brakes went out (90% of braking power gone at least)! help please - 89 240sx

[onosqv]

Hey guys, I have no idea why, but when I came home from work today, the brakes mostly went out. Basically, what happens is that I have to REAAALLLYYY stomp on the brake pedal to get it to stop.

Fluid level: fine - no visible fluid leaks anywhere Current brakes: z32 front & rear brake conversion w/ master cylinder & conversion lines

Pads: life is fine on all 4

Thing I noticed: While the car is running, as I press the brake pedal I can here a "ssshhhh" coming from what seems to be right near that area inside like air leaking - brake booster line leaking - I have no idea, I've never had this problem before tonight.

When I start the car, while it's still "cold" & in Park, if I press and hold the brake pedal, I hear the air leaking & the rpms start dropping - kind of like rough idling. I'll be checking for vacuum leaks tomorrow I suppose, but I have no idea where to look or how to really check.

Thanks for any help.

[D Money]

maybe the brake booster, or tube broke? If you stomp on the pedal does it stop as quick as usual, how long have you had z32 brakes?

[onosqv]

Thanks for the quick reply. I haven't had a chance to check it because it's 1am and me w/o a partner to press the brakes while I check around things.

Anyway, I've had the front brakes for a couple months or so, the rear installed for about a month.

If I stomped and hold basically like "emergency o my god" braking, it brakes about the speed of "normal la di da" braking. What I had to do a couple times is use the ebrake to assist me in braking - good thing I decided to go through the trouble of getting a sort drum ebrake part on the z32 conversion.

So everything I should be checking is in the engine bay right? Nothing under the dash/by the brake pedal? I'm asking this because I "hear" the noise from inside, but could just be coming from the engine bay - waiting for that partner tomorrow once I have time.

THANKS

[Shift__BODOM]

it may very well be a crack in your vaccum hose running off the top of the brake booster. you can also take a look at the check valve that's between the brake booster and intake manifold. it connects the afforementioned vaccum hose from the brake booster to the vaccum hose that goes into the intake mani. i'm supplying a pic from the factory service manual that lays out how to check for airtightness and correct operation. i suggest you try this first before you look into anything else.

[NISTECH]

The booster diagphram is blown out. The test above will prove that. If you check it and you dont have the pedal drop and rise mentioned in the 2 tests above exactly as stated your booster is toast.

[onosqv]

Thanks to all 3 of you.

Yes, it looks to definately be the brake booster. All the lines in the engine bay from brake booster to check valve seemed ok, no cracks, no hissing, etc.

Inside the car, (thanks to that great diagram). When I press the brake pedal I can hear & feel the air coming out when I put my fingers near where the bolt connects to what look like the diaphram?

So, the only way to fix this is to get a completely new brake booster I guess? Checked dantech's online catalog and doesn't look like they sell just a diaphram.

So, based on this, my brakes didn't "fail" persay, so I can still "safely" drive my car around, I just have to stop like "oops, cliff ahead." yea?

Freakin junk yard wants $100, BAH. And ebay auctions that only want $10-15 don't end for another week... freakin a.

[NISTECH]

Pick & pull ! like 20 bucks