Brakes, A Puzzlement

[dabtl]

OK, the master cylinder was very low on fluid. Filled it. Pumped brakes to no avail.

Looked at all six wheels. No sign of a leak at any wheel. No sign of leak around the MC. No sign of leaks around the rubber brake lines. No sign of a leak around the metallic brake lines.

I have not checked the fluid level in the MC again. Should I?

Any ideas on what to do next? Thanks in advance.

 

[m-35tom]

if the air pack is leaking internally, the fluid will go into the vent lines and may even find its way into the fuel tank and not ever be seen as an external leak. what to do? if fluid in going down, you have a leak. pull all wheels and inspect, rebuild or replace the air pack.

 

[dabtl]

The air pack is a new shorty installed last year. But, anything can be bad I suppose.

 

[Nonotagain]

The air pack is a new shorty installed last year. But, anything can be bad I suppose.

Crack brake line at the master cylinder and see if the cylinder pumps fluid.

 

[Keith_J]

Pressurize the master cylinder with about 15 PSI of air. Sounds like the cups have retracted back. Not enough volume on the MC stroke to reseat the cups against the pistons.

 

[BugEyeBear]

Yes, you SHOULD check the M/C level again.

It could be empty again because you might have pushed the M/C res fluid into the lines.

& it might just not have reached the leak yet.

You also don't mention if the pedal is firm or soft?

& yes, it could be leaking into the airpack. You might be able to detect excessive fluid by draining the air tanks, but it could also be exiting the airpack via the vent line (as already mentioned).

 

[dabtl]

Thanks Keith. I went out pumped hard on the brakes and now they seem to be working again. Cups it appears to be. Fluid level was good. Oh, well onto the next problem with these things.

I will have to see how and where it may be leaking, however.

 

[Keith_J]

Do you have a breather cap on the MC or an air line?

Remember, silicone does not absorb water, it all sinks to the bottom. Look for minor corrosion in the WCs.

 

[dabtl]

I have an air line, soon to be replaced with a remote reservoir. All the WC and MC were put in new last year along with new shoes, springs, Hydrovac and rubber lines.

 

[m-35tom]

i still want to know how water gets into brake system with silicone fluid and no one can tell me............... i think this is just some ones paranoia

 

[Keith_J]

i still want to know how water gets into brake system with silicone fluid and no one can tell me............... i think this is just some ones paranoia

Humidity. When temperature drops, there can be condensation.

 

[JTugwell]

mine pretty much does the same thing. the fluid in the air pack makes sense because i always have oily residue on the hood. seems to be blowing out of the vent. same thing though. mc low, and no leaking lines or wheel cylinders. ill be watching this one. seems to be a pretty slow leak, but if brake fluid gets in the fuel tank will this hurt anything? i better order a new airpack.

 

[BugEyeBear]

Silicone fluid doesn't ABSORB water, but it can't prevent water/moisture from getting into the system.

With silicone fluid water tends to collect in certain points, causing some corrosion locally.

Even in a water tight system condensation can allow moisture into the system, eventually gathering in one point and causing corrosion.

IN SHORT, Silicone fluid has its benefits, & tends to last longer than DOT3, but there is no substitute for regular bleeding of your brakes. Removes air, dirt, & other contaminants, including water.

I bleed the brakes on my race cars before every race.
After a while it gets to be as easy as checking your oil or putting in gas.
Invest in a pressure bleeder!