Intermitent Brake release?

Good day Prisu Chat folks.

My vehicle:
2005 with 135,000 miles

I encountered a situation 2 days ago (1/8/2013) that makes me believe something may need to be tested.

While sitting at a stoplight on an uphill incline, there was suddenly a rather pronounced "rattle" and immediate release of pressure on my brake peddle. The vehicle began to roll backwards and i could not stop this no matter how hard i stood on the brake.

I used the parking brake to hold the car, turned the car off and turned it back on.

Since then i have not been able to reproduce the symptom, but my mind is making me think the brake "feels" different than it used to, maybe slightly spongy.

I have read about brake actuators on this forum and believe I may have encountered an intermittent fault there of.

Any suggestions on what I should test to determine the cause of my issue?

Thanks!!
Mark

 

PriusGuy32,
I checked the 12v on Monday out of pure bordom. W/ the car in "on" not not "ready" it shows 11.9v, and in the "ready" sate shows 14.0 ~ 14.2.

The 11.9 held for about 15 minutes w/o dropping, and was done pretty much right after a 20 minute commute. so it's a tad low but not draining off. Could that cause random issues?

I have metered many car batteries, and load tested them in the past. Most sit between 12.3v and 11.8v and as long as they don't drain down their fine. and the one in the car doesn't drain down. However, this car isn't "most" cars either.. Are the implications of a 11.9v hold different for this car?

Thanks!
Mark

 

John Hatchett,

I am the 2nd owner of this car. Picked it up in Jan 2010 with 98,000 miles on it for $6,000 cash. I own 3 vehicles, all have over 130,000 miles on them currently . Firm beliver "One man's trash is another man's treasure" ha-ha. (2001 isuzu rodeo 175,000mi, 2003 honda cr-v 143,000mi, 2005 Prius 130,000+mi.)

The dealership installed a new 12v battery at that time, as well as performed the coolent pump replacement recall. They also put a set of Goodyear tires on it that formed blisters in the first year (dislike goodyear, replaced all 4 with Michelins).

Really though, all I have done to it is oil changes and transmission fluid changes. Oh, had a trunk leak where water was weeping behind the tail light into the 12b battery compartment. (that's when i found out the car had been rear-ended at one point, ver minor, but enough to bend the sheet metal near the tail light). Fixed that mess and never looked back.

Would Autozone be able to test the Brake Acuator from their scan tool? I'm not getting any "check" lights on the dash.. Which makes me doubt it threw a code :-(

 

John Hatchett,

Would you reccommend I pull the battery out and do a good load test on it?

I haven't seen any weird mileage drop, although during this past summer i did notice about once a week the HV battery was down to 2 bars after sitting in a parking lot for 4 hours at 100+ degree temps.. figured it was just running the cooling fan for some reason..

 

John Hatchett,

I'll toss the charger on it tonight (have a trickle on the Isuzu i can move over to the prius).

My main concern is.. will this occurr when I Really need the brakes to work.. But it seemed to be only related to the hydrolic system, not the regenerative system.. so could this cause an accident.. not likely since the hydrolic system kicks in under "extreme circumstances" or "under 7mph"..

Though it does make me hesitant to put my 13 month old daughter in the car..

 

John Hatchett,

I think I will air on the side of caution and have it checked out as you suggest.

I am picky with the shops I let touch my cars. I called Hancock Automotive (their shop looks like a showroom! and they have worked on my other 2 cars in the past years) They have a new ASE Master Toyota Tech they hired last month. They put him on the phone with me and I was able to describe the situation to him.

Scheduled an apointment for tomorrow.

 

All right.

Shop says, "Traction battery is at 68% available capacity. 12v Battery is shot."

Replacing 12v Battery tonight. Still not sure if the 12v is bad.. they said it discharged to 7v after "several minutes of testing" which to me says they discharged it without knowing its not a regular 12v Car Battery..

Oh well.

New front tires, passed state inspection, and a new 12v battery. We'll see how it goes.