Master cylinder clunk on brake press

[FunRunner]

2020 LTD, noticing a clunk from the master cylinder when pressing the brake. It clunks about 1/4 down the first time, 3/4 the second time, and nothing the third time, before starting over. There is a small give in the pedal, but it is not at the linkage itself. Has anyone seen this before? I'm unsure if it's a booster or master issue

 

[xandercaged]

Theres a pump at the cylinder's base, connected to the master brake's passenger side. Its initial effort moves the cylinder that causes a knock against nearby metal. You stop the noise by stuffing rubber in the gap.

 

[Tecla.S]

2020 LTD, noticing a clunk from the master cylinder when pressing the brake. It clunks about 1/4 down the first time, 3/4 the second time, and nothing the third time, before starting over. There is a small give in the pedal, but it is not at the linkage itself. Has anyone seen this before? I'm unsure if it's a booster or master issue

no, it's not "just how it is.", it's either a failing master cylinder or the booster doing something stupid, possibly internal valve slop. the "give" you mentioned? its the system bleeding pressure somewhere it shouldn't., pull vacuum on the booster, pinch off lines, and see what changes if not youre probably halfway to break failure

 

[playthings]

no, it's not "just how it is.", it's either a failing master cylinder or the booster doing something stupid, possibly internal valve slop. the "give" you mentioned? its the system bleeding pressure somewhere it shouldn't., pull vacuum on the booster, pinch off lines, and see what changes if not youre probably halfway to break failure

This is what you need to do exactly, OP. Don't dismiss it. This thing happened to me and it turns out I need to change a lot of parts lol.