I know this has been covered a bunch of times but i want some opions here.
I had my brake system completely dissasembled (92 DX, GSR booster and master, ITR brakes). The only thing left where the lines running to the back. i reassembled eveything, bleed in the correct order, checked for leaks while doing so and eveything seemed great.
The pedal had almost zero travel with the car shut off, it was rock hard.
I started the car and the pedal goes soft.
so i figured i must still have air trapped, bled again, same deal again.
Friend suggested bleeding with the car running, did that, same thing.
Now, with the car running and me pumping the brakes, the pedal does not get any stiffer.

After leaving the car alone for 3 days, today the pedal goes to the floor with the car off, when before it was stiff with the car off And if i pump the pedal it does not go stiff. Same deal with the car running.
There is no sign of fluid loss, and no leaks anyhwere.

What the hell is my problem here. bad boost, bad master?
I never bench bled the master when i put it back in, and all the fluid did drain out of it while it was sitting (still attached to the booster but i doubt that matters). should i bench bleed it?
all i want to do is drive my car again
It;s been about 10 months of driving a Suzuki Samurai, HELP lol

 

It's bad news to drain the MC. I would check out a friend's to see if that's your problem.

My brakes suck when I'm putting around town. I attribute that to my booster doing its job too well. With the car off there's no vacuum in the crankcase, so no booster assist. Similar deal at high rpm (pretty much at atm. pressure). Check out the MC first, though.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by zc911 &raquo;</TD></TR><TR><TD CLASS="quote">GSR booster and master, ITR brakes</TD></TR></TABLE>

Wouldnt this be your problem?

 

na, GSR and ITR setup is almost the same. It was working excellent before taking everything apart

GSpeedR
thanks for the suggestion, i guess i'll give the MC a try and see what happens.
Is there any chance it;s the booster?

 

Did you replace the seal between the booster and master when you took it apart?

 

i never seperated the booster from the master. I took it out as one piece

 

A bad master is the most likely cause of your problems. The first thing you need to do is start the engine and press on the brake pedal without pumping with moderate force for a minute or so. If it slowly goes to the floor, then your master cylinder is junk. It doesn't mater if the brake lines have air; if the pedal slowly goes down the master is bad.

The reason you can have a bad master with no fluid leaks is that there is an internal fluid re-circulating channel in the master. A seal prevents the escaping fluid from reaching the booster, and directs the fluid along a passageway on the top of the cylinder back to the reservoir.

You don't need to bleed the master when replacing it. Most air will bubble out the top into the reservoir; the rest will go down the brake lines.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GSpeedR &raquo;</TD></TR><TR><TD CLASS="quote">It's bad news to drain the MC. </TD></TR></TABLE>
When I did my rear disc conversion I got a GSR BB & MC which was completely drained. Installed it and bled the whole system with a vaccula at each corner and my MC is perfectly fine???

I do agree though that a slowly sinking pedal is either a fluid leak which you have eliminated or a faulty MC... replace the MC if you are positive that there are no leaks.

If you had air in your lines then most likely your pedal would be low to begin with before you even touch it and you would have to pump the pedal to get some pressure... this is the symptom of air in the lines.

 

Only three more things to check. Master, booster or checkvalve. I can't remember what presents with what symptoms. I would look for a bad master. If it is a bad master, make sure the fluid hasn't gotten on the diaphram of the booster. If so, it may have damaged the booster assembly.

If you do a search from long ago, with me as the author, you will find the complete diagnosis from the Helms manual. I am away from the house right now so I ccouldn't check in the book.

 

BTW, did you change the proportioning valve or did you keep the DX one?

We replaced everything in out 97 DX Hatch racecar- to 99 Si MC/Booster (from junkyard with MC attached to booster and drained), 99 Si Prop Valve, 99 Si brakes and Calipers- (which are now 12.1 in. wilwoods) The Junkyard MC/Booster still works perfectly after 8 races...

Good luck.

 

Have you thought of adjusting the brake booster? Could be dangerous if that isn't the problem though, don't want to cover up the real problem.

 

thaniks for all the suggestions guys i have been sick so i havnt looked at the car in a few days. I will do the pedal test today and see what happens
thanks again for all the suggestions, i hope it is jsut the MC