213374U

I ran into an issue a couple months back where the rear seal on the brake master cylinder failed, dumping fluid into the booster and causing almost complete loss of brake pressure. Got it towed home and ordered a new master cylinder and replacement booster. The booster came from a salvage yard in MN as the only reman/aftermarket option I could find that was guaranteed to fit a 94 w/o TRAC was close to $600. Repair went smoothly, but the booster hisses in the cabin when the brake pedal is halfway depressed so a seal or the diaphragm itself is failing. I still have good brake pressure but can't lock them up like I used to. Gotta hunt for another booster but thankfully it's drivable.

Does anyone know the difference between the TRAC and non-TRAC boosters? I can't seem to find any details anywhere but buying a TRAC compatible booster would save me close to $400.

YODAONE

Any yard pull will have same tired rubber seals.

Purchase master cylinder rebuild kit from Lexus. There is a sequence and procedure for removing and installing the plunger/seal assemblies...if you do it wrong you will destroy the bore...bring master cylinder to dealer for install of rebuild kit.and purging cylinder of air (adding g brake fluid...if you attempt to pump it dry you can ruin new seals)


Rebuild kit still available. bottom image. Also purchase rubber grease.

Be sure and provide your VIN to dealer when purchasing rebuild kit.

213374U

Thanks @YODAONE , however I was able to get a good reman master cylinder and have no problems with that. The issue is with the booster, and the sound seems to be coming from where part #47275 in the above diagram is located. If that was worn/damaged could that cause the hissing? Or is there another seal in that general area that I should look into?