pureshot

Yesterday replaced my MBC with a used one from 2003 GS300. Followed RyanV and others youtube how to and bleeding process.

process goes like this

1. install the unit and fill with dot 3 fluid
2. key off depress brake pedal 40 times
3. key on, motor will pump accumulator for up tp 40 sec. it should stop though fi it's a good unit
4. with key to on position pump brake pedal 20 times, buzzer comes on then should go off
5. check for leaks as lines tighten as needed
6. key on position bleed front right, then left caliper by pumping and holding pedal
7. brake pedal will get hard
8. bleed rear calipers by simply holding down pedal and cracing the bleeder,let some fluid out

It does exactly all the above, with one exception... Unfortunately no brake pedal pressure. Does this mean used MBC is bad? I have seen some other comments that only dealer can get MBC back online but that does not match Lexus forum commenets.

All the sounds and dash lights did exactly what the above and Youtube say. But no brake pedal pressure. Backs bleed with volume. Fronts bleed with little pressure???

Up the creek without a paddle. What to try next or do?

pureshot

Update. I tried to bleed the system again and this time it came online. Several post suggested that bleeding would be easier than it was. I just kept after it until all the air was out of the lines and now my replacement Master Brake Cylinder is just fine. No special tools and no dealer mechanic required. Thanks to everyone that posted.

It took 10-12 cycles to get the air out of the front lines. Until you do don't expect any pedal pressure.

Alphaman19

Now that your cherry's been popped, I bet you could do it in half the time now.

GS4302001

Anybody know if a master cylinder/booster assembly from a 2004 GS430 will work on a 2001 GS430?

I tried to post this earlier, but I don't think it worked (having troub's with my wifi connection).

pureshot

I put a 2003 Master Cylinder Booster assembly on a 1999 GS 400. Worked just fine. There is a sensor that you must removed from your older unit and place on the newer unit. With a big enough socket swapping the sensor was easy enough. You don't want a 2001 unit as the early failure rates were not resolved until 2003, I heard.. I don't have all the exact years memorized for when a redesigned happened. But I would say yes a 2004 works and the MCBA units that come off the SC models also work. To conclude if the unit looks like yours and is 2003 or higher from either a GS or SC it should work. You have the extra step of swapping the old senor off your unit to the new one. Bleeding takes sometime and must be repeated many times.

While it seems like a big job, it's really not. Getting the bolts off from inside the car can be tricky. Sharp metal brake peddle parts to watch out for.

I purchased mine off ebay, and added there insurance for $20 or so. If it had not worked I could have gotten my money back without fighting with the seller. I did not want to have to pay to ship it back.

sakataj

iTrader: (182)

yes, these are plug in play.... no swapping sensors on these. bolt in and bleed the brakes. the sensor swap is ONLY if you have a 1998-2000 model and you're going to a 2001+ model but since your going 2001+ to a 2001+ this is a plug and play swap

GS4302001

Well, by the time I got to You Pull R Parts, someone had beat me to it. However, at least now I know what to look for, i.e. 2003+ GS or SC. Thanks!

heybro

Kinda surprised with the high failure rates on these things Lexus hasn't had to do a recall of even offered us up a discount on the parts to fix. Normally, Toyota is a great company to work with and stands by their products?....

mrcreosote

this just popped up on YouTube. Very interesting. Looks like at least some of the time you can replace the brushes and core on the pump motor instead of the whole BMC unit.

scott802

Same here 1998 - Local repair shop wanted $2700+ (for part only) to replace the master cylinder part. I found one on ebay for $550. Labor to install is $400 so this forum potentially has saved me thousands already.
Great thread! Thanks much for this forum!

400gs99

2023 checking in. i was able to get the whole master cylinder abs brake booster assembly off a 2004 gs300 from a junkyard for $160 and replaced it in my 99 gs400 in about an hour. i still have to bleed the system. i cut the lines from the old sensor connector and soldered them to the new sensor connector. so far so good!