noise from dash

hey everybody...I have a 2000 blazer it has been making a weird noise for some time now. Some describe it as a rattle type noise. I cannot figure this out. It seems to be coming either from the back of the motor or in the dash.(behind the firewall?) It happens at idle or coasting after acceleration. It goes away once you step on the gas and will come back after you release it. One of my buddies suggested that it may be a restricted flow somewhere in the cooling system( heater core maybe). If so could a coolant flush solve it? I would appreciate any feedback. Thank you.

Try to pinpoint the noise.
And what it sounds like.
Good luck

I drive a 2001 Olds Bravada and I get the same thing. I think it's the power steering fluid. It stops when I add some but it starts doing it again awhile later. It doesn't seem to be leaking really bad but that seems to fix it. The power steering system may need flushed or it may have air blocked in the system. I'm not 100% sure that that is the problem but it is a good possiblity. Let me know if it worked. I'm curious to see what fixes it.

hey thanks for the tip...i checked the fluid, and its fine... i guess it could still need flushed... i think this one may need a shop...i have no clue. One other thing once you stick your head under the hood its not as loud. its louder from inside the truck. and to describe the noise a little better. it almost sounds like the noise your computer makes when its thinking or loading something big.

Can you feel it anywhere? Seat? Steering wheel? Or just HEAR it???

Could be a vacuum leak witha loose vacuum line, or could be a low coolant in the heater core- which is very common- which causes a bubling/water running sloshing sound.

I know the noise that I'm hearing isn't the heater core. Mine went bad last winter:banghead: I bypassed it so it has no fluid in it and no pressure. Could it be the bearings in the blower motor? Or mabye the blend door vibrating? Just some ideas. I'm just curious if anybody has ideas. Ya'll got me wondering about now.:screwy: All good.:smokin:

the heater core sounds like a good idea...but the noise seems like it may be comming from higher up in the dash...im not sure..i am do for a coolant flush will that go thru the heater core too? and no i cannot feel it anywher, its just a noise. and its getting irritatiing...have a girl in the car and i always get "whats that noise"? it does sound like fluid flowing issue. I verry well maybe wrong but i dont think it would be a vaccum line. Thanks again for everybodies input

Yes a coolant flush will incude your heater core. It is directly included in the engine coolant system. Have you noticed if it does it when it's cold or hot out? Any difference? I haven't really payed much attention to it in the last year or so. It's been doing it for a long time. Hasn't gotten worse. Though I have noticed that it has been happening less. And only when the weather is cooler or the engine is cold. The thing that throws me is that my heater core is disconected. We may have different problems but it sounds to be the same. Just keep poking around and see what you come up with and I will do the same.

well i had the coolant flush today and no luck...still have the noise. while doing so they found that my lower intake gasket is leaking...i already did this a few years back and dont feel like doing it again so im gonna take it in and i live in cleveland and its getting cold out!! I talked to the guy on the phone and he seemed to know the noise right off the bat and said it might be air stuck in the heater core. idk i thought the coolant exchange would cure that issue. But then again thats why im on here asking questions bc im not a mechanic. so we will see. so no heater core? i take it u live in warm weather?

Even if you have a coolant flush, if there was air in the system, it could still very well be in there. The heater core in these trucks is actually higher than the rest of the cooling system. If air starts getting into the cooling system as a result of a bad rad cap(or lower intake gasket leak), it will migrate to the highest part of the system, and in this case its the heater core. Once the air gets in there, it will make a sloshing gurgling sound.

If you infact have leaking intake gaskets, get them changed as soon as possible. If you plan on keeping the truck for a whicle and don't want to deal with intake gaskets again, Fel pro makes the perma dry plus gaskets that have an aluminum core carrier instead of the plastic whcih will completly solve the intake gasket problem.

Also the trick to getting all the air out of the heater core is to raise the front of the truck up higher. Car ramps are perfect for this. This puts the rad the highest part of the cooling system. With the rad cap off, and engine running, it will purge the air out of the system.

so no heater core? i take it u live in warm weather?

I answer, no, I don't like in a warm climate. I'm from northern Indiana but I'm stationed in Virginia. The Humidity is higher but it's about 40 here in the mornings. it's bearable, but still sucks. Winter time brings 10 degree weather, Ice storms and crap like that. No defrost sucks. Kinda off subjuct. Now I'm really confused. If my HC is bypassed, what would the noise in my dash be? I've started noticing it more often and it's driving me NUTS!!:banghead: Thanks and good luck.

hey, well maybe you still have air in your system and since its not in the hc it may be in the next highest point? I saw your post on the HC my buddy did one on a 98 s-10, siad it took him prolly about 8 hrs. but it was also below zero out. Blazes...thanks for the tip if the shop cant get the air out i will give that a try. Mudslinger...you should give that a try, Lifting your truck up pop the cap and let it run. nothing to loose besides 15 mins?

sounds good. couldnt hurt i guess. i'll let ya'll know if it works.

It is 100% your pcv valve they only cost 2 dollars and take ten seconds to replace when they go bad they rattle very common to the 4.3 be carefull mechanics will screw you on this!!!!!!!!!

It is 100% your pcv valve they only cost 2 dollars and take ten seconds to replace when they go bad they rattle very common to the 4.3 be carefull mechanics will screw you on this!!!!!!!!!

Dapdag- close but no cigar- Funny -I think i just fixed my problem 30 minutes ago. Its been two years with this damn noise and i hope i finally pinpointed it! Blazes 9395 was correct ( i think) it was a vaccum hose that ran to whatever the PCV valve hose connects to. (under the intake and next to the throttle body.) There is a seconde small vaccum hose that comes out of it. I could never see it because a wiring harness ran right over it. There was a kink in the vaccum line right next to the connection to the this part that i do not know the name of. Thanks to everybody fro the help.