Uncontrollable breaking?
10-08-2010, 12:21 AM
#1
Uncontrollable breaking? Car is a 02 Trans Am. I picked it up as a roller and we put it back together, and got it running. It came with new brakes all around. The rotors are drilled/slotted, and it looks like the pads are Hawks.
The problem that its doing is that under hard braking, the car is all over the road. It doesn't stop straight. It feels like if you just slam the brakes, you will loose control of the car..At first we thought it was the suspension. The car had QA1s in the front, and Comp Engineering drag shocks in the back. I wanted to take those out anyways because this isn't a drag car..We put the stock DeCarbons back on, and problem is still there.
We did try bleeding the brakes when we first got the car running, and all we got was a little bit of air out of one caliper.
The current ideas that we are thinking are:
One caliper is sticking
Air still in the lines somewhere
Bad proportional valve(ABS module)
Even before I drove the car and knew about the problem, I purchased a new Z06 brake kit upgrade..So I have new calipers, pads, and rotors going on all around. If we change those and the problem is still there, I guess that will rule those items. But what do you guys recommend I look at?
The problem that its doing is that under hard braking, the car is all over the road. It doesn't stop straight. It feels like if you just slam the brakes, you will loose control of the car..At first we thought it was the suspension. The car had QA1s in the front, and Comp Engineering drag shocks in the back. I wanted to take those out anyways because this isn't a drag car..We put the stock DeCarbons back on, and problem is still there.
We did try bleeding the brakes when we first got the car running, and all we got was a little bit of air out of one caliper.
The current ideas that we are thinking are:
One caliper is sticking
Air still in the lines somewhere
Bad proportional valve(ABS module)
Even before I drove the car and knew about the problem, I purchased a new Z06 brake kit upgrade..So I have new calipers, pads, and rotors going on all around. If we change those and the problem is still there, I guess that will rule those items. But what do you guys recommend I look at?
10-08-2010, 01:19 AM
#2
When I did all the extensive motor, k-member, all that jazz swap on my car... I had the same problem with unpredictable braking. I had tried to bleed all the lines myself. Long story short, I took it to a brakes place (Only time my car has been to a shop) and they bled them more, and now they are perfect.
I guess long story short, they need to be bled ALOT. Try that maybe?
As far as I know, Porportioning valve is front to rear braking.
Also, do you still have ABS installed? If you do, and you are using different size tires like me (26" front 28" rear), you could have problems as well.
I guess long story short, they need to be bled ALOT. Try that maybe?
As far as I know, Porportioning valve is front to rear braking.
Also, do you still have ABS installed? If you do, and you are using different size tires like me (26" front 28" rear), you could have problems as well.
10-09-2010, 09:54 PM
#4
Possibilities are:
Collapsed brake hose
Frozen caliper piston
Stuck slide pins
It is also possible that you have air in one of the calipers or air in the line going to one side. I would pull everything apart, check the pistons and slide pins, and then do a complete bleed of the system again.
Also, remember a bad alignment can also cause a pull during braking.
Collapsed brake hose
Frozen caliper piston
Stuck slide pins
It is also possible that you have air in one of the calipers or air in the line going to one side. I would pull everything apart, check the pistons and slide pins, and then do a complete bleed of the system again.
Also, remember a bad alignment can also cause a pull during braking.
10-09-2010, 10:28 PM
#5
Did you pressure bleed the ABS module ? Ive read that alot of people are having problems with that. You can either take it to a good mechanic or buy a $60 tool for pressurizing your brake system. there was a link to one in i believe the lt1-lt4 section
10-10-2010, 03:46 PM
#6
Possibilities are:
Collapsed brake hose
Frozen caliper piston
Stuck slide pins
Collapsed brake hose
Frozen caliper piston
Stuck slide pins
We had the car aligned and it still does the same thing.
No we never did anything to the ABS module. I will look into that. Now that I think about it, I dont think I ever felt ABS kick in with this car?
10-10-2010, 08:46 PM
#7
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Does the car have any extreme rear suspension mods?
Like a short torque arm? Something that might make the
rear lift on braking because they tried too hard to make
it plant on launch?
