Master Brake Cylinder ?

[VetteMed]

I hope I didn't jinx myself. Driving home from work yesterday, my brake pedal was quite soft, with a long travel. Got home, and the forward reservoir was nearly dry (scary!). Today, I inspected the entire system, I can find no evidence of a leak (other than some bubbling caliper powdercoating near the RH front caliper bleeder screw.

Here's where it gets weird.

I bled all 4 calipers -- all the while checking for leaks (none). However, the LH front caliper really didn't give me a good solid fluid stream like the other calipers did, so I'm kind of scratching my head about that one. I did use a vacuum bleeding system, BTW.

So, I tightened the bleeder screws, topped off the fluid, and the brake pedal is now firm as it used to be. I don't get it at all. No signs of leaks anywhere. Perhaps master cylinder leaking into brake booster, only from the front portion of the cylinder? I don't know if that is even possible...

[scottfab]

Originally Posted by VetteMed

I bled all 4 calipers -- all the while checking for leaks (none). However, the LH front caliper really didn't give me a good solid fluid stream like the other calipers did, so I'm kind of scratching my head about that one. I did use a vacuum bleeding system, BTW.

Had a similar experience using vacuum on an Explorer.
Used the peddle to bleed them and the softness went away.

[gbrtng]

Originally Posted by VetteMed

I hope I didn't jinx myself. Driving home from work yesterday, my brake pedal was quite soft, with a long travel. Got home, and the forward reservoir was nearly dry (scary!). Today, I inspected the entire system, I can find no evidence of a leak (other than some bubbling caliper powdercoating near the RH front caliper bleeder screw.

Here's where it gets weird.

I bled all 4 calipers -- all the while checking for leaks (none). However, the LH front caliper really didn't give me a good solid fluid stream like the other calipers did, so I'm kind of scratching my head about that one. I did use a vacuum bleeding system, BTW.

So, I tightened the bleeder screws, topped off the fluid, and the brake pedal is now firm as it used to be. I don't get it at all. No signs of leaks anywhere. Perhaps master cylinder leaking into brake booster, only from the front portion of the cylinder? I don't know if that is even possible...

Wifey's 91 base car is leaking fluid from the front to the rear reservoir, so
that might be your problem. I just transfer fluid back where it belongs every so often.