Sudden Self-Braking/Wheel lock and Skidding

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Old 05-31-14, 08:28 PM
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Sudden Self-Braking/Wheel lock and Skidding

I got a phone call from girlfriend stopped on the side of the highway. She told me she was cruising along in the left lane (at approximately 50-60 mph) when suddenly, without her taking any action, something happened as though the brakes were applied...hard. The wheel(s) locked up, and she skidded to the side of the road. She reports there was no ABS pulsing.

When I arrived on the scene, sure enough, there was a nice, long, rubber trail I'd estimate at about 3-4 truck lengths long: only one skid mark, appearing to me, as though from the driver's side front.

A quick visual inspection revealed nothing. I started the truck, at first, slowly, gently rolling it forward, then back. There seemed to be no binding or resistance so I pulled it away from traffic, farther into the median, performed further inspection but still found nothing.

The Vehicle is a 2004 Toyota Tacoma SR5, 5 speed w 4whd
(For any of you that may work at parts stores, it's red. )

The front brakes are in excellent condition. Just last summer, I replaced not only the pads but also installed new calipers and rotors. I cannot say to what degree the rear brakes are functioning other than that, due to rusty cable and hardware, as emergency/parking brakes, not at all.

Most brake problems that I'm aware of usually involve "not working when applied" not "working when not applied". I've done a bit of research with little success; especially since search terms one would use (sudden braking, "wheel lock", etc) more often apply to different, unrelated issues.

Though it involved braking, I can't think of anything (for example, an ABS malfunction) in the braking system that could cause this type of behavior. (...but others here know a lot more than I, which is the reason for this post.)

In one of the (very, very) few results I was able to turn up regarding anything remotely similar, it was suggested that the problem was more likely with the transmission than the brakes-- but even then, it involved an automatic transmission.

The best explanation(s) I can imagine is that a front end, brake (or other) part came loose, slipped into the wheel assembly and locked it up or that the same result was caused by some road debris that got kicked up. (She reports not noticing, seeing, hearing anything beforehand; just a sudden skid.)

Where the truck first came to rest, I did find a hefty bolt of some type right near the driver's side front wheel. (see photo) It may or may not be related. It's AMAZING how much crap there is littering the side of the road that we just drive past not seeing!!

I looked into as many possible causes as I could think of and found nothing. I needed to get it out of the highway, it seemed drivable, I drove it off, it seemed normal so I drove it elsewhere to look into further and ultimately brought it home, all together driving it about thirty or so miles.

Everything seems to be normal, however, she's now terrified to drive the truck again until it's "fixed" and, of course, I'm finding it difficult to "fix" what I haven't experienced, can't see or reproduce, and don't even have a guess at.

To anyone who might think I'm onto something with my hunch (about an object slipping off or being kicked up, locking up the wheel then freeing itself) is correct, (assuming it was the front wheel) where could it go that would cause that sort of reaction? I plan to pull off the wheel tomorrow to look around more closely. Any suggestions regarding specifics to check out?

If that's not it, I don't even have any other "straws" at which to "clutch". I welcome any other thoughts, ideas or suggestions regarding what could have caused this.

Can anyone identify the part I found (in the attached photo)?

Thank you for any help.
 
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Old 05-31-14, 08:38 PM
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These bolts reside in the spring brake pod of air brakes on big trucks. They are used to compress the spring brake for service or to release the parking brake in case of air failure.
Every b18 wheeler has at least four of these bolts in its spring brake pods. (parking brake)

RR
 
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Old 06-01-14, 12:15 PM
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Well, thanks, I say, thank you for that speedy response, RR.

It seem I now have, literally, no clue.

Spring Break I usually associate more with screws than bolts!
Anyway, if you can use this spring brake bolt, it's all yours!

Thanks
 
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Old 06-12-14, 02:02 PM
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If you haven't found the problem yet, I think it could be the master cylinder. I had the same kind of thing happen to me on my '84 Ford Bronco. I'd be cruising along, when all of a sudden the brakes would come on by themselves. I think the diaphragm sprung a leak and somehow the vacuum or pressure went to the opposite side and caused the brakes to actuate. Any way, after I replaced the master cylinder, I didn't have the problem anymore.
 
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Old 06-13-14, 07:57 AM
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Are you talking about the master cylinder or brake booster?
 
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Old 06-13-14, 08:36 AM
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I had an '02 Oldsmobile that did that twice during my time with it. Never could figure out a reason. It didn't make sense that brakes could be applied without an input force (my foot). Well I just found out these cars have a traction control system in them that CAN apply the brakes. From the master cylinder the brake lines go into this aluminum manifold block which is part of the ABS system but it also has a tiny hydraulic pump that can pressurize the system without your help.

Frankly this is one of the stupidest ideas I've ever heard of and ranks right up there with ignition switches that don't actually turn off the power, or brake lights activated by a computer instead of a simple switch. Crap happens and basic safety systems should not get so complicated that they CAUSE problems.

Maybe that Toyota has this kind of active control system?
 
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Old 06-13-14, 08:38 AM
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Sorry, that's what I meant, vacuum booster. Forgot to separate them.
 
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Old 07-22-14, 09:55 PM
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MrPop,
So it was the vacuum booster that you replaced; not the master cylinder?

Interesting thought regarding a traction control. Seems it's a confusing issue whether no, all or some 2004 Tacomas actually have traction control. I will look into this but don't have access to the truck right now.


In the meantime, this (lock up/skidding) has not reoccurred since.
However, just after this, a new problem manifested itself in the form of a power steering leak.
This may be reaching, offhand, I can't think of how and I never would have thought this otherwise but, is it possible there could be a connection? particularly if she ran very (very) low on power steering fluid the first time..before it was noticed?

Again, personally, I don't really see a connection but it did happen about the same time which would be a heck of a coincidence and I still haven't found any other explanations so ...thoughts?

Thanks
 
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Old 07-23-14, 05:05 AM
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A power steering leak wouldn't be related to the braking issue. Occasionally multiple things go out at the same time although it's more likely one wasn't noticed until it was brought to your attention that there were mechanical issues.
 
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Old 07-23-14, 07:21 AM
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Just more food for thought--I'm not a mechanic and I'm only speaking from personal experience but I once had a Chevy Astro van that did in fact use the power steering pump as the pressure booster for the braking system. Pretty sure it was done that way to save the space normally taken by the vacuum booster, but maybe the idea is finding its way into other vehicles? So a system connection is possible however I can't think of a reason such a system would apply the brakes in response to low fluid--at least my Astro had a master cylinder that required foot force to initiate braking.
I hope someone with Tacoma knowledge will chime in at some point...
 
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