Replace rear drums and brake pads or not?

As mentioned in another post, just replaced front pads and rotors on my 2009 Prius.
After test driving, braking with the brake pedal was mostly fine, except for a squeak from the back as the car came to a stop.

So I cleaned the drum brakes. Then did another drive test. This time, there was no squeak, but I discovered that if I pulled the ebrake from just 5mph, the rear brakes squealed loudly (only when going forward, they didn’t squeal going in reverse). So I investigated further.

With rear up on jack stands and tires off, turning the drums by hand I discovered that both have a drag/sticky point or two across the rotation when I had the ebrake clicked in 4-5 clicks (ie there were spots of resistance as I rotated them, then easy turning). When I got to 7 clicks they were solidly locked and couldn’t rotate them, which is expected.

I sanded the pads lightly to remove any glazing, but sticking points remain when I rotate by hand. I’m guessing I have one or two ‘high’ spots in the drums themselves.

I thought the rear drums were supposed to be good for ~ 150,000 - 200,000 miles. Is this normal to have high spots in the drums at 85,000 miles (and again, it's an 2009)? And is this ok? There were no squeals during normal braking, just when engaging the ebrake. But clearly they are not perfectly round now. Or are these sticking points and ebrake squeal a solid indicator that the drums must be replaced? (I’ve seen elsewhere that replacement is a better option than machining as it’s not that much more.)

Thanks!

 

Yes, thanks Biomed01, this is the first time I’ve worked on drums (no offence taken)! Unfortunately the mechanic I used to use and trust has retired, so was attempting this myself. Was trying to avoid being taken by, as you say, a complete overhaul when all it needed was a good cleaning, as this is indeed the first pad/rotor change on the front (the rotors were excessively rusty, so went ahead and changed them too).

On my first go with cleaning the rear drums, I did not remove any parts, just used cleaner to remove the dust. But since that didn’t fix the squeal, I pulled out the star adjusters to better clean them. And yes, upon reinstall, likely didn’t set them tight enough.

As I mention in my reply to Mendel, I have read the brakes section of the manual. Is there another reference that helps with rear drum theory of operations? And I don’t have a measurement caliper, so was going from observation and testing. From what Tombuk2 commented, sounds like having some high spots is not that unusual and may not be the source of the squeal. Maybe just didn’t have stars set tight enough after cleaning?

Unfortunately, when I reinstalled the star adjusters after giving them a good cleaning, I pushed the drivers side cylinder too far over and got a little leakage into the dust boot (I discussed this here: Rear drum brake cylinder leak after push through | PriusChat).

So I’m planning to replace the cylinder next. Then reassemble and do a better job on tightening the star adjusters, do a bleed, then see how it functions.

Do you have any tips on setting the star adjuster properly?

The manual says to use the backplate hole, expand the shoe until the drum locks, then back off the adjuster 8 notches. AND, I’m having a hard time using that backplate hole, difficult to get in there and see what I’m doing.

So instead was tightening the adjuster a few clicks at a time with drum off, then putting the drum back on and seeing how much drag it has. To get the final snugging up, I’ve read elsewhere to press the ebrake 10-20 times. Is this not sufficient?

 

Thanks Mendel, I have read that manual, but I don’t have the measurement caliper. I could see some shiny spots on the drum surface, and as I mention, when I rotate by hand can feel the sticky points, so that’s how I concluded there are ‘high spots’.

 

Thanks. You mention, “The Prius likes a good drag on the rears it will finish the adjustment two minutes after you head down road.”

I thought the Prius final adjustment was done by pressing the ebrake several times to engage the self adjuster mechanism. Is that not correct? Does normal braking (also or instead) automatically adjust the star adjuster?