98 blazer 4.3 auto trans 140,000 miles

So upon cold start i get a strange noise in the cab. It sounds almost as if the abs is kicking in, kind of like a crinkling or rattle noise. It happens at lower rpm and only when I put it in gear. In the cab is sounds like it coming from the brake booster area. It happens with or without the breaks applied. I thought maybe power steering, however it occurs regardless of turning the wheel or not.
Any opinions or thoughts are greatly appreciated.

Cheers,
Bassson

 

I would check your exhaust system first.
When it's cold and with the engine off, check if anything is loose. Grab the pipes and move them around. Are the hanging brackets OK? Is the outer CAT cover loose or can it rattle? Bang on it with your hand.


Next start the Blazer. Run your hand around the pipes and see if you feel a leak anywhere. Watch you don't burn your hand !!!


Next... cut a 3 foot piece of heater hose.
Now you will use this by holding one end of the hose to your ear and the other end sticking out from your hand.
That helps you locate the location of sounds.
After the engine is cold, open the hood, start the engine.
Feed around the hose listening for that noise.
Run it along the exhaust manifold and exhaust pipe connection.
Run it over the valve cover, etc...
Be careful around all the moving parts!
The cool thing about the hose is you can get it close to many things while keeping your hands away. (hot exhaust, pulleys, etc) It really helps to pin-point the source of the noise.

 

It sounds more like it was a vacuum leak rather than a exhaust system leak. its a very hard sound to explain. thanks for your advice though.

 

i think im having the same problem, is it only at cold starts too? i hear something i assume is near the break booster but it doesnt happen everytime its cold

 

yea i only really started noticing it on cold mornings upon first start, its a strange sound almost like slurping or crinkling paper. Ive tried hearing for it in the engine bay by opening the throttle body slightly, however it only really happens when the blazers in gear. Therefore, i do not think its exhaust related. I assume vacuum related. All vacuum lines seem snug.

 

well to rule out some vacuum lines, do you have 4wd? if so do all 4hi and 4low and if you have it equipped 4auto work? and does cruise control work? and also the climate settings (like floor defrost, vents etc)