Brakes MALFUNCTION/SAFETY ISSUE
08-11-2013, 01:52 PM
#11
08-11-2013, 02:21 PM
#12
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It probably wouldn't have been a huge deal if it hadn't somehow opened the fluid line.
One second brakes, the next it went to the floor. And going down a steep grade to intersection/stop sign at 50mph was no fun.
Luckily I didn't panic. Just pumped the **** out of the brakes over and over again, geared down manually really hard, and put my foot to the floor the last part of it.
I got stopped before hitting the intersection, and thankfully there was no one in front of me.
Just glad I hadn't switched vehicles with my gf, because all she knows is gas, brake, P, R, and D. Any less experienced driver/defensive, non-aggressive, etc. would likely have had a deadly accident. I did everything I could do to avoid it. Again, another reason I like to have an actual parking brake lever. But our e-brake works that way if you tap up on it while moving at speed. Only problem was my emergency brake was not engaging at all anyway because the rear caliper was the problem.
One second brakes, the next it went to the floor. And going down a steep grade to intersection/stop sign at 50mph was no fun.
Luckily I didn't panic. Just pumped the **** out of the brakes over and over again, geared down manually really hard, and put my foot to the floor the last part of it.
I got stopped before hitting the intersection, and thankfully there was no one in front of me.
Just glad I hadn't switched vehicles with my gf, because all she knows is gas, brake, P, R, and D. Any less experienced driver/defensive, non-aggressive, etc. would likely have had a deadly accident. I did everything I could do to avoid it. Again, another reason I like to have an actual parking brake lever. But our e-brake works that way if you tap up on it while moving at speed. Only problem was my emergency brake was not engaging at all anyway because the rear caliper was the problem.
Last edited by ThunderDent; 08-11-2013 at 02:30 PM.
08-12-2013, 09:58 AM
#13
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Well, so far the word from the service dept working on the car is, there are no bolts to be found anywhere. So either they have worked their way completely out, were never there to begin with, or it could have been tampered with I suppose.
I talked to service mgr at my local dealership which put everything on, and all was put on an torqued to spec. Again, I've driven nearly 8,000 miles since that work was completed.
So the bolts must have backed out. I wouldn't think you could get up in there and unscrew/loosen them without the wheel off.
So if what happened is the bolts backed out, why did it happen?
They are stock calipers. Stock pads. Adams rotors (slotted/dimpled), stainless braided lines.
The tech said the piston/caliper was beat up and had to be replaced. Along with new pads. Rotors and lines were fine. He said the brake fluid drained out when the piston blew out.
So did the rotors cause enough vibration to loosen the bolts?
My other question is... is there not 2 master brake cylinders. One front & one back? That way if a rear line bleeds out you still have the front brakes? I had NO brakes!
People have told me that's been a law since the 70s.
I talked to service mgr at my local dealership which put everything on, and all was put on an torqued to spec. Again, I've driven nearly 8,000 miles since that work was completed.
So the bolts must have backed out. I wouldn't think you could get up in there and unscrew/loosen them without the wheel off.
So if what happened is the bolts backed out, why did it happen?
They are stock calipers. Stock pads. Adams rotors (slotted/dimpled), stainless braided lines.
The tech said the piston/caliper was beat up and had to be replaced. Along with new pads. Rotors and lines were fine. He said the brake fluid drained out when the piston blew out.
So did the rotors cause enough vibration to loosen the bolts?
My other question is... is there not 2 master brake cylinders. One front & one back? That way if a rear line bleeds out you still have the front brakes? I had NO brakes!
People have told me that's been a law since the 70s.
08-12-2013, 10:20 AM
#14
AudiWorld Super User
Yes, independent front and rear master cylinders...
Well, so far the word from the service dept working on the car is, there are no bolts to be found anywhere. So either they have worked their way completely out, were never there to begin with, or it could have been tampered with I suppose.
I talked to service mgr at my local dealership which put everything on, and all was put on an torqued to spec. Again, I've driven nearly 8,000 miles since that work was completed.
So the bolts must have backed out. I wouldn't think you could get up in there and unscrew/loosen them without the wheel off.
So if what happened is the bolts backed out, why did it happen?
They are stock calipers. Stock pads. Adams rotors (slotted/dimpled), stainless braided lines.
The tech said the piston/caliper was beat up and had to be replaced. Along with new pads. Rotors and lines were fine. He said the brake fluid drained out when the piston blew out.
So did the rotors cause enough vibration to loosen the bolts?
My other question is... is there not 2 master brake cylinders. One front & one back? That way if a rear line bleeds out you still have the front brakes? I had NO brakes!
People have told me that's been a law since the 70s.
I talked to service mgr at my local dealership which put everything on, and all was put on an torqued to spec. Again, I've driven nearly 8,000 miles since that work was completed.
