Odd brake-problem sound

The brakes are not working right on my '94 Cav. much of the time lately, at slow speeds. If have to push way to the floor at stop signs. When this happens, there's a strange noise, kind of like a squawking sound. The noise is not at the wheels (pads, shoes are good) but maybe in the vicinity of the master cylinder. Anyone know what this might be?

The brakes are not working right on my '94 Cav. much of the time lately, at slow speeds. If have to push way to the floor at stop signs. When this happens, there's a strange noise, kind of like a squawking sound. The noise is not at the wheels (pads, shoes are good) but maybe in the vicinity of the master cylinder. Anyone know what this might be?

check vacuum hoses that go into the power booster the size of a pie plate, behind or next to master cylinder

Thanks. I see a single vacuum hose on the booster. It looks good. Anything else I need to look for? There's no fluid leak anywhere.

The brakes are not working right on my '94 Cav. much of the time lately, at slow speeds. If have to push way to the floor at stop signs. When this happens, there's a strange noise, kind of like a squawking sound. The noise is not at the wheels (pads, shoes are good) but maybe in the vicinity of the master cylinder. Anyone know what this might be?
hi gln7 check the fluid make sure it`s clean and no gunk has settled on the bottom,if there is gunk clean master cylinder ,add fluid and bleed system.also undo that hose off the booster,clean it if needed and start vehicle and pump to get your pressure. if this is not it ,and there is absolutely no leaks in the system I think It`s your master cylinder that needs replacing

Thanks. The fluid and booster hose seemed clean enough. If it's the master cylinder would it be making this strange sound, sort of like a low-pitched bird squawking for a second or two? I'm also noticing a hissing sound when brake is depressed.

hissing .........vacuum leak

If it's a vacuum leak, it has to be either the booster or vacuum hose? Thanks.