After 10 years of ownership, and 147,000 miles, I'm very familiar with my car's stopping characteristics. Today I noticed that my brake pedal feels spongy and I can feel it sinking slightly while depressing it at a stop light etc. I did have my brake fluid flushed last year. I'll assume it's most likely my master cylinder which is quite pricey for the OEM (approximately $300). I'll be visiting my Indy this week to have it further diagnosed. I've always gotten OEM replacements for all my parts, but I was just wondering if any members have replaced their master, has anyone used anything other than OEM? If so, what brand and how has it performed? Thanks all.

 

Hi, I replaced with non OEM one. The brand is dorman. Replaced ~ 5-7k miles ago. So far so good.

 

Thanks beercan. How many miles were on your car at time of replacement?

 

May I suggest another full brake flush including ABS pump to remove all the air? One thing to keep in mind that LS430 master cylinder is fairly reliable, unless the brake fluid dropped and caused internal damage.

Please describe the braking characteristics. Does the pedal pulsate? Is it easily going downwards or it makes an attempt to become stiffer somewhere in the middle way? Do you feel braking power has been substantially decreased and it becomes more and more difficult to stop the car in a predictable manner?

 

Braking ability has not been affected. There is no pulsating. I even attempted a few emergency stops. All performed well. The pedal has a tendency to sink very gradually after stopping. It does not go down to the floor. It just sinks a few inches or so which it had never done before.

 

I assume the fluid level hasn't changed at all?

 

You may also consider performing the on-vehicle inspection below to make sure your brake booster is functioning properly.

 

Thanks RKW7780 Great Info! All good with my booster.

 

Level is fine. Thanks.

 

Since it's not the booster, the culprit is likely to be a failing gasket or O-ring within the master cylinder. Please take a look at the attached for procedures to make the repair.

 

Since you already checked the booster next thing I would do is carefully go through the ABS bleed procedure a few times to rule out that module, if that doesn't work it would still be my top suspect since bad masters are usually a really bad pedal drop and loose fluid after a while. However it is much easier to replace than the ABS block

 

It's not your abs I am 100% sure it is not your abs so do not worry about it also there is no air in the brake lines air does not magically appear in the lines unless there is a hole which you would have noticed because there has been no fluid change in the reservoir.

The o ring in the master cylinder sounds like it is these cars are almost 20 years old so it is totally normal for o rings and things like it to dry out.
Below there is a link for masters there $70-$110 on average new oem is like $600
https://www.ebay.com/sch/i.html?_nkw...430+brake.TRS0

maybe a piston is stuck or not engaging on the caliper take them off and have some one step on the brake to make sure they move freely.

 

He allready said he did panic stops that pushes the fluid through the abs if there was bubbles in the abs it would be in the lines after the panic stops.

 

No not necessarily, I have dealt with more than a few cars that had air in the module requiring 5-8 bleed procedures and two that had outright piston failures internally. But whatever, I agree throwing a master at it at this point is the easiest option

 

Used an OEM rebuild kit on 1999 LS400:

https://www.clublexus.com/forums/ls-...r-rebuild.html

The initial challenge extracting master cylinder is preventing brake fluid from contacting painted surfaces... redundant covering is important and have ready a bucket of soapy water with sponge. (If taking to dealer or indy, take numerous high resolution images of painted areas surrounding the master cylinder.

Before removal, extract as much brake fluid from master cylinder as possible.

Am not an advocate of aftermarket master cylinders or rebuild kits.

In either scenario, use OEM.

While some Indy shops may take issue with installing your provided aftermarket parts (insurance or profit), they have zero reason to refuse OEM purchased.
If you do not take initiative, 9 of 10 repair shops will make the decision for you by using random aftermarket parts. Made in China does not yet nspire the same confidence as Made in Japan.

The condition of the bore of the master cylinder will determine whether you rebuild or replace...so bore inspection requires specific measurements.

On my 1999 (175,000 miles), used the finger test..so yours should be fine.

Unsure if your LS430 requires pressurization of the master cylinder reservoir with special service tool to bleed the anti-lock brake solenoid block, but found it made bleeding the system a one-person job.
Acquired mine from AST Tool.