So the bolts must have backed out. I wouldn't think you could get up in there and unscrew/loosen them without the wheel off.
So if what happened is the bolts backed out, why did it happen?
They are stock calipers. Stock pads. Adams rotors (slotted/dimpled), stainless braided lines.
The tech said the piston/caliper was beat up and had to be replaced. Along with new pads. Rotors and lines were fine. He said the brake fluid drained out when the piston blew out.
So did the rotors cause enough vibration to loosen the bolts?
My other question is... is there not 2 master brake cylinders. One front & one back? That way if a rear line bleeds out you still have the front brakes? I had NO brakes!
People have told me that's been a law since the 70s.
I'm glad you survived the ordeal, and as another poster posted here, new bolts should be used when repairs are made as they have a lock coating.
08-12-2013, 10:24 AM
#15
AudiWorld Super User
Bolt related--a question for you again.
As I said in my prior reply, I think you should review the prior work order when the brakes were installed. If the bolts are not in the work order and don't come in the Audi pad kit themselves, that would not generally follow standard Audi service protocol. The factory bolts all have Locktite on them--typically the blue colored stuff and seemingly manually applied on the rears specifically. This info is objectively determinable if you go back to the work order, and if need be have a parts counter person pull a current set of factory pads to see what comes with them if the bolts aren't separately invoiced.
As I also stated and still believe, if the bolts weren't Locktited (either by replacement or at least in refitting), that's a set up for them possibly coming out. On torquing, my guess is they weren't torqued either. Even w/ out new Lock rite, they wouldn't tend to come loose with decent torque, plus the old bolts and threads in practice tend to still have some residual Locktite on them that gums them up some and resists turning.
On the explanations you have so far, realistically who--besides perhaps you for a DIY job--is going to remember specifically that 8,000 miles and many repair jobs later, (other than basically restating it would be their "standard" approach? "Standard" or "normal" is not always the same as what actually happened. Having done the job enough times, you have to basically pause at that step, get a lock wrench into the pin into which the bolt tightens, and then proceed. You also need either Lock tite on hand (for that one thing), or new bolts. They sometimes come out without the need for the extra wrench given the accumulated road miles and vibration, but not typically on the way in. Toquing can be overlooked, especially if the job is interrupted, plus with the need now to cycle the parking brake motor along the way and while away from the wheel work area.
As I also stated and still believe, if the bolts weren't Locktited (either by replacement or at least in refitting), that's a set up for them possibly coming out. On torquing, my guess is they weren't torqued either. Even w/ out new Lock rite, they wouldn't tend to come loose with decent torque, plus the old bolts and threads in practice tend to still have some residual Locktite on them that gums them up some and resists turning.
On the explanations you have so far, realistically who--besides perhaps you for a DIY job--is going to remember specifically that 8,000 miles and many repair jobs later, (other than basically restating it would be their "standard" approach? "Standard" or "normal" is not always the same as what actually happened. Having done the job enough times, you have to basically pause at that step, get a lock wrench into the pin into which the bolt tightens, and then proceed. You also need either Lock tite on hand (for that one thing), or new bolts. They sometimes come out without the need for the extra wrench given the accumulated road miles and vibration, but not typically on the way in. Toquing can be overlooked, especially if the job is interrupted, plus with the need now to cycle the parking brake motor along the way and while away from the wheel work area.
08-12-2013, 10:34 AM
#16
AudiWorld Super User
A little different technical take here
First, it's one master cylinder overall. It has two chambers/circuits in line with each other.
Audi's have also been "dual diagonal" for ages. Thus, in the overall set up, the front left wheel is tied hydraulically to the right rear, and similarly the other two. Thus, losing a front brake is not hugely catastrophic like it used to be given where the biggest braking forces are. Plus, the diagonal approach (instead of linear front and back on same side) reduces the heavy pull that would otherwise result; that thinking pre dates modern ABS as a basic safely approach--goes all the way back to the Audi C1 in the early 70's. ABS cycling can now mask/reduce some of the pulling here too. As an aside, if you ever bleed a system like this manually and watch the fluid drop carefully, you will see how it affects the front or back part of the fluid reservoir sequentially even though you ae doing the same end of the car for each two steps.
But, the downside of the set up is in the scenario that happened--it didn't just take out the less important rears, but rather it took out fully half of the braking force on the car. At least until (and if) the brakes could be pumped enough to lock up the loose rear caliper piston and then get some pressure back to the diagonally opposite front one.
All this is unfortunate, but so far as I've suggested, I would be examining the bolts and how they were installed or reused most critically. Nothing else in here is saying there is a design question, or anything fundamentally different than other modern rear disk brake set ups from many a manufacturer.
