Could driving with a parking brake on wear out the normal brakes?

October 19, 2007 7:29 PM

Could driving with the parking brake on rapidly wear out or destroy the brakes on a car?

The car in question is a Ford Taurus (fourth generation, not sure of the exact year). It was driven for several minutes (not more than half an hour) with the parking brake engaged, and towards the end of the drive lost almost all breaking power, which meant it nearly failed to stop in time to avoid hitting the car in front of it.

What damage could have been done by driving with the parking brake on? Are the two things related? How much could this cost? Help!

posted by Dasein to travel & transportation (20 answers total)

I should have added - this is a fourth generation Taurus, in case it matters.
posted by Dasein at 7:30 PM on October 19, 2007

You probably need new brake pads: go get them.
posted by unSane at 7:31 PM on October 19, 2007

Previously.
posted by cerebus19 at 7:31 PM on October 19, 2007

In full disclosure, I know hardly anything about cars - BUT, I do know that I have driven with my parking brake on at least five to six dozen times, with no notice in the change of my actual brake-brakes. 2002 Toyota Corolla driver here.
posted by banannafish at 7:32 PM on October 19, 2007

Parking brakes are generally a secondary activation system for the same actual braking mechanism as the main brakes, so yes, driving with the parking brake on will wear out your brakes.

What probably happened to you is brake fade due to the heating that driving with the brakes on caused in the braking mechanism. Letting the brakes cool down should restore some of your braking power. But you've put the equivalent of many months' wear on your brake pads, and you should get them checked and probably changed ASAP.
posted by flabdablet at 7:34 PM on October 19, 2007

Driving with parking brake on = worn pads = $60(they come in sets)/tops (+1-2 hr install).

$250 at a stealership, more like $120 at a reputable garage (replacing brakes is cakework).

Or DIY. Brakes were my first DIY.
posted by SirStan at 7:39 PM on October 19, 2007

Thanks for the advice so far. I'll try the push-test that's recommended in the thread than cerebus19 links to, and I will take the car into a garage tomorrow. Sounds like the brake pads will probably need to be replaced (though maybe they're just overheated - here's hoping). Thanks to unsane, flabdablet and SirStan. Any more advice is welcome.
posted by Dasein at 7:46 PM on October 19, 2007

there is no way we can know what is wrong with your car over the internet. take it to a mechanic and explain what happened. don't mess around with your brakes!

that said, almost all parking brakes work by engaging the rear brake in some way. the rear brakes on a taurus are either disc brakes or drums, depending on your model. normally driving around with the brakes on won't destroy your brakes but what i suspect happened is:

with the e-brake engaged, driving around made one or both of the rear brake assemblies get very hot. that heat caused the fluid in your brake lines to boil, and now you have bubbles in your rear brake lines. these bubbles are compressible, as opposed to the brake fluid which is mainly incompressible. therefore as the bubbles grew, the braking effort required increased, until the end of the drive.

good news is that you probably only have to bleed the lines. a shop should be able to do this in like 20 minutes. even if the rear brakes are totally shredded, most stopping power comes from the front brakes anyway.

i cant imagine that a few minutes only of driving would totally wear your pads/shoes down. and you probably have drums on the back, as discs that got that hot would seriously warp the rotor, and you'd feel a big vibration every time you hit the brakes. new drums should cost something on the order of $300 - $500 if worse comes to worst.

of course, there COULD be worse problems, which is why you should have a shop lift it and check it out to be sure.
posted by sergeant sandwich at 7:47 PM on October 19, 2007

Thanks for that answer, sergeant sandwich. I will definitely take it into the garage tomorrow. I'll ask about the possibility of the brake fluid needing to be drained. And for the thread, I think the rear brakes on the car are drums, not discs.
posted by Dasein at 7:51 PM on October 19, 2007

May I suggest that before you take tell the mechanic your tale of woe that you simply ask him to replace the brake pads and bleed the lines. Brake shoes are easy, quick, and cheap -- drum much less so. If he thinks YOU think they need replacing, well, by golly, looks like they need replacing. If however, they actually DO need replacing, he's gonna come get you and show you the damage to justify the replacement.

Unless you are one of the six people on the planet who knows an honest mechanic.

[NOT MECHANICKIST....ok, maybe a little bit]
posted by BitterOldPunk at 8:26 PM on October 19, 2007 [1 favorite]

Exact same thing happen to me my grandpa and mechanic both said that it probably just got the brake pads hot and therefore temporarily lost some braking power. Everything wad fine the next day.
posted by DJWeezy at 9:12 PM on October 19, 2007

Take it easy. That sort of brake application won't wear out anything that wasn't nearly there anyway.

