Brakes failing randomly

[Fraser434]

When I was a mechanic anytime someone said the brake pedal went to the floor = installing a new master cylinder, whether needs one or not. Check for corroded/leaking brake lines/calipers/wheel cylinders. Make sure the new master cylinder is bench bleed, and the lines are properly bleed after installation.

Checking the brake booster is easy, pump the pedal and turn on the engine. The pedal should get firm, then release pressure with engine on.

 

[Avery4]

Originally Posted by WyrTwister
For the master cylinder , first look for leaks . If it feels " spongy " , it is bad . Other than that , not sure .

Brake booster , listen for leaks . Disconnect & plug the vacuum hose . Any difference in the way the brakes work / perform .

I am with you , with the miles on the vehicle , I would replace both , if in doubt . Check out rockauto.com . Other than OEM , I do not know which brand to avoid vs. purchase .

Best of luck to you .

Thank you so much! The brake pedal actually feels great right now, very responsive and no spongy feel. It always feels great until it suddenly doesn't at random with no warning. No fluid leaks. If I disconnect the brake booster the pedal gets hard and unresponsive and I need to use a lot of force to stop as I would expect, not sure if the brakes would still randomly fail without the booster connected.

I'm thinking I will go with an OEM master cylinder if I can get one online for a decent price (and it looks like I can) since that is a critical part and could cause a total loss of braking If it fails, but for the booster I am thinking I will go with a quality aftermarket unit since it's not as critical as I can still drive with no power brakes if I have to, but I obviously don't want to!

 

[mk378]

When vacuum is disconnected is it the same as when it is connected and failed?

 

[Avery4]

Originally Posted by mk378
When vacuum is disconnected is it the same as when it is connected and failed?

It happened so quickly and I panicked so I don't remember for sure, but I think the pedal wasn't as hard as with no vacuum assist but I don't think it slowed the car down at all, not sure if it would have if I pressed it a lot harder. If/when it happens again I may be able to provide more info. I hate intermittent problems like this!