Help - Need Input on what I believe is a Pooched Master Cylinder

[northguest47]

I just did a search on this sub-forum and read the one thread that has a lot of troubleshooting info in it.

Here is my situation: ('06 manual no abs)

About a year ago the brakes were bled, fluid topped up etc. Since then the brake pedal has been engaging lower and lower in the travel, very very slowly but noticeable. I have been aware of it, figured perhaps there was an air bubble in the system but the brakes were always fine so kept putting off bleeding them again. Until...

Last week I did a road trip and the pedal at this point was really low engaging, I was cursing myself for not putting priority on this. So I say to myself, no biggie, I'll get this road trip done and then bleed the system. Last sunday morning after starting up the car in cold weather and driving downhill to a t-intersection there was no brakes. Zero. The pedal went all the way to the floor. Thank God and luck I figure. I reacted perfectly, blew the stop sign, under-steer slid the corner and didn't ditch the car, roll it, or worse off get tee boned by a car heading across (no stop sign the other way). 'Nuff said we all know hindsight is 20/20 and this was my fault.

One last thing to note is that as this pedal fade was happening I always noticed that if I pumped the pedal once or twice, the brakes would engage 'a little higher in the pedal', but then after driving it would go down to the usual spot. Remember this pedal fade happened very slowly and predictably, and also sped up a bit over the last 8 weeks I'd say.

So we did some testing and the thing is the brake fluid is at the exact same level and its clean. I haven't taken off the tires yet - had to borrow my buddys car complete the road trip. We were thinking its the master cylinder as in since no fluid appears to have leaked this is an 'internal' hydraulic failure. On ice with the car rolling putting the pedal to the floor won't lock the rears but one of the front tires locks, so its still barely working.

What do you think? I have ordered and picked up the master cylinder, work to be done next week so please if you have any input let me know if you read this this weekend, or next week.

Should we try to bleed first in case for some reason it could just be an air bubble? Or do you also think its likely the master cylinder? I can return it if its not the issue its just thats since its over a year of this 'pedal fade' surely the level in the reservoir would have changed if the calipers were leaking or the fittings at the drums, wouldn't it?

I am seeking input in the order of troubleshooting for this. The car is 13 years old I mean I wouldn't be surprised if the master cylinder would fail internally. Plus I'm driving this car until the wheels fall off so putting money into it is not an issue.

Thx if anyone can help!

[northguest47]

Yaargs.. not a lot of ppl on this forum anymore. Well the work is done, thought I'd post a follow-up. I had the master cylinder in case it was needed, but it appears to have been the rears not getting any fluid, only the fronts.. the drums were in need of replacement anyway so that was done too.

[slayerized6]

Can be anything. Can be air getting into the system via the master cylinder or just a bad seal on the rear brake cylinder or front brake caliper.

[northguest47]

Ok slayerized6 you have answered questions of mine before too so thanks! I just returned the master cylinder, now what you are saying perhaps that should have been kept 'just in case' so to speak. I didn't know that air can get in but with no fluid getting out - thats the thing how the system didn't seem to have lost brake fluid. Now I'm thinking it was the master cylinder and the same dang thing is going to happen again.. well I will let you know. She's got new drums tho' (and an alignment today)

[northguest47]

The rears were dry, they sucked in air until it got to the 'other thang' and that one morning, that bubble incapacitated the entire braking system. Sooooo as I didn't but will now do every 4 months, bleed the brakes. Especially on older cars.

From me to you - that moment when there was no brakes was
fascinating.

And I am a good driver.