Over memorial day weekend I noticed some squishy brake feel. Now I notice that it brakes fine, but the last few feet feels like the brakes slip or something-it needs a bit more distance to stop. Of note:

-Brakes build and hold pressure fine with engine off, when I start the engine with my foot on the brakes it does sink maybe an inch or so -no Brake worn light/notice -I feel like I can hear the plenum move when engine is on and brake is being actuated, is this a bad brake booster? -brake fluid level has not notably decreased -car has ~167000 miles on it -have not recently had any brake work done before this issue -no shuddering/pulling even when applying brakes hard -occasionally I can hear a whistle when engine is at idle and I press the brakes. Only occasionally and I cannot replicate it on demand.

My culprits that my research seem to point me towards are: -master cylinder -brake booster -swollen brake lines?

My question, anyone aware of a way to eliminate any of those options as a possibility? I hate to go throwing random parts at it in hopes of a repair. Thanks!

 

The flexible brake hoses are rubber. They need to (= should) be changed every X years, I think it was 6 years or 156k km (102k miles roughly) whichever comes first. If you suspect them, remove a wheel one at a time and have someone inspect the hoses from the brake pipe all the way to the caliper visually while you’re pressing down the pedal.

The brake fluid should be changed (recommendation) every 2 or 3 years.

Squishy brake pedal can be many things but perhaps start with bleeding the brakes properly to see whether you have air in there somewhere. It is another question where the air would originate from.

 

I know nothing of your vehicle or your location in the world.
It is normal for the brake boost to “charge up”. Its after affects that would worry me.
You mention “not notably decreased”. What does this mean? It should not decrease at all.
As ​​​@kajtzu suggests, many overlook the importance of brake system maintenance.
Cheers

 

I absolutely forgot all about those brake hoses, I'll dig in and check those next and likely change fluids while I'm at it, seems foolish to open the system up to change a part and skimp on new fluids.

The pedal does not really move once I start the vehicle if I have my foot on the brake pedal while starting it. I think this was one of the ways I've read to see if I can rule out the booster failing or not. As for not notably decreased, I mean that I did not take a caliper reading on the fluid level, but as far as my untrained eye can see the level is where it has been for some time. I will say that I am likely very guilty of overlooking brake maintenance on some aspect, as I was more worried about the bigger repairs first. Now it's all a game of catch-up for me. Thanks for the replies gents, I've got some new leads to dig around on and hopefully find the problem.

 

So I went through and checked for any leaks along the flexible brake lines, none to see.

https://imgur.com/a/GzZfgo0

I did notice that the line going into the booster has some wiggle with minimal effort. Does this seem normal to you guys? I'm kind of leaning towards something on the vacuum side since the fluid level has stayed the same with no signs of fluid leakage. I tried to trace the vacuum line to look for any obvious holes or leaks but couldn't see/ hear anything. Any recommendations to do a better job at detecting a vacuum leak?

 

smoke test !
Also, the rear brake lines are known to rust.