Brake issue

[Mr.Rav4]

Hi!

Brake issue. My brake pedal is normal and the brake booster works when I push the pedal, and start the car. The pedal also get harder when the car is not running, and I push the pedal several times. When I drive and normally use the breaks, it Works fine. But when I use the breaks a lot, and push the brake pedal several times, the pedal gets harder and harder, and the brake effect are nearly gone! I give the car some seconds, and the pedal and brakes is fine.

Pad, discs and amount of fluid is ok. 

Any tips?

 

Edited August 19, 2019 by FROSTYBALLS
Topic title edited to reflect subject

[IanML]

Sounds like a brake booster vacuum leak.

[Mike169]

Hi, if your car has a rubber hose pipe between the brake booster unit and the inlet manifold they become detached on the inside and close up the bore size of the hose....its cheaper to try a new hose, it has to be the correct hose, very strong. Mike.

[Mr.Rav4]

Hi!

I tried to change the rubber hose. Still same issues...  When I run with the car, and push the pedal, the brake effekt dissapear and the pedal gets harder. After 4 push the warning light for handbraks blinks, pedal is very hard and the effekt is almost gone. The brake fluid level is correct.

Tips?

 

[IanML]

According to the parts catalog, there are 3 hoses and 2 connector tubes.  The problem could also be in the brake booster (aka servo).

[roadster-rav]

Is this a petrol or diesel ( sorry but I'm not a RAV4 expert)? The brake servo relies on vacuum from the inlet manifold and for a diesel this would probably be artificially created with a butterfly valve restricting the inlet. A petrol engine already has a throttle butterfly so should work with normal manifold depression. Some diesels will use a separate vacuum pump rather than manifold depression. The pipe connecting to the servo reservoir normal has a one way valve so that the reservoir can retain some vacuum when there is no 'suck' available from the engine but this will only last for a few strokes of the pedal and that is why the pedal goes hard after the engine has stopped. An open throttle or an idle speed which is much too high will also prevent vacuum being maintained. Another cause of failure is when the flexible pipe feeding the reservoir gets old and soft it may collapse inwards and block. I have also seen unsuitable pipes incorrectly used for vacuum applications which collapse very easily.