General brake question (honda)

[Jaguar_5]

So I have a friend with a older integra, he was having some problems with his brakes, he took it somewhere for a free brake inspection, and they said nothing was wrong so after I talked to him I had him bring it over

Air was definitely in the lines, there was lots of nasty red brown gross brake fluid, I did a full flush and bleed on all 4 calipers, replaced the fluid in the entire system. His brakes felt great after this, infact he thought the problem was fixed for about 3 weeks, but they're getting spongy again, I didn't find any leaks, and he's been looking for any drips where he parks but nothing.

So I'm pretty sure it must be a seal in the master cylinder, or brake booster? Probably the master cylinder, right? How do I diagnose this before we start throwing parts at it?

 

[Poodles]

master, or look for a bad cap on the master.

if air (with moisture) is able to get into the system, the moisture gets into the fluid and eats the lines from the inside out...

 

[Ckanderson]

master,...

.

 

[AF1JZ]

I'd say it is the master cylinder. I had a civic one time and when you would be at a stop light, the pedal would just go to the floor. Then the car would pretty much lose brake pressure. So, I replace that and bled it real good and it was fine after that.

 

[Jaguar_5]

Alright, nice to see that you guys agree with what I was thinking, so I'll have him replace the master cylinder

AF1JZ, that sounds like exactly what he was explaining before he brought it to me!

Thanks guys, I now have alot more confidence that the master cylinder is the culprit

 

[Ckanderson]

if he needs a master cylinder let me know....

even with shipping I can kill auto parts places!

 

[ilikebigbutts]

is the peadal getting spongy while driving or all the time?brake fluid is hydroscoping and even if it gets the slightest amount of water in it (1-3%) its boiling point drops like 150 degrees

 

[suprarx7nut]

I had a 91 accord with the same problem. Though i didn't leak any noticable fluid. There was a very small, nearly invisible gleaming trail of brake fluid going down the firewall inside the car.

Replaced it and it was fixed for good.