If the front really dives on braking you might also be
seeing a caster change? Maybe the alignment you get
sitting there, is not the alignment you have on hard
braking. Too, these cars do wear out front suspension
and you have to replace assemblies (not just a ball
joint). If you have a lot of play, you could get aligned
OK but have the toe be "situational". Do you feel any
weirdness when you roll forward, brake, roll rearward,
brake, roll forward? Front end clunks? There's some
thing of this sort going on with mine, the steering feels
different afterward if I brake hard in reverse. I don't
think it's my K-member (those welds seem to be holding)
but may be where the A-arm bolts to it or something.
Anyway, what looks and feels tight to you may not be
quite tight enough for hard-braking a fat *** sled.
Like a short torque arm? Something that might make the
rear lift on braking because they tried too hard to make
it plant on launch?
If the front really dives on braking you might also be
seeing a caster change? Maybe the alignment you get
sitting there, is not the alignment you have on hard
braking. Too, these cars do wear out front suspension
and you have to replace assemblies (not just a ball
joint). If you have a lot of play, you could get aligned
OK but have the toe be "situational". Do you feel any
weirdness when you roll forward, brake, roll rearward,
brake, roll forward? Front end clunks? There's some
thing of this sort going on with mine, the steering feels
different afterward if I brake hard in reverse. I don't
think it's my K-member (those welds seem to be holding)
but may be where the A-arm bolts to it or something.
Anyway, what looks and feels tight to you may not be
quite tight enough for hard-braking a fat *** sled.
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10-10-2010, 08:46 PM
#8
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Does the car have any extreme rear suspension mods?
Like a short torque arm? Something that might make the
rear lift on braking because they tried too hard to make
it plant on launch?
If the front really dives on braking you might also be
seeing a caster change? Maybe the alignment you get
sitting there, is not the alignment you have on hard
braking. Too, these cars do wear out front suspension
and you have to replace assemblies (not just a ball
joint). If you have a lot of play, you could get aligned
OK but have the toe be "situational". Do you feel any
weirdness when you roll forward, brake, roll rearward,
brake, roll forward? Front end clunks? There's some
thing of this sort going on with mine, the steering feels
different afterward if I brake hard in reverse. I don't
think it's my K-member (those welds seem to be holding)
but may be where the A-arm bolts to it or something.
Anyway, what looks and feels tight to you may not be
quite tight enough for hard-braking a fat *** sled.
Now if the ABS is messed, that could really squirrel it up.
On stock cars the ABS is what does the proportioning.
If it's got ABS deleted, or ABS faulted and the light
taped over, etc. you may have a proportioning problem.
I'd think you would know if the rear is locking up. But
not all tires make noise, mine don't at all when I spin.
Might have a buddy do chase vehicle duty, see if he
can notice wheel hop or lockup. I saw a Mustang go
into bad hop on the I-95 once while trying to panic-stop,
looked like he was having some fun with that.
Like a short torque arm? Something that might make the
rear lift on braking because they tried too hard to make
it plant on launch?
If the front really dives on braking you might also be
seeing a caster change? Maybe the alignment you get
sitting there, is not the alignment you have on hard
braking. Too, these cars do wear out front suspension
and you have to replace assemblies (not just a ball
joint). If you have a lot of play, you could get aligned
OK but have the toe be "situational". Do you feel any
weirdness when you roll forward, brake, roll rearward,
brake, roll forward? Front end clunks? There's some
thing of this sort going on with mine, the steering feels
different afterward if I brake hard in reverse. I don't
think it's my K-member (those welds seem to be holding)
but may be where the A-arm bolts to it or something.
Anyway, what looks and feels tight to you may not be
quite tight enough for hard-braking a fat *** sled.
Now if the ABS is messed, that could really squirrel it up.
On stock cars the ABS is what does the proportioning.
If it's got ABS deleted, or ABS faulted and the light
taped over, etc. you may have a proportioning problem.
I'd think you would know if the rear is locking up. But
not all tires make noise, mine don't at all when I spin.
