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Master Ran Dry, Spongy Pedal Now


lex4me
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Okay, so I was doing my replacement brakes on the front of my 91LS and I cracked the brake line fitting to loosen it prior to removing the old caliper. I thought I had re-tightened it enough after its removal from the slider pins, but evidently not since when I came back to work on the car more after leaving it overnight I had brake fluid on the floor and the master cylinder had drained to the point that the front-most hole leading into the master was at least partially exposed. I immediately thought that it was time to bench bleed the master (grrr), but then the local auto parts guys said that that was only the case on cars with an ABS motor directly hooked up to the master cylinder. Since mine wasn't that way, they said, I didn't have any worries.

Well, the car is back together again and wouldn't you know that I have a soft, like very soft, pedal (this after bleeding the brakes with the new calipers). I was going to try re-bleeding at the two front calipers to see if that would help, but am skeptical.

Questions:

1. Does that front port feed the front or back brakes (i.e. which ones possibly have air)?

2. Is bleeding at the calipers a waste of time and fluid until I get the master bench bled?

All thoughts appreciated.

Thanks!

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You don't need to bench bleed the master. At worst you can do a bench bleed in position on the booster - the master doesn't care where it is.

You may be able to fill the master, open the caliper bleed screw and wait until about half the reservoir gravity feeds to the caliper. It's also possible you'll have to bleed at least the front axle, or all four corners.

I don't know on the Lexus, but normally the primary piston, the one closest to the driver, feeds the front brakes. But squeak some fluid out of both bleeder screws anyways.

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You don't need to bench bleed the master. At worst you can do a bench bleed in position on the booster - the master doesn't care where it is.

You may be able to fill the master, open the caliper bleed screw and wait until about half the reservoir gravity feeds to the caliper. It's also possible you'll have to bleed at least the front axle, or all four corners.

I don't know on the Lexus, but normally the primary piston, the one closest to the driver, feeds the front brakes. But squeak some fluid out of both bleeder screws anyways.

I would suggest returning that master and getting one from the dealer..More money I know but I have had SEVERAL faulty masters right out of the box from an auto parts store-thats my 2 cents.......

Best wishes,

lexushead

ASE Master/L1

Toyota/Lexus Factory Certified Master

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I went to bled them starting at the driver rear and heard a pss noise from the driver front caliper when my son pressed the pedal. A little investigation later revealed that the connection from the brake line to the new caliper was leaking horribly.

I remembered when I replaced these calipers being uncomfortable with the thickness (double, really) of the replacement copper washers that came with these new calipers from Autozone. I also remember when I used them, being uncomfortable with how few threads I had actually holding the brake line to the caliper as a result of the increased thickness (double the thickness times two washers means not much bolt length left). I remember feeling like the threads were about to give way when I first assembled it so didn't tighten further. To correct the leak, I ended up re-using my old copper washers. I certainly wasn't comfortable doing this (always heard you were supposed to replace them), but the leak is gone now.

My pedal is much stiffer now (imagine that), but it still feels like there is some air in the system (the brake pedal drops perhaps 30% before truly doing anything, but removing your foot from the pedal momentarily and then putting it back on results in a firm pedal that is maintained throughout a gradual or hard stop). Plans are to go ahead and replace the ultra thick washers on the passenger side front wheel just because and then rebleed the entire system.

So...beware of ultra-thick brake line washers from Autozone-sourced calipers on your Gen I LS.

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