'95 Blazer brake issues

[ranger_mclaren]

My wifes nepthew has a '95 blazer. He called me up asking if I could come over to look at his truck he thinks it has air in the brake lines and it making noises when the brake pedal is pushed and pedal is hard to push down. I told him usually if there is air in the lines the pedal goes to the floor. So I went over to take a look and I drove the truck in the parking lot, you literally half to stand on the brakes and the truck doesn't stop it rolls to a stop. I noticed there is a definite air sound coming from under the dash. I pulled the cover and pushed the pedal seveal times I noticed some slite air coming out of the boot on the back side of the master cylinder under the dash. I think the brake booster is bad but I don't want to tare in to it unless thats what it really is what do you guys think?

 

[martin]

Sounds like a bad booster to me.

 

[BRUTUS_T_HOG]

bad booster or bad master cylinder come to mind. how do the brake hoses look? any work done recently?

if the hissing under the dash is constant then it probably is the booster, also if it hisses constantly while the pedal is held down.

if thats not the case then you can pump the pedal until the booster is empty of vacuum, hold the pedal down and then start the engine. the pedal should drop.

i've had these shitty S body trucks do this with a bad master cylinder also, when you pump the pedal you should have 2 small squirts of fluid in each reservoir with the cap off, the fluid will just raise up like a column

 

[ranger_mclaren]

bad booster or bad master cylinder come to mind. how do the brake hoses look? any work done recently?

if the hissing under the dash is constant then it probably is the booster, also if it hisses constantly while the pedal is held down.

if thats not the case then you can pump the pedal until the booster is empty of vacuum, hold the pedal down and then start the engine. the pedal should drop.

i've had these shitty S body trucks do this with a bad master cylinder also, when you pump the pedal you should have 2 small squirts of fluid in each reservoir with the cap off, the fluid will just raise up like a column

Alright I'll half to check out the reservoir. The hiss is constant the whole time the pedal is depressed. No, no work was done thats the first thing I asked cause other wise no air should have gottin in the lines. I didn't take the wheels off so I didn't look and the lines but I will. Thanks.

 

[BRUTUS_T_HOG]

well a constant hiss while the pedal is held down means its a bad booster