High Pitched Noise from Front

[tmt502]

Hey all, I've been trying to look for threads/posts related to this, but can't seem to find a match.

When I first get in the truck for the day and depress the brake pedal to shift into gear, I normally hear a high pitched squeal, before I even shift. The noise sounds like it's right in front of the dash, where the master cylinder would be. It normally continues while I'm moving the shifter and seems to dissipate after a few seconds. Maybe lasts two to five seconds. After that first time, it doesn't make an appearance until the truck has been sitting for a while, I'm guessing long enough for everything to cool off.

Is this the master cylinder going bad? Or a leak somewhere?

 

[OR VietVet]

The squeal is likely the first signs of a brake booster starting to leak vacuum. If the squeal/squeak is constant and then eventually dies out, that is my best guess. If the squeak is just when depressing the brake pedal, then I believe the pivot point of the pedal needs some lube.

 

[tmt502]

The squeal is likely the first signs of a brake booster starting to leak vacuum. If the squeal/squeak is constant and then eventually dies out, that is my best guess. If the squeak is just when depressing the brake pedal, then I believe the pivot point of the pedal needs some lube.

It is a constant squeal that fades out. Definitely not a squeak from the brake pedal.

 

[OR VietVet]

Then now is the time to get a mechanic's stethoscope, some come with horn attachments to help with some noises, and find the location. Your guess at the noise location was pointing me to the booster or brake pedal.

 

[tmt502]

Thanks, I'll look into doing that.

Strangely enough, when I started up yesterday, I depressed the brake pedal to shift into gear and.....no noise. I don't get it. I'll see if it's back today. Would a vacuum leak be temperature dependent? The weather is a bit cooler now.

 

[OR VietVet]

What is causing a vacuum leak can be effected by the temps.