Master Cylinder Fail - can you help verify?

[Mike_95]

Hi guys,

95 camry 4 cyclinder, non-abs, 170k miles

- brake pedal goes all the way to the floor. can stop barely at very end of pedal travel.
- small amount of fluid in the rear reservoir, none in the front reservoir.
- no leaks observed on ground, all brake lines replaced last winter and fluid flushed at that time.

Is this an indication of an MC fail? (Im pretty sure it is)

It looks like the fluid may have gone into the booster since its not leaking onto the ground. If that is the case, how best to clean out the booster?

many thanks,
mike

[pmesfun]

Definitely sounds like a bad master cylinder, same thing happened on my friends Tacoma and the brake booster had to be replaced as well because the brake fluid damaged the seals. I think we got A1 Cardone reman master and booster.

[Pvt-Public]

The easiest way to verify if the MC is leaking is to pull the vacuum supply line to the booster. If there is any fluid in the line the MC is bad. You can also crack the MC loose from the booster and see if there is any fluid behind it. If it has been leaking into the booster you should replace the booster also since brake fluid will damage the seals in it.

[Mike_95]

Thanks guys!

I pulled the MC from the booster just now and I can't seem to see any of the missing brake fluid anywhere. No sign of it in the vacuum lines or between the booster and MC.

i checked undercar fairly throughly for any signs of brake fluid leaks and saw nothing. I am missing about a pint of fluid, so it had to go somewhere. I refilled the reservoir and pumped the brakes, and now there is no visible loss in reservoir fluid level after pressing the brakes 10-15 times. The brakes are spongy since there is air in the system, but it feels like I could bleed and it would feel fine.

I even checked undercar and all the connection points again - not even a trace of a seep from the brake lines.

Any ideas for further checks? I definitely want to root cause where the fluid has gone.

-Mike

[Stillrunning]

Originally Posted by Mike_95

....so it had to go somewhere.

I'm wondering if it's still in the booster. The vacuum line is above the M/C connection to the booster so fluid would run down inside and not necessarily through the vacuum line. The vacuum is dead headed so not really any flow, and it's flow that would draw fluid into the vac line.

[fenixus]

if the brake fluid made its way into the booster behind the vacuum seals, then the engine vacuum sucked it inside the engine...

question#1 is why it doesn't do it anymore? there should be a visible leakage on the back of MC piston if that was the case.

I would give it a few dozens of really strong brake pedal depressions and check for leaks under car while or after depressing it.

you might wanna try bleeding the system now and see if you are able to get all the air out? pint of fluid doesn't just disappear like that ...

[pmesfun]

Originally Posted by Mike_95

Thanks guys!

I pulled the MC from the booster just now and I can't seem to see any of the missing brake fluid anywhere. No sign of it in the vacuum lines or between the booster and MC.

i checked undercar fairly throughly for any signs of brake fluid leaks and saw nothing. I am missing about a pint of fluid, so it had to go somewhere. I refilled the reservoir and pumped the brakes, and now there is no visible loss in reservoir fluid level after pressing the brakes 10-15 times. The brakes are spongy since there is air in the system, but it feels like I could bleed and it would feel fine.

I even checked undercar and all the connection points again - not even a trace of a seep from the brake lines.

Any ideas for further checks? I definitely want to root cause where the fluid has gone.

-Mike

Its probably in the brake booster, we couldn't tell until we took it out and dumped out all the fluid in the booster.

[Mike_95]

Thanks again guys for the replies.

There was absolutely no sign of fluid between the MC and booster. It was dry - there was even grease there on the pushrod from the booster. It really didn't seem like any fluid had flowed through there.

I'll have an assistant help me today depressing the pedal while I search again for leaks. I did about 20 strong pushes on it yesterday and now the fluid level does not go down.

As has been said the fluid had to go somewhere....

Is there some creative way to check for fluid in the booster without removing it?

Im totally perplexed

[Mike_95]

I bled the brake system today and flushed in new fluid. I had a helper so I could bleed the old fashioned way and really cleaned it out - 10 pedal presses per caliper/drum. There was no sign of fluid anywhere on any of the fittings - checked every single one.

My indy was the last one who touched the system in the winter replacing rusted brake lines. They did not properly flush the system - the brake fluid coming out of the bleeder screws looked like swamp water.

Just drove 25 miles home with it....it's fine now. Locked up the wheels going 45 mph no problem.

Im going to watch fluid level like a hawk over the next week. I'll report back.

In other news I found the rear subframe in the back is very very rusted. Like poked huge holes in it rusted. That's for another thread.

[fenixus]

interesting ... so the indy shop left the system filled with half fluid half air?
did they flush the rear brake lines at all? they should be done first before the front. Correct bleeding order is furthest from MC to nearest, RR->RL->FR->FL.

if the former fluid turned rusty so quickly that may be a sign of a corrosion happening somewhere (MC piston?).

also, have you noticed any "dirt" or tiny black particles while flushing the old fluid out? those are signs of rubber seals going out.

keep an eye on it. I would hate to see a thread describing this car having some front end collision ...