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1G Brake pedal clunk and booster hiss with engine off

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Focused1

Probationary Member
17
0
Dec 22, 2009
Holly Springs, North_Carolina
This is a long one but I have included precise details in the hope that it will help someone help me.

I have a 1G eclipse GSX that I have owned since I was 15. Yes, I bought it before I could drive. It eventually became my weekend car but it is once again my daily driver. For that reason I have been fixing problems that I had just ignored in the past. Since it has been so long since the car was stock and in good shape I cannot recall the way it used to feel or sound. Basically, it may have always made a noise or shake and I didn't notice it until I drove it every day. Sometimes this has hindered my diagnosis.

The one issue I can't figure out is with my brakes. I installed a Baer big brake kit, probably around the year 2000, which consist of Baer calipers and rotor up front and Baer rotors in the rear with stainless hoses all around. These have been great for a very long time but the brake pedal has always felt different than stock after I installed these. I was told this is normal and that seems reasonable to me. No other mods on brake system except I recently replaces both rear calipers and pads with reman units about 3 months ago.

My car does not have ABS.

Two separate symptoms here:
1. Hiss from booster that starts about 5-10 second after I turn the car off and last about 5 seconds. It is fairly loud. Not as loud as draining the water out of an air compressor but similar sounding. This has been occurring for quite a while but I don't know when I first noticed it. I have never owned a car that did this and I cannot find if it is normal for my Eclipse.
2. When I push the brakes with moderate pressure there is a clunk feeling/slight pushback felt in the pedal, moving or sitting still. This is relatively new, within the past month or so. If I barely apply brakes this doesn't happen. More pressure and the pedal will feel normal for maybe half an inch then I fell the clunk, then a slight pushback(pedal seems to stay at the same level however) then the pedal continues downward normally. About a week after this started happening I noticed my rotors feel warped when I apply the brakes. Might not be related but maybe.

I have read all the forums and done the tests and the booster seems fine but I may have an intermittent problem or it only fails under certain circumstance. When testing/visually inspecting the booster I removed the master cylinder(MC). When I re-installed it there was a fluid leak where the MC mounts to the booster. I removed the MC and it seems I didn't center the pushrod and it was pushing on the side of the piston and not the middle. This caused the piston to wobble in the cylinder and let fluid past. I didn't see this but that's what I surmised. There did not appear to be any damage to the MC. I re-installed and it worked well for a few weeks.

Even with these issues my brakes work fine. The car stops.

Things I have done:
1. Verified factory vacuum hose with factory valve is installed correctly
2. Verified no visible fluid leak in/from booster
3. Verified Booster function: it holds vacuum, pedal drops when I start engine, pedal isn't any more firm than I can remember, I read some other test in the forums, I can't recall them all but it passed all of them
4. Verified no vacuum leaks anywhere
5. Correctly bled entire system with new fluid

Things I thing may be related:
1. I need all 4 axles replaced. I want to replace all 4 at once. I have a 3 bolt rear and I can't find parts for the rear. I have reached out to another member here and he will be sending me his 4 bolt rear lsd with axles in the next week or so.
2. I need 4 tires and an alignment. I only want to do this once so I will wait until I have the axles installed.

I've read about partially torn diaphragms and such but I don't want to throw parts at it. This is my daily driver again because I sold my other vehicles because I need the money. I have a new homebrew store in Apex, NC which takes up most of my time and all of my money. Does anyone have any ideas or any definitive tests?

Thanks in advance for any help!
 
It holds vacuum when I attach a vacuum gauge to it. When I shut the car off it sounds like it holds vacuum for 5-10 but then releases it.
 
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Here's the video. Let me know if this uploaded correctly.
 
Thanks for the suggestions. I have nothing to compare it to so mine could always done this. Before I start changing parts, does anyone's booster act like this?
 
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