Brake "moan" from engine compartment

[d.n]

Hi all, I have this brake symptom that I've never heard before. When I step on the brake pedal (engine off), I hear a moan (like water pipes in a house) from the engine compartment. Any ideas what this could be? Check valve? Water/brake fluid in the booster line somewhere?

Things I've done along the way (it did this from day 1 and I haven't addressed it yet)

- new MC
- currently brake lines are not even connected to MC (noticed sound while bench bleeding the MC in car) and symptom persists. The vacuum line going to the booster is connected.

Thanks in advance

 

[pgilliam1]

Have a friend step on the brake while you are looking into the engine compartment. If you can hear it from inside the car, it should be easy to locate looking/listening directly at it. May be a rear caliper has air in it?
Good Luck and Happy Motoring!

 

[d.n]

Yeah I'll give that a shot. Currently no brake lines are attached to the MC. Just the booster vacuum line. I'll probably go home tonight and use a mityvac to try and suck the line dry. My guess is some fluid is in there

 

[BATMANs]

Look at the amount of people that looked at this thread from the word, "moan".

 

[d.n]

Look at the amount of people that looked at this thread from the word, "moan".

I bet there was only 1. The other 30+ were thinking they could help me out with some advice :biggrin:

 

[R13]

That's almost definitely the check valve. It'll be located along the vacuum hose that clips to the side of the coolant bottle in the engine bay. I suspect if you go listening for it with some help you'll be able to narrow it pretty quickly to that.

 

[d.n]

Yep you're right, it's the check valve. It was easy enough to trace and there's no liquid in the line. It's still holding vacuum in the other direction so I think it's okay. If it makes the noise with the car on, I'll replace.

Thanks for the help

 

[gsrboy]

Look at the amount of people that looked at this thread from the word, "moan".

I was LIED to! :biggrin: