mx7roadster

today my brakes all of a sudden gave out. i was scared because i almost ran a red ligh. When i got home i opened my hood and had a friend pump the brake pedal while i was checking out the brake system. I heard what sounded like air coming out of somewhere and when i ran my had through the brake booster i felt air coming out. Does anybody know why that happens? I know i'm ma have to change my brake booster, Does that mean i'm have to change my brake master cylinder 2? i was also checking them out on ebay and i found one that was for a 1st gen that had rear disk brakes, would it fit mine even though i have drums? any help would be appreciated, thanks guys.

Manntis

as long as you weren't just feeling a slight amount of air moved through one of the openings in the firewall when your friend pressed the pedal...

Start with the simple stuff - check your brake fluid level.

If you find it is the booster itself, what year is your car? I've seen others have to move their clutch master cylinder to accommodate a different sized booster

mx7roadster

its an 83'

DivinDriver

iTrader: (15)

If just your booster failed, you don't "lose" your brakes - - they just get a lot harder to operate, requiring much more pedal effort.

If your pedal effort stayed the same or got a lot softer and your brakes did not stop the car, you lost brake system hydraulic pressure - - probably a master cylinder seal failure. Many times a leaky MC will leak fluid into the booster, rotting it out too. Brake fluid is a strong solvent, and attracts water which accelerates rust, too.

If your pedal effort suddenly got way hard but the brakes still work if you stand on them, then it was just the booster that let go.

ray green

iTrader: (14)

The brake booster is vacuum operated and when the vacuum isn't working (because of a vacuum leak, for example) you will lose most but not all of your braking power, as DD points out if the booster "fails". You just need to push the peddle down a lot harder, both a nuisance and a safety issue, in my opinion.

The "air sound" you are talking about might be a vacuum leak in the rubber hose connecting manifold vacuum to the booster and the air you felt coming out of the booster might have been air leaking from the same hole as the booster is operated.

So I'd look for an air leak in the vacuum feed to the booster before doing anything about changing out the booster.

mx7roadster

yea i actually drove the car today and i actually had to put the pedal all the way down to actually stop. I'm ma check all the hoses going to the booster to check if its any of the hoses that are leaking. thanks guys.

DarrenTRS

iTrader: (1)

So the pedal is soft? or is it super hard? Soft/Long Pedal means you have a hydraulics issue not a Booster issue.

mx7roadster

Well when i press the pedal it goes down to almost hitting the ground and thats when the car stops. When i first noticed the problem i would stop my pumping the break pedal to get pressure, in other words i would have to bring the pedal back up to get a little bit of pressure back down.

ray green

iTrader: (14)

emmm, sounds like the master cylinder quit.

DarrenTRS

iTrader: (1)

Yea thats not the brake booster, that is something wrong with the hydraulics system i.e. torn line, worn out master, bad brake caliper. Check under the car for any leaks as well as check the hoses and if you cannot find a single leak then you might have the cylinder leaking back into the booster which can destroy the booster if left for a long period of time.

DivinDriver

iTrader: (15)

Odds are it's the MC; you could also have air in the lines from a bad seal, hose, or even a loose bleed screw.

Step one would be to thoroughly bleed the system and inspect closely for leaks. With rear drums, inspecting includes pulling the rear wheels and drums, since a leak inside the drum can go unnoticeable for a long time. Readjusting the rear drums (manual adjustment is required) would be good, too.

If a good bleed and inspection doesn't reveal any leaks, odds are the MC is bypassing internally, not letting you get pressure up.

mx7roadster

yea i forgot to mention that i looked under the car and i found fluid on the driver side of the car by where the front left wheel is at. I'm not sure if it came from one of the lines or it just dripped down from the brake system. I inspected the rear drums and the are both fine with no leaks.

Manntis

Check the flexible line that goes from the hard brake line to the brake cylinder. You can get stainless ones to replace the stock rubber.

DivinDriver

iTrader: (15)

Air in the lines from a leak (or from running too low on fluid in the reservoir, through leaked losses) can cause the exact symptoms you reported. Finding the source of that leak is now your #1 priority.

Even a small amount of air in the brake system can ruin braking performance, because the air will compress when you step on the pedal rather than transmitting the hydraulic pressure to the calipers.

trochoid

iTrader: (6)

Get a helper to pump the brakes. Clean off any brake fluid with brake cleaner, the start looking for a fresh leak. When I finished the big brake upgrade on the widebody, I couldn't get the brake pedal to firm up. Finally found a drip on the rear axle while bleeding the right rear caliper. The hardline coming from the tee to the flex hose on that side had rubbed/rusted to create a very tiny leak. Once that was repaired, still had trouble getting a firm pedal. While I was bleeding the last caliper, I felt a drop on my head. Somehow I had cross threaded and stripped one of the fittings on PPV.

Pedal has firmed up but still not happy with it. My 'helper' had the e-brake on during bleeding.

Siraniko

iTrader: (13)

my son did the same thing to me , took me quite sometime to figure it out