2001 GS430 with 168,000. Love this car, so when the Master died I had a dilemma.
Shelling out 600-700 dollars for a used complete unit was not what I wanted to do.
I read and re-read almost every post on brakes and the MC/ABS unit in this forum. I learned tons and also became really confused on how to bleed the system.
So, why did my MC die… after removing it from the car, I took the electric motor off and apart. Mine had suffered from the comutator being eaten by the brushes. It looked exactly like the photo posted by a member in a DIY. A chunk of the last few millimeters of copper had broken loose and was not completing the circuit. I searched for electric motors and replacement parts. No luck. So my hunt for a new complete ABS/MC unit had begun.
Ebay, Sewell, car-parts.com. What I learned was some listed the GS as being compatible with the SC430, LX470 and Toyota 4 runner. Some sites indicated the GS only was compatible with the GS. So now I have a question. Is it or is it not? Listings for used units for the SC430 were a few hundred dollars less. My motivation!
So we begin. Examining Sewell Lexus parts on line part numbers and diagrams I found that the bottom half of the unit shares the exact same part number. It is the top half of the unit that has a different part number. I own a SC430 as well, and examined my GS unit and the SC unit. They looked identical. Looking at the diagrams, multiple individual part numbers were the same on the top half of the units.
A closer look:
2001 GS 430
PUMP ASSEMBLY, BRAKE BOOSTER W/ACCUMULATO R
After comparing each individual part numbers within the same PNC 47201 I only found a few components that were labeled different. The two complete units I had in the garage looked identical less two brackets, so I decided to “Pull the Trigger” and ordered a used 2003 SC430 complete assembly from EBAY for $250 to install in my GS430.
My excitement built and the part arrived. The first thing I did was measure the booster plunger that the brake pedal attaches making sure they measured the same length, 6 inches both! Then I eyeballed the angle of the mounting plate and length of studs that go thru and up against the firewall. They looked identical. So in she went!!!
Everything Mated Perfect. No install Issue!
Now the Real Fun, Bleeding this system. I have bleed brakes in the past but this was my first time in a GS. The information on the forum was all over the place and contradicted each other, so I decided to go about it this way:
Car off. Pump pedal 40x steady pumps, pedal should get hard. Turn ignition to "ON" you should hear your pump cycle. It will go off after 25-30 secs. Leave "ON" pump about 5-7 times. Depress pedal open bleeder to FRONT PASS. Do this until no air is observed. Turn key to “OFF”. Pump pedal 40x. check and fill.
Turn key "ON" hear pump cycle. Wait till it goes off, then pump 5-7x and bleed FRONT DRIVER until no air is observed.
Pump 40x. key "OFF" check fluid level and fill.
Now do the back. key "ON" depress pedal open bleeder, the MC pump will do the work. Bleed until no air.
Key "OFF" pump 40x check and fill fluid. Key "ON" bleed the other rear until no air.
Last time. Key "OFF" pump 40x check and fill fluid to MAX LINE.
I was done.
The GS has never had a better brake pedal since I have owned her.
I put a 2003 SC430 complete MC assembly into a 2001 GS430, with NO PROBLEMS AT ALL!
I also saved a bunch of cash.
I hope this helps someone.
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The MC symptoms were all lights and the warning buzz. They stayed on then went off, did this all week. At times I lost the pedal completely. What clued me into the motor was a DIY MC repair post that showed the photo of the electric motor apart and the commutator eaten away.
The next time the lights and alarm were sounding I tapped the motor with a small hammer a few times. The motor spun pressure built up and the alarm and lights went away. Bad motor, so I began the hunt. No luck on replacement motor, had to do the whole unit.
No screaming noise at all. The first time it happened was when I pulled into my garage. warning lights and alarm. pedal went soft. The electric motor could not build pressure because of its internal problem. At over 160k I think the MC performed for 1 life of the car! Now she is ready for her second. The GS is quicker than my SC. It"s great for the daily errands.
You are awesome! I, too, own a GS and an SC. 99GS, 02SC. Can't part with either of them. I was just thinking the same thing, that the MBC parts MIGHT be compatible. Seems you felt the same and took "the informed chance". The prices are still hugely different...
(1) How is the SC installation holding up on the GS? Are the brakes still behaving after 5 months?
(2) Am I inferring correctly that all of your problems can essentially be attributed to a worn DC motor? So wish we could buy the motor separately...seems a rather simple, and cheaper, replacement.
What I learned was some listed the GS as being compatible with the SC430, LX470 and Toyota 4 runner.
I am wondering if you meant GX470, not LX470? The part number for the Pump Assembly (Pump and Motor only) is 47960-30030, and is shared by SC430, GS300/430, GX470, and 4Runner. The number for the LX470 is shared with twin sister Land Cruiser, as well as Tundra and possibly others.
I found a cheaper pump that was listed for a 2001-05 4Runner/GX470. I'm going to try it.
The challenge: can I replace the motor without disconnecting brake lines? First glance: no. But, sometimes, I surprise myself.