"Wooshing" noise like running water behind the dash on cold start?

[ero2]

Hey all!  I've never encountered this before in a vehicle, is it potentially the fuel pump, or something related to the AC potentially?  Did a search and couldn't see anyone else with issues like it.

 

Thanks!

[Pharmer]

I definitely have this.  It sounds like coolant flowing through the heater core, but no leaks.

 

-Steve

[calgator73]

There was a problem on another GM vehicles as well and it usually requires getting air out of the system.

[nlindste]

I have the same issue with mine ever since the lifters were replaced.  I betting that air got into the coolant system and just needs to be bled off.

 

Nick

[Gangly]

I had the same problem since day one on my truck, and I was also steadily loosing coolant over an extended period of time.  I took it in and they bled/pressurized/flushed (or something) the system and both of the issues were resolved. 

[BB68]

You have an air lock. This is why I always use a vacuumed fill on newer anything as they have so many spots to hold air in

 

[Zroeffectzx]

New to the Forum and also first time Silverado Owner. Bought a 2021 Custom with the 5.3L. I have notices this recently after owning the truck for about 45 days now. No issues or leaks besides the noise.