I have owned a 2006 Toyota Sienna for about a year and half, it has 180,000+ miles on it. Periodically and totally unexpectedly, we’ll go over a bump in the road and the van will totally lock up like I have pulled the emergency break up. Which I haven’t. The van will still be in drive, the tires will come to a complete stop and we’ll have see and smell burning rubber. To get the car going again, we’ll have to put it back into park and then back into drive. Its one of the scariest things I have witness being in a car. Luckily it usually happens between 10 -20 miles per hour and we haven’t had an accident because of it. I have taken the van to 3 mechanics including a Toyota dealer and no one has been able to fix it. The only thing that has work for a time has been cleaning the speed senors, Also, it maybe worse when the A/C is on but we aren’t sure. Please help
I don’t think it’s the E-brakes locking up. I think your parking pawl is somehow becoming engaged as a result of the bumps and locking up your drivetrain. Your description of how you’re freeing the drivetrain I take as a clue.
I’m not a tranny expert. But perhaps a reputable one can get to the root of your problem.
…van will totally lock up…
Which wheels actually do this?
And is this an All Wheel Drive?
Wonder if there’s some freak wear involving the parking pawl inside the transmission and a bump in the road is knocking it into the PARK position.
You need to somehow figure out if it is the brakes or the transmission locking up. One idea is when it happens, get out of the vehicle and see if you can tell if the brake discs are hotter than normal. If they are hotter than normal, then the problem is likely the brakes. If they seem normal temperature, then it is more likely the transmission.
You’re saying you hit a bump and the rear wheels lock up but the front wheels will continue to pull the car forward?
If that is the case I think you have a broken brake shoe or some part of the park brake mechanism is broken. Has anyone removed the rear brakes to inspect?
“have to put it back into park and then back into drive”
That says it is the parking pawl in the transmission, NOT the parking brake.
Take it back to the dealer and do NOT mention the emergency brake. I suspect you are misleading the mechanics by stating the E brake is locking up when it is not.
And have it towed, do not drive it, this is too dangerous. Or drive very slow.
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Ase, if that were the case I’d think that shifting the car to P and back to D would fail to free it.
Maybe, maybe the momentary loss of forward motion and the slight “rollback” when shifting into P loosens things up. I still don’t know what is actually happening. I’d have to experience the problem firsthand before deciding what to check next.
Thank you all for your comments. It is the back wheels that stop, as soon as it starts happening I release the gas pedal so I am not sure if the front wheels are still pulling it forward or not. The last mechanic I took it to looked over the whole braking system and didn’t find any issues. I need to take it in soon and have them look at the transmission. I’ll let you all know what happens. I appreciate it
If it’s the rear wheels then the problem is not the transmission. Have your mechanic remove the rear brake pads and rotors and look at the brake shoes and drum in hat. I’ll bet you find your problem there.
I had the same problem with a Volvo V70XC. You can’t look over the brakes, in this case you have to pull the rear wheels and then pull the rotors which on the rear wheels has a small drum brake system incorporated into the rotor. The parking brake is a mechanical drum brake. Some part(s) inside the drum is broken and bouncing around and that is causing the lock up. You move the car backwards a bit and release the jam, but it will happen again. Rebuilding whole parking brake system might be required, but you have to open up both rear wheels and figure out what is going on inside those small drums.
Good point @UncleTurbo … I was assuming when the OP said the brakes were inspected, that meant there was some degree of disassembly of the rear brakes, enough to verify the parking brake system is properly lubed, all parts move freely, and generally still in working order. If that wasn’t done, I concur that is an obvious next step.
If I had this problem and suspected the parking brake but couldn’t see any reason for the parking brake to be failing, I’d be tempted to temporarily disconnect the parking brake and see if that fixed the problem. Appropriate safety precautions would be needed if this were done, since the vehicle wouldn’t have a functioning parking brake during the test.
Our mechanic figured it out, thank you all for your input. There was a misshapen cylinder in the rear wheel breaking system.