I have a 2008 Dodge Charger that has a vacuum leak in the EGR system, the computer does not detect the leak, You can Hear the leak when your are driving as a low to high pitch squeel. It does this mainly in the fall and spring when the conditions are just right. Does not do it when the engine is cold. After the engine heats up you can hear it at an idle. The dealer has tried to fix this, but the problem keeps coming back. It has to be leaking and showing a code before they look at it - because it is now a complimentary fix for them...but after the car cools down for 20 min it "goes away"... I take it in, but by the time they look at it the problem is not evident. I have had it send the car into limp mode, but shut the engine off and the limp mode clears itself.
Has anyone else had trouble similar to this?
Might be a good candidate for using the propane method for locating a vacuum leak. When it is leaking take a propane torch and open the valve. Without lighting it, pass the nozzle near likely sources for the leak. The idle will change when passing near the leak and the engine pulls the propane into the intake system.
The leak is in the EGR connection on the engine - between the engine & firewall (in the center of the engine).