So I've always noticed after starting the car and letting it run for a bit, there would be a high pitched beep/whistle sound - sounds like it was coming from the engine bay, and was electronic.

I just replaced the rear rotors, brakes, calipers, and put steel braided brake lines, and now if the car is in Park (or stopped) and I let my foot off the break pedal, I get a longer beep/whistle sound. The car has no lights on the dash, and I have no clue why this is happening. Even checked the brake fluid, and that's topped off.

Would anyone have an idea why this is happening? Could it be possible that I haven't replaced the front yet, and the braided rear lines and stock fronts are causing something to be off?

 

Sounds sort of like a vacuum leak, probably the BRAKE booster circuit.

 

It could be the vacuum assist pump check this thread out for its location

https://www.chevyhhr.net/forums/hhr-...ntalled-44863/

 

Thanks guys. It seems whatever work I did today is causing this issue, so I hope this can be easily adjusted. The pedal also feels a little softer than it did before, so maybe some adjustments can fix all this.

 

After you did the rear pads did you adjust the parking brake ratchet?

 

Yes, my brother did as I was in the car. I was stepping on the pedal to bleed the brakes, then after I finished that I was lifting and lowering the parking brake handle for him to adjust. At first, I had no parking brake but after he adjusted it he said it was catching.

 

So I think I found the AC Delco replacement part - ACDelco 20804130 GM Original Equipment Power Brake Booster Auxiliary Pump Assembly.

Amazon with Prime could get it to me by Tuesday (Monday if I pay the expedited shipping). Looks like I'll be crawling under my car to see if this is the issue! Hope it's an easy fix

 

If I remember correctly, the vacuum pump was only installed on automatic trans cars. It was only designed to run for the first portion of the engine's warm-up due to the low vacuum produced during warm-up. If you are getting a whistling only during that time, as you've surmised, it most likely has to do with the pump. If you have a vacuum leak, it should cause a stiff pedal as you would not be getting full vacuum assist from your booster.

My guess is you've gotten some moisture in the pump at some point and it's caused a failure of the pump.

The A.I.R. pumps on a lot of the '00's GM applications were notorious for this.

If it's bad, and you're going to end up replacing it anyway. You may as well try giving it a shot of oil into the intake side before buying a new one..

 

It is a 2010 Auto SS. After checking the link OldBlue sent, I did find the Vacuum Pump Assembly, and when starting the car you can definitely hear something from that area. Makes the noise at startup and when stepping off the brake pedal after pushing it all the way down (in park, or idle).

When you say pump, you mean the vacuum pump, not the fuel pump right? Fuel pump is in the rear (So I think I just answered my own question).

Since it's getting cooler here in PA, there usually is some moisture buildup on the car in the morning, that could be how moisture got into the pump? Or the tube going to the Vacuum pump has a hole in it somewhere...

 

Could be the tube is cracked and sucking air and moisture into the vacuum assist pump.
The hose should be easy to replace , try it first and possibly save the cost of the pump!