NightKid#2

iTrader: (3)

This problem on my 99 TA that just wont go away and its driving me nuts. I had the brakes professionally bled,all lines check out ok and replaced the pads. replaced the rear rotors. replaced the front calipers. Then had the brakes bled again and again. The problem is very strange, when I apply the brakes softly the brakes are fine for the most part there have been two or three occasions. When I apply the brakes heavily the peddle (only half of the time and more so at speeds over 50mph) drops a centimeter or so and the car will sway back and forth or yank me to one side, like it has unequal pressure on each rotor. I thought the calipers were locking up or over extending on one side. So after doing what I said I've done the problem still remains. I got to thinking that the ABS might be failing so I got up to 35mph and slammed on the brake and to my suprise my tires fully lock-up, never felt the peddle vibrate indicating the ABS was even trying and the "ABS INOP" didn't light up.

SO I just wanted to see if
A.Someone has anymore info on how the ABS system fails and acts when failing, repair it, remove it.
B.Someone has any other thoughts on the matter and what it might be

Thanks guys, JR

7901 WS6

iTrader: (6)

Maybe you have a bad Brake Proportioning valve. Thats what it sounds to me.

NightKid#2

iTrader: (3)

Is their anyway to check it? Your taking about the valves in the brake master cylinder right?

NightKid#2

iTrader: (3)

Priced a new master brake cylinder $106.
Before I go spend that cash anyone have any other thoughts on the problem?
Again I did some harsh stops trying to get the ABS to kick in.
I locked up my tires every time and the only light that came on was the "low traction" light. I'm still thinking ABS problem.

7901 WS6

iTrader: (6)

It would not be in your master cylinder. its underneath it in the lines. Your brake line come out of the master and go straight to it. I havent looked at my car yet to tell you exactly where it is but maybe price that out and see if its something you can do. Also make sure your brake calipers pins are greased well so they can slide.

99345hp

I am pretty sure the proportioning valve is in the ABS unit in our cars. The brake proportioning valve pretty much only regulates pressure between the front and the rear. Im trying to think of what this problem could be, but you have pretty much checked everything except one thing.

With the wheels off the car press the brakes several times.
Squeeze a flat head screwdriver between the pad and rotor in the front.
Try to compress the calipers, and note if there is a difference in the two sides.
If one side is hard to compress then you probably have a hose that is closing up.
If it were my car, being that you have replaced everything else, then i would go ahead and replace both front hoses. They arn't that expensive, and easy to replace.

NightKid#2

iTrader: (3)

That is a response I'm looking for. I will give it a shot as I was thinking about replacing the front lines anyway. I read up on the ABS and its problems last night after my last post. I will try that and then I am going to try and unplug the ABS unit. I know the proportioning value is in there and in will be giving me 50/50 brake distribution but it should let me know if it is interfering with my braking. Hell as I said before the ABS is not even working anyway. If I find its the ABS unit or the brake lines all post back my findings. If its the ABS though its getting deleted right away as i feel i don't need it, as i've never lock up my wheels in a panic situation or on any turns while braking in any car I've driven.

Thanks for your help guys, JR

99345hp

If you delete the ABS system, just make sure you get a proportioning valve out of a non abs car, or buy an adjustable one. I think Summit sells them, or maybe some of the sponsors?

NightKid#2

iTrader: (3)

All do it correctly if i delete it. I was looking at sjm manufacturing's kits as a line lock sounds good too. All post again in a couple hours with what I fine as I'm off to solve it once again .

NightKid#2

iTrader: (3)

I was 100% right on the money. Disconnected the ABS plug at the valve box and went out doing about 15 hard stops ranging from 35 to 75mph and she stopped straight and true. Halfway back home I plugged the ABS plug back in and the first stop I tried (at 60mph) she swayed back an fourth really bad. Got back out disconnected the plug again did about 7 more stops and never had a problem. And I must say 50F/50R bias doesn't feel to bad when stopping, though I know it could be better.
I laid on the brakes hard a couple of those times on a dusty road and the tires never lock up so I'm 100% ready to rip that ABS crap right out of the engine bay. I will say that I have corvette wheels on my car and the difference in the diameter of the tires was causing the problem. Now all I have to do it get rid of the three lights that come on because of unplugging it lol.

Dose any one have the wiring manual with a diagram of the ABS wiring? I know that the lights are triggers by probably one wire needing to be grounded or a 12v supply, I love reading wiring diagrams . Anyone want to supply me with them ? All do a write-up for all the guys that have the lights on if I can get hold of the diagrams.

Thanks for all the help guys, JR

99345hp

Im glad that you found the problem. Without removing the whole abs unit, you still have the proportioning valve in place. So, while it is unplugged, it is still there doing its job of biasing pressure between front/rear.