Audi's have also been "dual diagonal" for ages. Thus, in the overall set up, the front left wheel is tied hydraulically to the right rear, and similarly the other two. Thus, losing a front brake is not hugely catastrophic like it used to be given where the biggest braking forces are. Plus, the diagonal approach (instead of linear front and back on same side) reduces the heavy pull that would otherwise result; that thinking pre dates modern ABS as a basic safely approach--goes all the way back to the Audi C1 in the early 70's. ABS cycling can now mask/reduce some of the pulling here too. As an aside, if you ever bleed a system like this manually and watch the fluid drop carefully, you will see how it affects the front or back part of the fluid reservoir sequentially even though you ae doing the same end of the car for each two steps.
But, the downside of the set up is in the scenario that happened--it didn't just take out the less important rears, but rather it took out fully half of the braking force on the car. At least until (and if) the brakes could be pumped enough to lock up the loose rear caliper piston and then get some pressure back to the diagonally opposite front one.
All this is unfortunate, but so far as I've suggested, I would be examining the bolts and how they were installed or reused most critically. Nothing else in here is saying there is a design question, or anything fundamentally different than other modern rear disk brake set ups from many a manufacturer.
Last edited by MP4.2+6.0; 08-12-2013 at 10:57 AM.
08-12-2013, 12:07 PM
#18
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Also, your ABS explaination correlates to what I experienced.
When I would pump the brakes I would get some braking, then it would be gone to the floor. So if it was alternating between FR/ LR (the good reservoir), and the other (RR/FL) was out, that's what was happening. I could use the brakes, but it was hard to the floor to do it. No hydraulic to it at all.
When I would pump the brakes I would get some braking, then it would be gone to the floor. So if it was alternating between FR/ LR (the good reservoir), and the other (RR/FL) was out, that's what was happening. I could use the brakes, but it was hard to the floor to do it. No hydraulic to it at all.
08-12-2013, 12:17 PM
#19
AudiWorld Super User
Yes, my bad, I forgot the diagonal setup....
First, it's one master cylinder overall. It has two chambers/circuits in line with each other.
Audi's have also been "dual diagonal" for ages. Thus, in the overall set up, the front left wheel is tied hydraulically to the right rear, and similarly the other two. Thus, losing a front brake is not hugely catastrophic like it used to be given where the biggest braking forces are. Plus, the diagonal approach (instead of linear front and back on same side) reduces the heavy pull that would otherwise result; that thinking pre dates modern ABS as a basic safely approach--goes all the way back to the Audi C1 in the early 70's. ABS cycling can now mask/reduce some of the pulling here too. As an aside, if you ever bleed a system like this manually and watch the fluid drop carefully, you will see how it affects the front or back part of the fluid reservoir sequentially even though you ae doing the same end of the car for each two steps.
But, the downside of the set up is in the scenario that happened--it didn't just take out the less important rears, but rather it took out fully half of the braking force on the car. At least until (and if) the brakes could be pumped enough to lock up the loose rear caliper piston and then get some pressure back to the diagonally opposite front one.
All this is unfortunate, but so far as I've suggested, I would be examining the bolts and how they were installed or reused most critically. Nothing else in here is saying there is a design question, or anything fundamentally different than other modern rear disk brake set ups from many a manufacturer.
Audi's have also been "dual diagonal" for ages. Thus, in the overall set up, the front left wheel is tied hydraulically to the right rear, and similarly the other two. Thus, losing a front brake is not hugely catastrophic like it used to be given where the biggest braking forces are. Plus, the diagonal approach (instead of linear front and back on same side) reduces the heavy pull that would otherwise result; that thinking pre dates modern ABS as a basic safely approach--goes all the way back to the Audi C1 in the early 70's. ABS cycling can now mask/reduce some of the pulling here too. As an aside, if you ever bleed a system like this manually and watch the fluid drop carefully, you will see how it affects the front or back part of the fluid reservoir sequentially even though you ae doing the same end of the car for each two steps.
But, the downside of the set up is in the scenario that happened--it didn't just take out the less important rears, but rather it took out fully half of the braking force on the car. At least until (and if) the brakes could be pumped enough to lock up the loose rear caliper piston and then get some pressure back to the diagonally opposite front one.
All this is unfortunate, but so far as I've suggested, I would be examining the bolts and how they were installed or reused most critically. Nothing else in here is saying there is a design question, or anything fundamentally different than other modern rear disk brake set ups from many a manufacturer.
08-12-2013, 02:56 PM
#20
That sucks to hear. Glad you're ok
I just went and checked since I have rear brakes sitting in my garage waiting for me to change. The OEM pads come with new caliper bolts in both the front and rear, so I don't think it would be an issue of them using old bolts.
I just went and checked since I have rear brakes sitting in my garage waiting for me to change. The OEM pads come with new caliper bolts in both the front and rear, so I don't think it would be an issue of them using old bolts.