lousy brakes

[bcarter]

My 1st gen brakes started to get really spongy, and I had to pump them before every turn back in July, so I replaced the master, put in new pads, bled them a million times, and hoped for the best. This weekend, no change, same lousy pedal, so I zoomed back to my parts car and pulled out the booster, and the proportioning valve, and put it in the race car, so we have new master, different booster, different valve, new pads, and new calipers 3 weekends ago...still lousy brakes. What can be left??? I am going to get the booster rebuilt, and see if I can find a new proportioning valve, but there's nothing left. We bled the brakes before every race, and no air...

What the heck is up?

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G. Brooke Carter
# 10 Challenge Car
Calgary, Alberta

[Jim Innella]

Just drained all the brake fluid out of my IT7.When I refilled and bled the brakes I couldn't get them to feel right(spongy). I just took the car to Speedsource to have them do the job right. They tried to explain how to do it over the phone but brakes are something I won't mess around with. When they have time to work on them next week I will watch how they do it. I know I didn't answer your question except that there seems to be a special technique to get them right. My brakes were great before I worked on them. I am sure someone will have an answer before next week , but if not I'll get back to you.
Jim
IT7 #60

[dickita15]

check the runout in the rotors. they may be kicking back the pads too far.
dick

[bcarter]

New rotors...straight, no run out.

Adam at RX-7 Specialties figures it is possible for air to get into the system through the calipers, and not leak fluid out.. Seems strange to me, but I think it has to be air. I'm going to put my old calipers back in. I only changed them because I had some new ones, not because there were poor.

I guess don't fix it if it ain't broke !

[jayroc]

My 84 GSL is doing something similar. Could be the hoses. I'd take the opportunity to replace the hoses with steel braided.

[bcarter]

Already got them.....

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G. Brooke Carter
# 10 Challenge Car
Calgary, Alberta

[eh_tony!!!]

If you pump them once before you really get on them, do they firm up?? If so, I think you might have an issue with (as previous poster said) the pads backing off too much. This is pretty much standard issue for us with Fiats, and I heard the VW guys use shims. Anyway, had a 510 that did this as well, and it was a bent spindle. One other thought, have a bud look at the firewall when you puch the brakes as hard as you can. I have heard of firewall flex causing this.

[jjohnston10]

Did you bench bleed the MC?
Also, if it was a remanufactured MC rather than a new one, there is a good chance that the "new" one is also bad. I'v got several bad "new" MC's over the years and the parts stores are used to getting them back.
Also did you get the correct MC for your car? (disk rear vs drum)

[Skid]

Is your parking brake still attached? I heard keeping the parking brake attached and properly adjusted helps firm the pedal... anyone able to explain this?

[bcarter]

OK, I agree that it is probably the MC. I went back to the car after 24 hours, and there was NO pedal at all. Must be air. There is no loss of fluid, we bench bled the master, bled the brakes before every race, and spent half of each race keeping the pedal up. Get's confusing, all that pumping, heel-toeing, braking etc. Actually went off once with my foot caught between pedals.

No parking brake.

I have the solution. I am replacing everything !

New MC from Mazda, not rebuilt. Getting the vacuum booster rebuilt. Trying to find a new proportional valve. Then with a pressure bleeder, at HIGH psi, I will go through the whole system, going back to my old (and functioning) calipers, one by one until I can get a pedal.

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G. Brooke Carter
# 10 Challenge Car
Calgary, Alberta

[backformore]

Hope all that part replacement works. Had a similar problem with my first gen. I think a change of pads was the problem and as such the solution.

Now I have a similar problem with my second gen. Been that way since i bought the car. It would be great if someone could provide a definitive solution or explanation. Anyone??

Rory

PS The brakes on my TurboII street car were exceptional (feel). Does the conversion to race setup, i.e. no parking brake, replacing stock proportioning valve with adjustable, etc., create the soft lack of feel?

[bcarter]

OK, I isolated the master cylinder by putting three crimped lines in, and the pedal was hard. Then I attached the proportioning valve, and the left front brake line, (the three lines from the MC), and got a good pedal, then I changed all four calipers, and bled the stupid system about 5 times, including the Wildwood bias valve by my seat, and did the system with just back brakes, then with all brakes. Also kept the front and back separate during different bleeding sessions, AND STILL HAVE LOUSY BRAKES. I disconnected the vacuum from the booster, and drove around the block, and altho it was hard to stop, I had no pedal fade. Attached the vacuum again, and the pedal dropped 2 - 3 inches, and got soggy. Can't race without the booster, not enough stop power without Superman foot. What the $#%^$#@#$% is the problem? Is there some sort of MC problem I don't know about? It is a NAPA "new" MC. Booster was checked at "brake booster re-build specialist" and OK'ed. AAARRRGGGHHH!

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G. Brooke Carter
# 10 Challenge Car
Calgary, Alberta

could it beeeeee, sound like the assist is working but will it work properly with low manifold vacume?. check vacume line for leaks, at this point have to try everything.

[This message has been edited by 7'sRracing (edited September 18, 2002).]

[B90278]

WHAT BRAKE PADS DO YOU USE, IS THIS DRUM OR DISK REAR.HOW LONG HAVE YOU BEEN RACING THE CAR?YOU MAY NOT HAVE RUN OUT LIKE DICKITA 15 SAID BUT IF THE CALIPERS ARE FLEXING TO MUCH FROM WEAR IT WILL KICK THE PADS BACK AND THEY WILL WEAR AT ANGLES WHICH WILL ALSO FEEL SPONGY CAUSE OF ONLY PARTIAL INITIAL CONTACT

my cars fixed Bernardo, see you soon

[bcarter]

Yikes... well, the rear rotors are straight, no run-out. I run Hawk Blues on the front, and relatively stock pads on the rear, otherwise too much rear brake. Looks like very even wear, but I will check again.

As for the vacuum, if here was a hole, I would have less vacuum, therefore a harder pedal, due to less mechanical advantage. I think I have almost too much.....

[itsrotary7sd]

There is a one way check valve in the vaccume line running to the brake booster. Make sure it is pointed in the right direction. I don't have the manual with me so I can't look it up.

[bcarter]

I don't see a valve in the line, where would it be...this is a first gen right!

[Weaver7]

I'm having the same trouble with my 1st gen. coming to the end of the back stretch at Watkins Glen my pedal goes to the floor although I have some stopping power it truly isn't all there. If I pump it a couple of times the pedal does come back but is still soft. I to have replaced everything and it seems to be better after I bleed them i.e if I bleed them in the AM before we go out they are soft but better. If I went out in the same day later on the pedal starts hitting the floor again. I wish someone could give me an answer to this anoying problem. This weekend I'm going to check the lines running to the booster. Any help would be GREATLY appreciated.

[bcarter]

Last race weekend coming up. If I don't smack a wall and destroy the car, I have all winter so do this.

I have ordered a new booster, a new master, a new proportioning valve, and new brake lines from Mazda, all coming in from Japan. I know it's not the calipers, because I have changed all 4, and have the same problem. I know it's not the steel braided brake lines as well, so there is nothing left. The rotors run true.

Solution...replace EVERYTHING !!! If that doen't work, I'm gonna race a BMW.....

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G. Brooke Carter
# 10 Challenge Car
Calgary, Alberta