C4 Brake Master Cylinder-Missing brake fluid

[Dale P.]

OK, have a very interesting question. Pulled the the Corvette out of the storage garage the other day. Drove it home (a few miles away) by the time arrived home - very spongy brakes opened the hood and checked brakes. Of course all the expected dash warning lights were on. removed the brake fluid cap and to my surprise NO FLUID! NOT A DROP! So I Filled the reservoir, of course brakes still need to be bled. I see NO fluid any where from anything. The fluid is still in the reservoir. I have started the engine many times left it run. I pumped the brakes and no fluid leaking any where, remember I still need to bleed the brakes so they are a little spongy.

Went back to the storage garage and NO fluid on the floor, No fluid under the car since it has been home. I don't want to waste my time bleeding brakes if I need to change something.

So the question is where the heck did the fluid go?

[Jim T.]

Re: C4 Brake Master Cylinder-Missing brake fluid

When was the last time you inspected the brake fluid in the master cylinder? I could of been low to a slow leak over a good period of time. Once you remove the wheels and inspect the brake hoses and calipers, and also the back part of the rims you might find the leak. Fluid can also leak out of the rear of the master cylinder.

[Dale P.]

Re: C4 Brake Master Cylinder-Missing brake fluid

When was the last time you inspected the brake fluid in the master cylinder? I could of been low to a slow leak over a good period of time. Once you remove the wheels and inspect the brake hoses and calipers, and also the back part of the rims you might find the leak. Fluid can also leak out of the rear of the master cylinder.

the last time to fluid was checked was right before it went into storage . remember I stated that not a drop of fluid anywhere on anything, including the floor of my storage garage. I top off all the fluids right before she went into storage

[Michael W.]

Re: C4 Brake Master Cylinder-Missing brake fluid

The missing fluid might be inside the power brake booster.

[Dale P.]

Re: C4 Brake Master Cylinder-Missing brake fluid

any easy tricks to determining this? I know remove the check valve, but I do not believe I can see in there

[Patrick H.]

Re: C4 Brake Master Cylinder-Missing brake fluid

The missing fluid might be inside the power brake booster.

Yep. This happened with my wife's Saturn Outlook. I wondered why the level kept dropping, and after doing a bit of Google checking found that it likes to leak out the back of the master cylinder into the brake booster.

I bought a new MC, and when I swapped it out I also sucked all of the old brake fluid out of the brake booster. I then followed that with some denatured alcohol which I also sucked out and dried inside the booster. I then put it all back together, and life is good again.