Might have a buddy do chase vehicle duty, see if he
can notice wheel hop or lockup. I saw a Mustang go
into bad hop on the I-95 once while trying to panic-stop,
looked like he was having some fun with that.
10-15-2010, 06:51 AM
#9
Thanks for all the tips. We have been looking into it. We tryed to bleed the fronts, and got very little air out. Then we tryed to bleed the rears and we got nothing out..Very little fluid or air. Looks like the rear brakes aren't even working, at all. So thats what has been causing the bad breaking..Only the front brakes work.
Now we have to see what is going on with that. When I first got the car, we noticed that somethign weird was going on with the lines going to the ABS unit. It looked like someone had messed with the lines, rerouted them or pushed them over or something as they were hitting the steering shaft. Maybe someone changed the ABS unit at some point, or had removed ABS and then put it back on?
Now we have to see what is going on with that. When I first got the car, we noticed that somethign weird was going on with the lines going to the ABS unit. It looked like someone had messed with the lines, rerouted them or pushed them over or something as they were hitting the steering shaft. Maybe someone changed the ABS unit at some point, or had removed ABS and then put it back on?
10-21-2010, 10:22 AM
#11
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Thanks for all the tips. We have been looking into it. We tryed to bleed the fronts, and got very little air out. Then we tryed to bleed the rears and we got nothing out..Very little fluid or air. Looks like the rear brakes aren't even working, at all. So thats what has been causing the bad breaking..Only the front brakes work.
Now we have to see what is going on with that. When I first got the car, we noticed that somethign weird was going on with the lines going to the ABS unit. It looked like someone had messed with the lines, rerouted them or pushed them over or something as they were hitting the steering shaft. Maybe someone changed the ABS unit at some point, or had removed ABS and then put it back on?
Now we have to see what is going on with that. When I first got the car, we noticed that somethign weird was going on with the lines going to the ABS unit. It looked like someone had messed with the lines, rerouted them or pushed them over or something as they were hitting the steering shaft. Maybe someone changed the ABS unit at some point, or had removed ABS and then put it back on?
Last edited by 94BlueZ28; 10-21-2010 at 10:40 AM.
10-22-2010, 04:34 PM
#13
We do know that the rear brakes aren't working..We had the car on a lift and when we were pressing on the brakes the rear tires were still spinning. Then when we tried to bleed them barely anything came out. So what do I do now? Do I try to bleed teh ABS unit, or replace it? Anyway to check if the unit itself is bad?
10-22-2010, 04:45 PM
#14
I'm sorry Jimmy I didn't know you did the obvious. I don't know much about the ABS block itself except I myself would take it to the dealer unless you know someone with a TECHII device to scan the car AND bleed the ABS unit. The TECHII costs upwards of 5K so not many people have one laying around. The dealer can tell you what's wrong; you can decide what to do after that. They may charge between $75-$150 to give you the answer.
10-23-2010, 10:37 PM
#15
We do know that the rear brakes aren't working..We had the car on a lift and when we were pressing on the brakes the rear tires were still spinning. Then when we tried to bleed them barely anything came out. So what do I do now? Do I try to bleed teh ABS unit, or replace it? Anyway to check if the unit itself is bad?
If you're bleeding the rear brakes and barely any fluid is coming out and they do not work, that leaves two possibilities. You either have a crushed line or collapsed hose somewhere, or the ABS unit is bad.
I would start by inspecting all the hard lines for kinks or damage, and then check the brake hoses. There are three hoses to check the the rear brakes - the one that goes from the chassis to the rear axle, and the hoses that go to each caliper. If you remove a hose from the hard line, push the brake pedal, and fluid shoots out, then you have found your problem. If not, I'd say its the ABS unit itself thats the problem.
10-26-2010, 12:55 AM
#17
huh interesting. i had a collapsed hard line on my rear driver side that i never really thought too much about, it wasnt collapsed all the way. before i lowered it, it would wander all over the place then after i lowered it the problem went away so i chopped it up to extreme nose dive and alot of weight transfer to the front wheels which would follow the uneveness of roads which would cause it to wander, man....how wrong i was. oh well, i dont have that car no more
