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Discussion Starter · #1 ·
The better part of today was spent trying to bleed the brakes on my newly acquired GT. Lets just say that things are not going well. The brakes had been pointed out as being weak before I bought the car. The master cylinder and the vacume line to the boost pump had been replaced by the previous owner. When I recieved the car the brakes were bad. I could stop the car with the brakes but had to down shift to help it out a bit and an emergency stop would get scary fast.

When the pedal was depressed it would go 1/2 to 2/3 of the way down then get hard. The first part of the pedal movement felt choppy. (like a rubber seal or boot rubbing against something) It also felt unassisted so the booster was the first suspect. The check valve was first verified as good. The boost pump had vacume when the valve was removed so I spoke with the guys at OGTS to get an opinion. They felt that the boost pump was good and recomended adjusting the rear acentrics and see if things improved. The adjusters were a bit off but there was still no notable difference in performance. This gets us to this morning. OGTS recomended bleeding the system and putting in new fluid if the brakes didn´t improve. First thing this morning I hit up the local parts place and bought decent fluid and a self bleeding kit as everyone else has to work for a living. The first thing that I started with was to drain the reservoir down so that only a small amount of fluid filled the bottom. I filled it back up with the good stuff then the "self bleeding" kit was installed to the right front caliper and we´re off to the races. I started there because I felt this would get any air traped in the front of the system. I thought that I was allowing air into the system this morning while trying to bleed the brakes by myself, but when I got a neighbor to help in the evening things did not improve. The pedal was described as inconsistant and I got alot of air. Now I need help. Could the air be coming in through the reservoir seal at the master cylinder? Or could the master cylinder need rebuilt? I am at a loss now.


Discussion Starter · #2 ·
To add to this...

there was no fluid leaking at any of the lines or banjo fittings and the front calipers were also checked for movement before bleeding the system. The e brake also works well.

Discussion Starter · #3 ·
I had a very similar problem myself, I rectified them by doing a combo of the following:
I started with the rear wheel cylinders rebuilding had to hone them because of rust and pits, put in the rebuild kit from OGTS. Brakes got better but not noticibly.Looked at the front brakes turned and trued the rotors replaced the rubber lines (from OGTS)checked the movement of the Calipers looked the cups over for distortion or rotted rubbers , everything seemed fine there but still sloppy brakes. Next was the Master Cylinder , got the rebuild kit from OGTS pulled my master cylinder took it apart it was pooped out . I tried to clean it up with solvent and a hone for two hours but the rust had killed it . There were some places with enormous pits that the fluid would just squeeze by terrible.So I went to a nearby auto parts store they found me a master cylinder for a 70 GT (I think it was $35) I put it on .I did buy the resevoir seals from OGTS though, these are important! Then i pressure tested my brake lines to make sure no pinholes in the lines. Now i figured i had a real solid brake system so i got two cans of brake fluid and began bleeding and everything worked fine. By the way that Master cylinder is real fun to get out. And if you decide to hone anything make sure you have a caliper around to measure so you don´t take too much out! Also you really do not want to mix brake fluids so I would recommend a dry start after flushing your system this way you can do a pressure test .(may not be right this is just the way i do it)
Hopefully this will give you an idea of what to look at to figure out what´s wrong with your brakes.
Good Luck! :D

Discussion Starter · #4 ·
Brakes are one of my "special interest items"... ok, I´m anal brakes, so I´ll give this a go.

First, if you haven´t been there go to : http://www.tgsi.com/brakes.html

I´ll start out here by saying that trying to "patch up" brakes isn´t a good idea. You may get this problem fixed, but next week or next month, something else will get you... when you least expect it. Ok... since I know most people will want to patch stuff up until all the parts arrive from OGTS, here goes.

There could be a bunch of potential problems, but for now I´ll just address two. The master cylinder and brake fluid.

The master cylinder is the next most likely culprit. If the seals inside have hardened, or rust has attacked, they will "bypass". Which means that you simply won´t put pressure into the lines. With the lines open for bleading, it will push some fluid, but the brakes won´t work correctly. Another problem is the rear seal of the master cylinder. If the rear seal leaks, then it will suck air into the brakes. The only way you will know is to take everything apart. (By the way, if the rear seal leaks, fluid will "disappear" without any external signs of a leak at the "normal" leak points.)

I mentioned rust... If the car has been sitting for a while, it´s probably bad news. Brake fluid absorbs moisture, and the insides of the master cylinder, calipers and rear wheel cylinders will RUST. I´ve seen them so bad that I couldn´t punch the pistons out of the wheel cylinders with a hammer (big) and a punch.

Racer types drain and refill our brake fluid at least once a year. I do this every time I change brake pads which is about every 6 hours of racing.

So everyone should go out this week-end, drain, flush and refill the brakes on your Opel. (Told you I´m anal about this.) This is going to take some work. Having the right stuff will help a lot. Get two long pieces of clear plastic tubing.. at least 4 feet long and two clear plastic containers. For now, don´t wory about air in the system. Hook the clear tubes to both rear bleeders and run the tubes into the clear containers. Now that you are set-up, open up both bleeders and pump all the fluid out. (I like a clear container so I can examine the old stuff).

Once you´ve got the rear empty, go to the front and empty that half of the system. Fill the system up with fresh brake fluid and do the whole thing again. Don´t wory about pumping air through because it doesn´t matter at this point. You should do this at least twice to get the system flushed out well. Flushed out well means that you are getting clean clear fluid in your containers at all four corners of the car. (If it doesn´t ever come through clean, it´s time for a complete system rebuild... and in keeping with my "analness", it´s probably time for a system rebuild any way.)

Now, since the system is full of air, it´s going to take a lot of effort to get all the air out. Fill up the reservoir , and start bleeding at the right rear; then the left rear; then the right front; and then the left front. The first time around you´re not going to get all the air out at any corner. You´ll need to go around the car at least two times, and probably three, four, or more times. As you go from wheel to wheel, be sure to check the fluid reservoir to be sure it is has plenty of fluid. If the reservoir runs dry, you´ll have to start over. Once you´ve gone to all four courners (in succession) and have gotten no more air out, do all four courners one more time to be sure. For the "one more time", take out about 1 oz more at each corner.

Although I have just ruined your Saturday, and probably most of Sunday, your fluid will be good for another year... ok, at least a couple of years.
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