I have what seems to be a common issue in these cars. Done research on it and pretty sure I need a master cyl assembly. Just wanted to get the Lexus community's take on it for the best way to go about fixing it because the part is expensive new. And as common as this is, how can I trust a used one?

My issue doesn't seem to be a serious as most. I only get the lights and buzzing on first start up daily for about 5 seconds. Then once the accumulator pumps up, it goes away and will never happen again. Obviously the system is loosing pressure over night and is better once it's pumped back up. This tells me that electronically everything is working fine. It's an issue on the accumulator side of things. Is there a write-up or diy or known way to repair this part of the master? Seals? Epoxy on an area?

This issue has been present since I bought the car and hasn't ever changed or got worse. I'm more for fixing rather than replacing if at all possible.

 

This could be a number of things, you may have a slow leak internally and after pump primes itself then it's back to nominal pressure. You could also have air pockets in the line that would cause this.
A lazy pump or low on nitrogen pump could also be an issue.
There are some DIY on how to replace the accumulator but I would start by doing a proper brake bleeding with the 40 pump procedure.

 

I will give the bleed a try, why not, maybe for some reason this system really needs it. However I am a tech and very familiar with what air in the lines feels like. I have a solid peddle at all times, even when the lights and warning come on first thing in the morning. No squishy peddle or loss of braking whatsoever. I can hear the motor come on and its a good strong sound, my thoughts are that the motor is working fine. It only takes moments to pump it up. I think it's pretty clearly a pressure issue in the accumulator. I've never worked on one of these systems before. I've heard of the nitrogen charge, have't looked into it. Been busy with other repairs on the car I consider more important at the moment. But now I'm starting to turn my attention to this issue. So is the accumulator filled with nitrogen? How does that work?

 

If I was to replace just the accumulator, can it be done in the car without removing the master? Is the accumulator what is filled with nitrogen? Here is a link to what I'd like to replace. It does say in the description that it is drained. Not sure exactly how this system works. Would that mean drained of brake fluid? Or drained of the nitrogen? How would one go about refilling it after installing? And do brakes even function without nitrogen in the accumulator?

 

Looks like you can do it in the car:

https://www.clublexus.com/forums/gs-...lpppppp-2.html