OK, I've been reading the other posts about grabby brakes and no one has quite answered my problem, that I've found... About a year ago, the rear brakes became very susceptable to moisture and started grabbing. After a few stops the grabbing would subside, but I could still feel the rear brakes engaging a little earlier or more than the front brakes (the rear-end of the car would hunker down a little). So I replaced the rear shoes, the old ones had about 90K on them, not worn real bad and had plenty of life left. I made sure that when I installed them to clean everything, put a skim of silicone brake grease on a couple of the friction points and set the adjusters down so they would be able to auto adjust to the right setting. The grabbing didn't stop, so I've lived with it for a while and finally got around to replacing the front brakes on the assumption that maybe since they were old that they may not be stopping the car as much as the new rear brakes were. Didn't help, in the back of my mind I'm wondering if there is possbily something wrong with the master cylinder and the balance between front and rear brakes is off. I'm going to go clean the rear brakes again today and crank the adjusters back to see if they adjust to a better position this time around. The drum and disc surfaces are in good shape and color. Anyone ever had issues like this? Can the master cylinder get its balance messed up? BTW, I've been driving this car for 3 or 4 years, so I know how its brakes used to perform, so it isn't me not knowing how brakes feel on these cars. Any help would be greatly appreciated.
When you look at the rear brake shoes, see if they look glazed. If so then they should be replaced again. In addition I suggest that you look at the rear drum interiors and see if they look burnt or glazed. If so then the drums should at minimum be machined and ideally replaced. The maximum inside diameter is 201 mm, standard is 200 mm. If you still have a problem then I suggest that you have the brake system checked by your local Toyota dealer. There is a procedure to check the system solenoid for each wheel, within the brake pressure actuator. If your car has not lit any of the brake or ABS warning lights then no DTC has been logged and it will not be easy for the tech to find a problem.
Thanks for the info, but I looked at both sides today and the shoes are perfect, nice and dry(rough) looking and the drums still look good, didn't measure them though. The brakes haven't been dragging because my MPG has actually gotten better over the last year or so, about 50MPG during the summer. It is really like they are being actuated by the system more or sooner than they should be and is more pronounced when they are wet. As far as I can tell it feels like both sides are behaving the same hence my musings about it being a master cylinder type issue. I backed off the adjusters, so we'll see if things get better this weeks, some rain is in the forecast so should be a good test.
Check the drums for out of roundness and hard spots, as well as contamination. Might just as well take them to a shop and have them turned. Had the drums ever been serviced before this started to happen? Is it just one side or both?
Hey G, this is the first thread I have come across to describe my issue as well. I have a 2004, bought 2nd hand with 130k kms. It wasn't my primary drive, but when I did drive it I noticed the grabbing of the rear brakes. I inspected the pads/drums and all looked to be in great shape. I was wondering, given the age of this thread, if you have made any discoveries in regards to this problem. Hope to hear from you soon.
I have had no new discoveries with this, I've been living with it. I have found that if I apply the e-brake for a little bit while driving to dry out or scrub off the rust, it helps. I really need to replace the drums and see if that fixes it, they are the only brake part back there that I've not replaced.
Filing off the leading edge of the brake linings at 45 degrees will help. Also if the linings are glazed rub them over with course emery or sand paper to remove all of the glaze. (North American cars only) John (Britprius)
While I would not tell anyone not to get their brakes checked, perhaps this situation is due to rust that occurs while the vehicle is parked, and more or less normal for the first few stops. Comes down to the lack of a corrosion resistant material in the drums and rotors, as well as the less than typical usage due to regen braking. My own experience has been a general lowering of corrosion resistance in steel used everywhere but body panels (frame, fasteners, etc.). This was always a knock on foreign cars "back in the day," but now extends to domestic makes as well.
I have an 04 Prius as well, purchased used, and it has always had this weird phenomenon where it has very grabby rear brakes when it has been raining or if it is wet. Fine when it's dry. The brakes grab and pull the rear end down at low speed. I've learned to press very lightly while braking at low speed to avoid lurching. Been doing this for years now. Now, I have developed an error dash light and error codes that may indicate the 'skid control ECU' , actuators, or relays may be bad. I am thinking that this weird brake thing was probably an electronic issue all along, and not the mechanical rear brake shoe issues you guys and I have all been assuming it was. Any thoughts? I would recommend that you get an error code scanning performed at the dealer next time you're there. Please share your outcomes here. I will do the same after it is resolved. Thanks.
Well I think I've solved my problem. Over the past couple years I've replaced the shoes, the springs and the wheel cylinders. This last weekend I finally got around to replacing the drums and while I was in there I replaced the shoes as well. I also scratched off the rust on the bumps on the back plate where the shoes rub and put some sil-glyde silicone grease on all six of the bumps. It rained today and there wasn't any grabbing, mine were bad enough that they would grab most anytime. I hope this is the fix, I will update in a few weeks whether it truly fixed it or not.
ggarman, you live in Ohio where its wet and slushy. Your grabby brakes will be back once your new parts get a good layer of rust. Forgive me if i speak the obvious, joe26 touched on it, but no one talked about making friction stops to clean the brakes. Under normal braking conditions your car regens until about 3 mph then switches to brakes. This puts very little energy into your brake components. Great if you live in California, but not so perfect for those who have real weather. When its wet out and your car has been sitting your brakes can get grabby. Traffic permitting, put it in neutral and bring the car to a stop from 45 - 55 mph. This prevents the Prius from regening so it uses the brakes like any other car. A couple friction stops every so often or as needed keeps everything smooth.
The brakes worked fine up until 2011, so I'm hoping that this last bit of work will get it back to normal. If it doesn't, then I need to move forward up the lines to the other components that actuate the brakes.
Goldfinger does give some useful advise on reducing corrosion on the rear brakes. This applies even more to those with Prius in the rest of the world that have disc rear brakes. However do not take the car up to 55 mph and change into neutral as this could destroy MG1 by over speeding it. MG1 is designed with a software limit to turn at a maximum of 6500 rpm. This speed is reached at 41 mph if the ICE (internal combustion engine) is not running. John (Britprius)
Well, brakes are still fine, its been a fairly wet summer and the brakes show no signs of grabbiness. I'm considering it fixed for now!
Final update, the fix worked for over a year. I just traded in my 2005 for a 2013 and am lovin' it. Good luck to all those with the sticky brake issue, I hope my fix works for you.
This is old, but I will add that my mechanic fixes my "wet weather grabby drums" by putting some sil-glyde silicone grease on all six of the bumps on the back plate where the shoes rub (as ggarman mentioned). Been doing this once a year for 4 years. Solves my problem without doing all the other related work mentioned above.
