Good Morning,

I have this strange issue. When I start up the car and put in reverse the brake feels spongy and takes time to stop the car. After few presses on the brake puddle the issue goes away and won't happen again until the next cold start.

Is my brake master cylinder going bad? if so why only on cold start?

I checked the fluid and its full and clean.

Thank

 

Could be that the brakes are ceramic, so their cold bite isn't good and once it warms up, it bites much better. That's how the Akebono ASP pads are on my TSX and 4Runner. When the warms are warmed up, they bit really good and stop better.

 

Engine vaccum is high on cold start. You're getting more assist...so the pedal will drop further more easily.

Pads don't work as well when they're cold. So even though you're getting more assist...they're making less friction.

Any car with assisted brakes will have a pedal that presses more easily if there is more vaccum in the manifold.

 

The thing is my brake pads are not newly installed and I never had this issue before. At random cold start the brake peddle is hard to press and it seems like the peddle won't even go down and the car won't stop. I wonder if the MC is going or brake booster is going bad.

 

a failing master cylinder will allow the pedal to go ALL the way to the floor.
which isnt happening in your case.

in my service manual, it gives testing procedure to test for failing brake booster. let me see if i can dig it up for you.

you might have air in your lines, thus the spongy feel. have you checked brake fluid level?

 

Brake fluid is up to the correct level. The pedal is not spongy but I'm going to bleed the lines just to rule out all of this but it doesn't happen all the time just once in a while specially if its really cold outside.

Thanks again .