Is it generally accepted that one bad caliper can cause both to lock up?

[SigSaucer]

What the title says - is that possible or likely? And when I say "lock up," I mean even when parked and you pump the brakes a few times, both fronts seize up solid and you can't spin either wheel. Letting it sit over night returns to normal, only to have them seize up again when pumping the brakes. Thanks!

 

[jgue467]

I would say No. Just a coincidence both calipers need to be rebuilt in this case. Many folks don't even bother rebuilding these days, some places don't even sell rebuild kits anymore, just want you to buy a new one. Luck.

 

[SigSaucer]

Hey, thank you. What would you say if I said that both of these calipers were bought "new" 3 years ago? One is from Napa and the other is Beck-Arnley from Rockauto (don't ask lol). What about the master cylinder?

If one caliper is bad, would it really cause what I'm describing? I just find it hard to believe that one sticky caliper would cause the pedal not to depress much and lock up both front wheels instead of just the wheel with the bad caliper.

I had to really give it the beans just to drag the frozen front end back into the driveway yesterday. Even burned rubber a few times too.

 

[Bad Luck]

Hey, thank you. What would you say if I said that both of these calipers were bought "new" 3 years ago? One is from Napa and the other is Beck-Arnley from Rockauto (don't ask lol). What about the master cylinder?

If one caliper is bad, would it really cause what I'm describing? I just find it hard to believe that one sticky caliper would cause the pedal not to depress much and lock up both front wheels instead of just the wheel with the bad caliper.

I had to really give it the beans just to drag the frozen front end back into the driveway yesterday. Even burned rubber a few times too.

To answer your question, one bad front caliper locking up will not cause both front tires to lock up. It's more likely that you have a problem with both front calipers, but it could also be your master cylinder. Master cylinder is not as likely as both front calipers though.

What condition is your brake fluid?

 

[brillo_76]

I agree with Bad Luck. Most likely a master cylinder issue or an abs problem. Both front wouldn't seize at the same time..

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[brillo_76]

I would say No. Just a coincidence both calipers need to be rebuilt in this case. Many folks don't even bother rebuilding these days, some places don't even sell rebuild kits anymore, just want you to buy a new one. Luck.

Very True. However the seals to rebuild are less than $20 bucks. The pistons are stainless steal and the bleeders are not very expensive unless you buy Stainless steel speed bleeders. So it's quite expensive to rebuild them if the owner wishes too.

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[spartacus]

If thé brake lines are original they might be disintegrating creating a one way valve when you apply pressure it pushes the calipers out but does not let them release. Check the brake lines for dry rot, kinks bulges.

 

[SigSaucer]

Thanks guys. Here's more information I learned today:

Both front brakes were free again when I spun the rotors by hand today. Then I got inside and pumped the brake pedal, and both were seized solid again.

I then disconnected the vacuum line to the brake booster - no change.

I reconnected the vacuum line and then disconnected both brake lines to the master cylinder, and there was no change. Both calipers remained locked.

Now, the important part: opening the bleeder on EITHER front caliper releases both of them.

Both rubber lines look fine to me.

So, what gives?

 

[19963.4lsr5]

The rubber lines have an inner lining that delaminates and acts like a valve similar to what we have in our blood vessels.

They aren’t expensive at least. It’s interesting they both appear to be bad together.

How old are they?

Who made them if they were replaced recently?


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[JohnMc]

Pump the pedal to lock them, then crack open a line between the ABS valve body and the caliper, see if that releases it.

If so, it would indicate the 'one-way' blockage is occurring upstream of the hoses.
If not, that places the suspicion squarely on them.

But so far, you have ruled out the calipers themselves, they're not stuck.

EDIT: I missed the part about loosening the lines at the master cylinder - I think you've ruled that out as well.

At this point it's either something weird happening in the ABS valve body or the hoses?

 

[Bad Luck]

Thanks guys. Here's more information I learned today:

Both front brakes were free again when I spun the rotors by hand today. Then I got inside and pumped the brake pedal, and both were seized solid again.

I then disconnected the vacuum line to the brake booster - no change.

I reconnected the vacuum line and then disconnected both brake lines to the master cylinder, and there was no change. Both calipers remained locked.

Now, the important part: opening the bleeder on EITHER front caliper releases both of them.

Both rubber lines look fine to me.

So, what gives?

Pump up the brakes to lock the calipers again and then try loosening the fitting before the flexible brake hose. If that releases the pistons then you have a problem upstream of the flexible line and after the master cylinder. If that's the case I would suspect something went wrong with the ABS pump/valvebody.

 

[SigSaucer]

Ok, so today I pumped the pedal and got the calipers stiff again. I then loosened the fitting between the top of the rubber hose and the hard brake line (not where it attached to the caliper), one side at a time. Doing this released the caliper, though they still seem to have some drag to them.

Now check this out.....

Because of all the loosening I've been doing, I bled the fronts again. A few days ago, I could not bleed them because after a few bleeds, neither side would have any fluid pumping out when I opened the bleeder (with a helper pressing on the brake pedal, of course).

Today, both front calipers bled normally. HOWEVER, when I had my helper depress the brake pedal afterwards to test the finished system for proper operation, only the passenger side caliper is activated. The driver's side wheel now spins while the brake pedal is held down; the passenger side wheel does not spin. When the pedal is released, the passenger side now frees up and doesn't stay locked.

Trying to further bleed the driver side caliper in this situation does nothing: no fluid comes out of the caliper when the bleeder screw is opened while the brake pedal is depressed.

Hope you guys are still sticking with me because I'm not a brake guy and this is really crazy to me.

 

[JohnMc]

Seems like you've narrowed it down to the ABS valve body, that gizmo with all the brake lines on it on the passenger rear side of the engine bay. I'm guessing it's gunked up/messed up somehow?

Master cylinder ruled out: loosening lines at it did NOT free them
Calipers ruled out: loosening the bleeder did free them
Flex hoses ruled out: loosening a fitting upstream of them did free them

At this point, there's just the hard lines between the fitting at the brake line you just tried, the ABS valve body, and the hard lines between it and the master cylinder. And it's unlikely to be those lines (unless they're bent and kinked shut).

I don't think the ABS valve bodies go bad very often, you might try getting one from a junkyard and swapping it in. I think when they do go bad it's often from contaminated brake fluid. Brake fluid slowly absorbs water over time, and as it does so it slowly becomes more corrosive and it can rust things in the system.

 

[SigSaucer]

Another update.

Today I disconnected the calipers, and noticed that fluid drips out of the passenger side line at a good rate (approx. one drop per second or more), while the drip rate is much slower out of the driver side line (one drop every 10 seconds or so).

Removing the line from the top of the rubber brake hoses produces similar results.

Here's a video, not sure if this means anything: brake lines dripping - YouTube

John, thanks! I'll be replacing the ABS unit. I'll make another thread asking about that can of worms.