starting it and until warm. I learned that having the right oil filter makes a big difference in these. I had a FRAM when it was loud. Changed to a ACdelco filter and made a world of difference. No more weird noise on cold start up.

Not sure exactly why this makes a difference, but has to do with the horizontal position of the filter and how quickly oil gets to the upper side of the motor. What I was told at least.

 

The heat shield (thin sheet metal) I removed was tack welded around the catalytic converter. Not touching the catalytic converter itself but just around the top and bottom of it most of the welds rusted and I just pulled it off with a little force.

That ended one rattling sound. I now hear another rattle when moving from parked very slowly. I'm wondering if the parking brake cable may just be vibrating against the chasis. Jeep Laredos are known for it.

 

it could be that or you are dragging the brakes a little bit when you back and that is what you are hearing.

as far as Quick was saying about the oil filter, are you sure that you had the right oil filter? Fram does make filters with check valves and such and some of the are actually reverse flow. i have just never heard of such a thing thats all.