Problem:
Brake pressure loss after a few days. Brake pressure can be built with the car off, once car is started, brake pressure gone. No leaks found, fluid in reservior still full.

Attempted Fixes:
Replaced Master Cylinder
Replaced Brake Booster
Bled brakes
Flushed system


Something is letting air in and I can't find it. During hard braking while testing it, there's minor fluid that appears around the bleeder screws...but, that's it. I figured if there was an open in the system, fluid would leak out of it when it's just sitting.

 

How are the caliper pistons/ seals? It's possible that a damagaged cylinder wall coupled with a damaged seals could definitely allow an air leak. Not extremely likely however.

Anyway if there's fluid at thge bleeder screw, then I would definitely reexamine that. Just because fluid isn't coming out doesn't mean air isn't going in. Have you examined the hardlines leaving the MC?

 

Check the bleed screws to see if the taper is undamaged. Some people over tighten them, causing leaks.

Kirk

 

I had this problem before. It was the MC.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Littleton &raquo;</TD></TR><TR><TD CLASS="quote">I had this problem before. It was the MC.</TD></TR></TABLE>
It was replaced.

The hardlines from the MC would have fluid on them if they leaked, correct?

There's no fluid loss when it sits. I'm guessing it's the calipers... I'll find out when i put my stock calipers back on the car and see what happens.

 

Where is the air? When you bleed, is it at the bleed screws? That should tell you that the leak isn't at the M/C or with the booster.

Looks like you might either have to tighten up some stuff, replace some wheel cylinders (if ya got drums), or rebuild some calipers.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by madhatter &raquo;</TD></TR><TR><TD CLASS="quote">replace some wheel cylinders (if ya got drums)</TD></TR></TABLE>
This could be the case too. But, wouldn't there be fluid if they were worn/leaking?

I know when I bleed the rear drums, there isn't much fluid that comes out, if any. But, they work...

 

Only when you use them. Pull the drum and check for fluid sprayed everywhere inside.
I replaced mine. The manual suggests to replace both at the same time. They are 12 bucks a piece at AutoZone, and are one less thing I need to worry about now.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by madhatter &raquo;</TD></TR><TR><TD CLASS="quote">Only when you use them. Pull the drum and check for fluid sprayed everywhere inside.
I replaced mine. The manual suggests to replace both at the same time. They are 12 bucks a piece at AutoZone, and are one less thing I need to worry about now.</TD></TR></TABLE>
Yeah, i'm gonna replace mine too... eh.