Meraut

All right guys so heres the story. My girl friends 98 civic ex auto brakes' are acting up and i think its the brake booster but i'd like to be sure as always before you start replacing things. Here are the symptoms:
-Really hard to press brake pedal with very little braking power.
-Whenever the brake pedal is depressed a very audible hissing noise(like pressurized air escaping) comes from somewhere directly on the otherside of the firewall(behind the steering wheel)
-Lastly, whenever the brakes are pressed the RPM's shoot up to about 2k rpm(vacuum issue?).

So there it is gents, any quick responses would be helpful because shes driving my car too work since i got a few days off but i need to get it fixed up soon so she i can have it up and running by the time i need to go back. Thanks as always guys.

Toofpik

did u check the fluid level and for any leaks? It sounds like a booster problem but u want to rule out everything else while ur at it

NVturbo

????

Meraut

Yes I checked the fluid and the usual suspects

kyden

your signs do point to a booster issue. I would first make sure the check valve in the vacuum line works.

Meraut

How might i go about doing that?

jlaustill

Stop by your local parts store and grab 2 feet of 3/8" vacuum line, should be about 4 bucks. Then replace both lines and add good quality hose clamps(another 2 bucks). Blow both ways through each end of the check valve, it should be impossible against the arrow on it, and possible but hard the direction of the arrow to blow through it. If it allows you to blow both ways it is bad.

If you STILL have the problem after that, you have a bad booster. 90% of the time is is just a leaky hose though.

Meraut

All right ill give that a shot, i'll report back with the results when im done.

black97civic

If you heard a a vacuum leak when you press the brakes its the brake booster 100% positive. It's pretty common. If it where the line it would leak all the time.

black97civic

The check valve holds vacuum in the booster after the engine shuts off so you have brake assist if the engine dies. To check you can shut the engine off and either pull the line out of the booster and listen for air being sucked in or shut it off and pump the pedal. If you have a couple easy pumps then its holding vacuum in the booster. But since your booster is leaking it would be hard to check. You could pull the hose off and blow through each end. Air will go one way but not the other.

nealnanoHX

Yep sounds like the booster went out everything the OP is saying screams leaking booster. Low brake fluid for one should turn on the brake light on the dash. Replace that booster.

jlaustill

I would concur that it "sounds" like a bad booster, but you should NEVER replace a booster without also replacing the hoses, and nothing sucks more than replacing a 100 dollar booster to find out it was a 2 dollar hose

As for hearing the leak all the time if it was a hose, in my experience that isn't the case. Yes, it would leak the whole time, but people only seem to pay attention when they actually notice something is wrong, so many times it goes unnoticed until the brakes act up. That being said, it would surprise me if it were just a hose from what the OP describes

Meraut

Okay guys so i finally got under there, and i'm 100% sure its the booster. I tested the lines as suggested(thank you) No foul play there, i managed to get my hands on a factory manual with booster testing instructions and it failed those so i ended up replacing the booster and its good as new, also got a new vacuum line for good measure. Thanks for the help everyone.