2003, V6, 5spd, 193,000 miles.
1) I first noticed that when at a stop light (drive-thru, etc) I would hear a squealing sound (sounds like: eeeeeeeeeeeee) coming from under the hood. I could pump the brakes and it would change pitch and volume. My brakes don't really feel mushy, and the pedal doesn't really go to the floor, but sometimes it feels like it is creeping ever-so-slightly...a small enough amount to make me question whether or not I'm imagining it doing so.
I've also noticed that my brake performance is as good as ever. However, I've also noticed that if I run down the interstate for a few miles and don't hit the brakes, that the first time I press on the brakes, there seems to be a significant amount of resistance...then the feedback seems to normalize.
2) I then noticed (not that it necessarily came later, but it started happening at about the same time) that when sitting at a stop, engine idling, that my RPMs were about 550. Typically, with no extra load (PS pump strain or A/C) the truck used to idle at 680 RPMs and with the A/C load, it would kick up to about 780 RPMs. Now, it idles at about 550.
Lastly, both #1 and #2 are inconsistent. It happens when I first start the truck sometimes and sometimes it doesn't. It happens when its hot in midday and even in the cool of the evening. I can't deduce a pattern on when it tends to do either one.
So what I tried the other night just messing around was to squirt some water around some of the vacuum lines and connections around the intake and brake booster. I did hear some sucking and replaced that hose. It did seem to be less frequent, however it is still happening.
I still believe it is vacuum related. A friend told me to use some carb cleaner (it tends to change the idle when it makes its way into the intake). Anyone seen this before. Am I on the right track checking for vacuum leaks.
Thanks in Advance.