AS it says in the title I have a 2003 Chevy S-10 4.3L, that I have a vacuum leak I think. when I step on the brake I can hear something under the dashboard hissing. When I take my foot off the brake it stops. Also my heater regulator is Not working, and when I come to a stop light and stepping on the brake in gear the engines idles very rough. If I place the transmission in neutral and stop it does not idle rough? My question is this. Where is the vacuum module that is under the dashboard that obviously is causing these issues. Im thinking that the diaphram i the module is ruptured and I need to replace it. Any one have any input and help for me. It really cold here in St. Louis driving around with no heat from my heater?

 

Well I have heard this noise with the brakes on a 99 jeep grand Cherokee. on his jeep it is the brake booster that is bad. Also what I was told when you do the booster you should do the master cylinder because you can mess the seal up in between however I have seen just one at a time done and worked fine..Also I know on my 01 s10 with 4.3 vortec there is a big vacuum hose that goes to the booster and if its unhooked it changes the Idle.. maybe that has to do with the whole vacuum leak and issues your having. I would look into that.

 

I was just reading a reply from tymr287 and he told someone to try spraying carb cleaner around the vacuum hoses to see if the motor runs any differently , that will help you find out if you have a leak and if you do where it is. If it works thank tymr287