High pitched brake squeal and possible vacuum leak

[Hawkeye18]

Hello,

Long time forum viewer, but don't post often. I have a 01 sport 4x4 v6 sohc with 214K miles. Had the front brake pads done about a 10 months ago (nothing fancy, possibly cheapo brand replacements), everything was fine with brakes at the time until about 2 months ago. The brakes began to have a very high pitched whistle just before coming to a stop (still do). I also noticed when pressing the brakes at a stop light I lose pressure at the pedal and it goes all the way down (brakes still apply enough force to keep car stationary). On 2 occasions when also coming to a stop (about a month ago 1st time and a week ago 2nd time), the vehicle "slid" forward about a foot and then it was back to normal. It was raining both times this happened, but not enough for the tires to slip. Brake fluid appears clean, but still plan on bleeding the brakes this weekend. Any ideas on what I should check/test?

Also, I'm almost positive there's a vacuum leak as my vents only blow air through the defrost and a little through floor vents (happened sometime after brake pads were replaced). I'm not concerned about the vents and will get around to them this summer as I'm busy with school. But I was thinking, could the vent issue/vacuum leak be related to the brake problem?

I do have larger than stock tires 265/75/R16 and haven't corrected the speedo for them yet, could this mess with the ABS system?

The gear selection indicator in the dash doesn't work, but I can still figure out what gear I'm in and plan on fixing that in the summer along with the vents. Does the indicator have an effect on the transmission and other components or is it purely for visual confirmation of which gear is selected?

 

[koda2000]

As long as all 4 tires are the same diameter, nothing should be happening with your ABS, but as you are aware your speedo will be off.

You definitely have a vacuum leak somewhere if your HVAC is only blowing out the defroster vents. Could be anywhere. Start hunting. A smoke test is probably the fastest way to find a vacuum leak.

You master cylinder has an internal leak. That's why your pedal drops/sinks after stopping. It will need to be replaced.

Brake squeal is usually caused by the pads vibrating on the rotors. I've also seen small stones stuck in the brake pad, but that's very unusual. There's a sticky compound that you can put on the backs of the brake pads to stop them from squealing. More expensive brake pads have a "anti-squeal" material on the backs of the pads and don't require anything else.

 

[J_C]

It seems like the brake job was incomplete, maybe whoever did it just slapped new pads on and that was all? I'd take the wheel off and look at everything, pad thickness, rotor wear, caliper piston corrosion, caliper slider lubrication, caliper slide rail corrosion, and yeah, see if there's air in the lines by bleeding them. I don't know what you've checked yet, do assume the master cylinder reservoir is topped off.

Gear selector indicator is only a visual confirmation.