Hissing sound coming from brake pedal; brake pump suddenly cycling much more.

You have a leak—probably an internal one, that is, no brake fluid leaving the car, only leaking past a valve that doesn't seat properly anymore, and returning to the reservoir as it normally would when you release the brake.

Because of the leak, the target brake pressure isn't being held. The ECU sees when the pressure drops below target, and opens valves to send additional pressurized fluid in to bring the pressure back up. This is the gallop you feel when braking to a stop; the braking pressure isn't constant. With the continuing loss of [edit: brake fluid] back to the reservoir and the need to make up the pressure, the pump must repeatedly run to return fluid from the reservoir into the pressure accumulator.

 

If you can't deal with any of this yourself you're looking at around $1,400 in parts and another 1,000 or so in labor easily Make sure your car is worth that not that you could sell it for any of that but it's worth it to you because these cars have a bunch of other problems that are going to rear their ugly head in just a few minutes you're at the perfect mileage so there's always that so you have five or $6,000 that you could spend on this car and it wouldn't bother you basically is where you're at in a nutshell to me there's no generation 3 that would be worth that in my world at all not even a 2013 or 14 persona and very nice condition red color no damage to the seats door panels and all of that I still wouldn't do it many do and you can read all their stories most of them right here It's a very big crapshoot If you like to gamble in Vegas you may take the challenge possibly I personally wouldn't do anything I would get out of that system as quickly as I could at this point before things get really silly and they are right around the corner read on throughout these posts you see here in the generation 3 section you have a month of reading easily.

 

Pretty sure you mean brake fluid.

 

You're psychic, man. Fixed.

 

Even the best writers can occasionally benefit from an editor.

<--- coffee maker thataway shop fluids thataway --->

Teamwork!

 

Because the loss of pressure varies the braking you can feel, and the system is able to squirt more high-pressure fluid to keep raising it again, the internal leak is almost certainly inside the actuator (a/k/a booster, master cylinder, upper thing here), so you replace that:



The pump (lower thing there) seems to be working and keeping up with what is asked of it. You can probably keep that. A Toyota warranty repair would change both for good measure, which you might also do if cost is no object.