Noise from inside the cab

I have a 93 s10 just replaced the heater core. Now i have a noise coming from inside the cab. The noise sounds like someone blowing across the top of a bottle. the noise only happens when the engine is warm and at high rpm. Any suggestions?

please some one help.

Is everything put back together right? is the blower motor hitting anything?

Under the passenger side of the dash, if you remove that panel thats down there, there is part of the heater ducting that has a gap in it. make sure that its covered.

I think my heater core had been done already because someone else sealed it off with duct tape.

I just did it to my 92 and I have a similar problem. I took the first heater core back out and returned it only to get another and its doing the same thing. And the second time I was super careful not to make any mistakes. Its crazy it sounds like the core is resonating when I bring up the rpms. I jumped out the core and all is quite so I know that the core or how its mounted is making the noise but how??? At this rate I will live with it for the winter and investigate again in the spring. Anyone have any ideas on this? All I can say is I made sure I put it back with all screws tight and everything lined up.
Ps I replaced it before around 90k miles with no problems, now a few miles later ( 193K miles to be exact) it was time for a new one.


I have a 93 s10 just replaced the heater core. Now i have a noise coming from inside the cab. The noise sounds like someone blowing across the top of a bottle. the noise only happens when the engine is warm and at high rpm. Any suggestions?