The reason teh brakes failed to operate at the end of teh journey was that the pads/shoes (depending on what is on the car, I'm guessing pads) were overheated on teh surface.

The most likely fix is to brake normally for a hundred miles or so. The face of the rear pads will have glazed and so be 'cooked' and not brake so well. If you just break normally and wear away this 'cooked section' your braking will return to normal. It is extremely unlikely that you caused an issue in the brake fluid, unless the fluid is very old - the age of the car suggests that this is unlikely.

However - after driving the car for a while and braking in a normal manner - does the pedal feel very spongy or bouncy? Is this getting better or worse?

If your pedal comes back in terms of feel, you have just reduced your rear brake pad life, and that is the only issue. If it stays spongy, then you MAY have caused a fluid issue, but it is more likely that you have damaged the pad material through excessive heat. Change the rear pads (if that is actually where the parking brake acts) and see if the pedal comes back before getting involved in the braking hydraulics - that could be expensive.
posted by Brockles at 9:43 PM on October 19, 2007

When I was in driver's ed during the summer that I was 16, my driving instructor had me drive a late-model Taurus to the dealership to get some routine service done. We were sort of in the middle of nowhere, so this involved a 45 minute drive or so through country roads.

About five minutes from the dealership, I noticed, in horror, that the parking brake had been on the entire time.

As quietly as I could, I turned it off. The instructor had the same horrified look. I thought I'd failed. He said: "Look, I'm so sorry, I honestly would have told you within a few minutes if I'd seen you do that. Let's just get this car into the dealership and get her some new brake pads."

We did. Apparently, "she" needed the brake pads at that point, too. Oooops.

By the way, I still got an A.
posted by InnocentBystander at 10:21 PM on October 19, 2007

Thanks for the continued advice. BitterOldPunk, I don't necessarily know an honest mechanic, but I will take the car to a CAA-recommended mechanic, which is the best I can do.

Brockles, I appreciate the advice to keep driving and wear off the cooked portion, but complicating all this is that it's not actually my car (nor was I the driver), and it needs to be returned to its owner soon, so I have to get this sorted out ASAP, and if that means spending a little money, so be it.
posted by Dasein at 11:15 PM on October 19, 2007

If you boiled the brake fluid, you should have the whole system refilled, not just bled. The brake fluid's heat characteristics change (and not in a good way) after it is boiled.
posted by knave at 11:21 PM on October 19, 2007

You guys are freaking me out. I accidently drive with the parking brake on all the time and my brakes work fine. They were just inspected and there wasn't a problem. Am I just freakishly lucky or is the danger to the brake pads overstated?
posted by Justinian at 11:54 PM on October 19, 2007

Justinian, you haven't ruined them if your brakes continue to work normally. Every time you do it, you're taking a little life off your rear brake pads, that's all. (Parking brake generally activates only the rear brakes.)
posted by knave at 2:25 AM on October 20, 2007

A while back, maybe last winter, I heard a question about this on Car Talk. The two brothers got into a hilarious argument because one thought that driving with the parking break on could cause some (but not a ton of) damage, and the other thought that if you could drive with it on, especially without noticing, it couldn't really hurt anything.
posted by lampoil at 5:31 AM on October 20, 2007

I rent a lot of cars, but I don't always know everything about them. So a lot of times, I drive for like ten miles with the emergency brake on. That doesn't say a lot for me, but it really doesn't say a lot for the emergency brake. It's really not an emergency brake, it's an emergency "make the car smell funny" lever.--The late, great Mitch Hedberg
posted by Deathalicious at 5:40 AM on October 20, 2007

You guys are freaking me out. I accidently drive with the parking brake on all the time and my brakes work fine. They were just inspected and there wasn't a problem. Am I just freakishly lucky or is the danger to the brake pads overstated?

The fact that the brakes didn't work at the end of the journey suggests the pads were overheated. If you don't overheat the pads, you just put a small percentage of extra wear on them.

There is no need at all to panic if you do this.

It is incredibly unlikely that doing this will boil your brake fluid. If the praking brake was on enough to generate enough heat to do that, then you'd very much notice that the car was behaving very oddly - hardly moving and needing full throttle to move it and the like. Putting a little heat in for a long period will cause the pads to 'fade' (surface overheating of the pad material). You need to put a huge amount of heat into the system in a short time to boil fluid.

Modern cars have very, very good brake fluid. Boiling fluid is mostly a thing of the past/extreme cases. I don't think it would be possible to drive 10 miles in an 'extreme case' without noticing, so chances are the brake wasn't on all that hard.
posted by Brockles at 8:32 AM on October 20, 2007