SpecialRequest

For a '96 Civic CX, D16Y7 engine.

After bleeding the brakes due to how dirty the fluid was (it was pitch black), I started to encounter a sinking pedal when I am stopped at a light or stop sign. I mean, gradually but completely sinks to the floor at times. At first I thought there may have been air in the system still, so I went ahead and bled it again, but the same symptoms have occurred. After doing some quick research, it has been determined that it is a faulty brake master cylinder as it's most likely leaking internally.

That being said, what would be better yet more economical route to take: rebuild the brake master cylinder or replace the entire unit with a brand new one? If I can rebuild it with new seals or what not, I'd like to go that route, but I would rather seek the advice from others on here who have experience with both and can give their take on what's the best route to use.

Thanks!

Former User

The MC may be fine, and the sinking pedal is caused by air still present in the hydraulic system.

Detail how you bled the system.

SpecialRequest

RonJ,

I used the method as described in this thread using the gravity method.

Former User

^Good method.

You say gravity method but the procedure also involves pressing the brake pedal. Please clarify.

Did you bleed the wheels in the proper order?

Did you route the bleed hose UPWARD over spring and back down into waste container?

How many pedal down-up cycles did you do per wheel?

Did you also bleed the MC?

tony_2018

Gravity bleeding the brakes, uuuhh no.

jdblock

That is not how you gravity bleed brakes. Sounds like a great way to suck air into the calipers.

Gravity feed is simply opening you bleeders and letting the brake fluid "gravity feed" for a few hours.

It's actually a really good way to bleed the system but you can't let the reservoir run dry.

SpecialRequest

Sorry, I had my methods mixed up.

Now that I think about it, I may have incorrectly bled the system. The correct order is Right Rear, Left Front, Left Rear, and Right Front. I most certainly ended up doing Right Rear, Left Rear, Right Front, and Left Front.

Correct. I also made sure the hose was all the way in the fluid of the waste container so no air is sucked in.

I did 12 for each wheel, and then made sure I refilled the MC so no air seeps in.

If you're implying bench-bleeding the MC, then no I did not.

I had my terminology incorrect, my apologies.

Gravity feed consists of opening all of the bleeding valves, correct?

Former User

Not bench bleed. It is the last item discussed at the end of the post at your link. Given the soft pedal, you should also do this final step.

SpecialRequest

Got it. Looks like I'll go ahead and buy 12 feet of clear tubing and go that route then.

Former User

One additional step that I take when bleeding the wheels is to tap the caliper/wheel cylinder with a rubber mallet after the 10-12 pedal pushes. Surprisingly, the tapping often releases some bubbles that were stuck in the caliper/wheel cylinder. I then repeat the pedal pushes and tapping until the tapping no longer releases any bubbles.

SpecialRequest

Ah, excellent point!

SpecialRequest

Update:

Ended up taking it to a dealership to get it done (thank you VW Goodwill Dealership card) and even after the brake service, the pedal does exhibit the same symptoms as before.

Out of curiosity, do faulty wheel cylinders also exhibit similar symptoms as well before they fail?

tony_2018

After driving it what color is the brake fluid? Also go ahead and inspect your cylinders and calipers for any leaks. Another thing is that if your guide pins are seized up it could also cause this smooshy pedal feel as well. Alot of things to look at, suggest you get started.

SpecialRequest

Brake fluid is clear, not dirty at all. Same color as it was when I got it done last time. No fluid leaks anywhere, not even around the wheel cylinders.

I can only conclude that it is the brake master cylinder that is faulty. Besides, for a 20 year old car, I expect the car to go out anyways.

It just sucks that I got the brake service done first only to find out that the brake master cylinder was indeed faulty.

tony_2018

Check your guide pins?