Is my brake actuator failing?

Front rotors are extremely hot? How do you know this?

 

welcome!
i would tackle the mpg problem first. have you done any maintenance since purchasing? tires pressure/oil level/air and cabin filters/fluid top up

can you post a recording of the clicking after you have 5 posts? most describe the brake sound as buzzing, which is the fluid pump pressurizing the system

sounds like a great car, all the best!

 

There are various ways to find out. If they have been dragging heavily, touching them by mistake can be very convincing. Other options include walking past the front of the car and feeling the radiant heat through your trouser legs, or watching the air shimmer as you look past the front wheels.

I once had a truck show all those signs after coming home from a simple dealer visit. I did not touch the rotors with my hand, because the air shimmer and the heat on my legs persuaded me out of it.

When I took it back to the dealer, the service writer fed me a line about "oh yeah, they do get hot" and pretended it was normal, so I just found their mistake myself and didn't use them for any more brake work.

If a Prius is making rotors extremely hot, that will certainly explain an MPG drop. If you follow a simple little test-drive protocol you should be able to feel stone-cold rotors on a healthy Prius at the end. The key to the protocol is to avoid any use of the brakes during the drive, including the stop at the end, otherwise they will inevitably be a little warm. Extremely hot indicates a problem.

The problem could be something simple at the calipers themselves; always worth checking before fretting over worse possibilities. If it's been that way for a while, the calipers probably need attention now anyway, even if the root cause was elsewhere.

 

Congratulations on buying my dream car... 2009 Prius was the last great year for this car... Super reliable, super easy to maintain... Once you get this brake problem resolved you're gonna love it.

And ironically, many Prius newbies who buy used are often sold new rotors and pads by mechanics who think the fact that the rotors aren't clean shiny is a problem, when the reality is in some driving scenarios the regenerative brakes work so well that the mechanical brakes just don't get used very often.

 

I was asking so the OP would answer. The low MPG and overheated rotors seemed odd. Just wanted to know how he quantified the hot rotors.

 

do you know how to check your oil level?

 

a first degree burn from touching a recently used rotor is normal... A hot metal smell and second or third degree burn, or instinctively pulling your finger away before you get close enough to touch it is when there's a problem...

As for your low MPG that's within range of normal, especially if you have cheap or underinflated tires, have yet to optimize for max MPG...

 

I think the OP should not worry about the brake actuator right now since no skid control ECU warning lights are on. Rather, it would be better to investigate the front disc brakes to see why they seem to be running unusually hot.

Always disconnect the 12V battery first, before doing any work on the brake system. Depress the brake pedal a few times after doing so to use up any stored charge in the brake capacitor bank which provides emergency 12V power.

Then raise up the front of the car and try to spin the tires. As you spin one tire, the other tire will rotate in the opposite direction since the gear selector is in P. Some effort will be required since you are rotating both tires and the differential within the transaxle. However if this take unusual effort then the brake pads may be dragging.

If you decide the pads are dragging, then remove the tires. Inspect the thickness of the outer and inner pads. If the inner pad has worn more than the outer, that may be evidence of dragging. Look for discoloration on the rotor which also would be evidence of a pad dragging.

Lubricate the slide pins that allow the caliper to move as the piston is actuated via hydraulic pressure, to avoid this problem in the future. Use lithium soap base glycol grease intended for this purpose.

The pad thickness when new is 11 mm and the minimum spec is 1 mm. If you see that the inner pad has worn much more than the outer, it might be good to replace the pads now. Always replace the four pads on both sides of the axle, if any pad is bad.

There are many posts about how to perform the front brake pad work in detail. Also reference the factory repair manual info at techinfo.toyota.com