Need help with brakes

Based on your original description, I would have looked at the master cylinder first, but I saw you were already elbows-deep in actuator replacement before I could say anything, so I kept quiet.

You might be in luck, the Gen 1 was the last Prius to have a master cylinder rebuild parts kit available. Later models only have entire new master cylinders for sale.

Coolant, huh? That should be interesting. It's got water, which you never want in your brake fluid, so a very complete flush of the system should be in order. As I first guess, you might be lucky enough to avoid having rusted metal parts, because coolants do have corrosion inhibitors. I'd guess it's probably incompatible with the rubber parts, and they've swollen and made your master cylinder pistons and cups sticky.

If that's all that happened, maybe you can recover by just buying the master cylinder rebuild kit (yay Gen 1!), and the front caliper and rear wheel cylinder rubber kits (each kit has all the rubber to rebuild both left and right units) ... get all your lines and components very well flushed out, put clean new rubber on everything, fill it all up with clean brand new DOT3 fluid, and bleed it thoroughly.

Because of the contamination, I guess the actuator replacement was probably going to be necessary anyway. But if you happened to replace it before getting all the lines and master cylinder flushed out of contaminated fluid, there is probably some in your replacement actuator now. Maybe that won't bite you if you do get around to flushing everything promptly and thoroughly enough.

-Chap

 

There is that tradeoff. Sometimes (for things like calipers) there are non-Toyota rebuilts available for cheap ... I had a whole thread where I came to discover how vast the quality difference can be between those and Toyota's parts.

After that experience, my current feeling is when you have a genuine Toyota part and it's rebuildable, it's worth rebuilding. Then you know exactly what condition it's in. A used one, at least, probably is an original Toyota part and probably hasn't been through the clutches of a cheesy rebuilder; instead it just comes to you in whatever condition it was in when it came off the donor car. Probably ok. You could take it apart and then you'd know, about as easily as rebuilding your own.

For a small selection of parts, Toyota also offers rebuilt parts in the Toyota name, restored to Toyota specs. These cost more than 3rd-party rebuilds, but less than Toyota new. The best way I know to find out if that's available for a part you're interested in is to do some searching with -84 tacked on to the end of the part number.

By booster, do you mean the accumulator and pump? That is, the separate mechanism over closer to the right side of the car. The terminology throws people on Gen 1: the 'booster' is actually part of the master cylinder, not something you can replace separately. The accumulator pump supplies the pressurized fluid to the booster.

Interestingly, Gen 2 moved away from the hydraulic-boosted-master-cylinder design, and Gen 3 returned to it.

I don't think there's really much in the accumulator and pump. A pump, obviously, plus a check valve and a relief valve, and a pressure vessel. Maybe it'll be ok if you flush really well. Maybe it'll fail soon, or maybe it'll fail in five years.

Your decision probably won't be based on the $50 price of the part, but on the labor to change it. The A/C lines are in the way. The Toyota-sanctioned procedure is to start with a reclaim/evacuate of the A/C, open and move the lines, change the accumulator/pump, put the A/C back together, and recharge. PriusChat member rlin78 demonstrated you can do it without disturbing the A/C—if you've got ten or more hours to spend at it.

That's why if it were me, I might wait to find out if it was going to fail.

-Chap