Brake booster

[dandanger]

I have been having veeeery bad/spongy brakes for at least a year now. Pads have been changed, fluids changed two times and all calipers work fine and no sticking. No fluid is leaking. Check valve tested and works. I ended up that there can be no other fault than the booster(vacuum is dropping when pressing the pedal, and my a/f ratio also goes lean if I press brakes hard when idling), so I ordered a oem booster kit that includes everything inside the booster. Problem is now that the order was in for two months, and they informed that kit is no longer available, also other sources tell the same, not available.

Question is has anyone put some other models brake booster in these, or could a diaphragm/kit from some other variant of galant fit? Only bolt-on solutions or near bolt-on.. Regarding the service manual, the brake booster "boost level" is different from the "gti" version(n/a 4g63), and part numbers also differ.

Also interested that how common is this problem in these cars? We have only a few vr4's here in Finland, but lots of Dynamic-4 Galants, which are almost identical to vr4 but with the 150hp Gti engine, and I haven't heard of booster problems.

 

[EHmotorsports]

I would remove the two nuts holding the master to the booster to make sure the master isn't leaking and causing the booster to go bad. Most cases a booster will fail and make a hard peddle.

 

[dandanger]

Could check that too. Pedal is very hard engine off, but when idling or driving I can press the pedal to the floor if braking very hard. Car stops and I can drive in normal traffic, but it takes a lot of pressure to make a quick stop.

I have never taken the master off, should I prepare for brake fluid leaking on the ground even if there's no leak, or should it be dry if the master is ok?

 

[prove_it]

You have a leak, bad rubber lines, or a failed master cylinder. Sounds like the master is fine to me. If the diaphram was shot from leaking brake fluid you would always have a hard pedal. It's creating brake boost, but something is wrong with the hydraulic system.

 

[dandanger]

Okay. I'll speculate some before I get to the car later this weekend..

I'm quite noob what comes to brakes,or more on the hydraulic part. I'm just wondering that if there's no fluid leaking anywhere, where does the vacuum dissapear when I press the pedal? I had a vacuum tester/pump connected to the hose/check line just as the instructions say when testing the booster and vacuum line. When pumping vacuum and just keeping it there, there is no leak. The same procedure made and pressing the pedal, instructions say that minimal drop in vacuum is allowed, and it should return to almost same vacuum when depressing the pedal, this is where the vacuum disappears in my situation, two times brake pressed and the vacuum in container was all gone…where?

 

[curtis]

From the factory our vacuum line from the intake manifold to the brake booster has a one way check valve installed in the middle of the hose......so check that before you go taking stuff apart