98 GS 300 Brake Master Cylinder - Club Lexus Forums


98 GS 300 Brake Master Cylinder

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Old 04-02-14, 06:29 PM   #1
Aerostar
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Default 98 GS 300 Brake Master Cylinder

Hi Guys,

Just did the timing belt job. The Schley tool made the job SO much easier! Got the O-ring kit from Jeff Tsai for the VVTi cam gear and now with new NGK iridium plugs and a new set of plug wires everything is just amazing.

NOW I've got the Brake Master Cylinder re-pressurizing too often and its kind of loud so after searching the forums I ordered a new BMC unit- only it does NOT have the little electric motor on the bottom and the "soup can shaped" accumulator (I think that's what its called.)

I was wondering if anybody had any experience with scavenging the old "bottom half" and installing it on a new master cylinder?? I'm hoping I can do it because if not I may have to buy a complete new/used unit. Do I need any o-rings, etc? Anybody have a manual??

Many thanks for any help.

Rich
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Old 04-06-14, 06:39 PM   #2
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Default BMC replacement

Well,

I changed it out. Got everything to hook up. Now I just need to bleed the system out and flush the brake lines and bleed them too. I'll look around for a DIY brake bleed for the 98 GS300.

Lucky it was the new style. Had to go to a buddy's house and switch the sensor because it takes such a deep well socket.

Whew!
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Old 04-06-14, 06:56 PM   #3
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Cool, where did u get that master cylinder? These things are very problematic on the 98-00.
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Old 04-07-14, 04:49 PM   #4
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Default 98 Master Cylinder

I got it on E-bay. I got got the brakes bled today with the help of my lovely Mrs. BUT I still get the "chirping" . Brakes are not soft and stop well but I get the chirping near the end of the charge cycle. Think I need to change the charging can and the motor too? Or is there a way to bleed it better to make sure that's not the problem. Possibly bench bleed before re-installing. I hate to have to take it off again.

Thanks.
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Old 04-07-14, 05:35 PM   #5
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I have had that annoying chirping sound on 2 master cylinder/abs pumps, both of them on 98-00 models. I think the chirping is caused by the motor, I mean what else can make that sound. Don't think the ABS modulator (actuator valves) are making it.

Bench Bleed, I guess you can fill it up with brake fluid and don't hook up the lines and pump it a bit.

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Old 04-07-14, 11:24 PM   #6
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I tried bleeding it at the bmc connectors but still the "chirping".

Broke down and ordered the $1100 booster motor/accumulator assembly- OUCH.

Motor seemed to run and pressurize but would Chirp at the end of the pressurization.

Will take it all back out, install the motor and accumulator and put it back on.

Hope it works!
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Old 04-09-14, 09:06 AM   #7
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Damn that hurts .. Have a sound coming from right behind my firewall soon as I turn on engine and sometimes when I break is that same sound you were hearing ? Have 01 with 90k on it changing out my rotors and pads in week or 2
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Old 10-10-14, 11:23 AM   #8
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@AeroStar - I'm getting that chirping sound also (really embarrassing when someone else is in the car) .

Question: Did you have any issues putting the new pump/accumulator onto the new bmc unit?
I see that there's a red plastic sleeve/cover on the fluid line connecting the pumpaccumulator to the the bmc unit.
I think I can disconnect it w/o issue but wanted to see if you had any issues.
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Old 11-04-14, 08:25 AM   #9
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Did you install a 01+ brake master?

I've got the chirp too on my 99' Gs400. Brakes work fine though, does the chirping indicate an actual problem?

It just sounds like it's coming from under the dash when I tap the brakes sometimes. I can be in park and tap the brakes and after I release the pedal I'll hear this audible screech chirp under the dash.

I do have an opportunity to buy a complete 2001 brake master unit today for $200. I want to make sure I can actually install that unit on my 99 Gs400. I keep reading about a sensor that needs swapped out, but I can't find the thread detailing that info.

Thanks,
Ryan
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Old 11-04-14, 11:36 AM   #10
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Any 98-2005 bmc from any GS/SC will work.
As for the pressure(?) sensor, you actually have to disconnect it before you take the old unit out.
I'm not sure what year the configuration of the switch changed, but just compare your current one and the new one. If they're different, just unscrew you old one and put it in the new one. You'll see what I mean.
It's the kinda thing where a picture is worth a thousand words
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Old 11-04-14, 02:22 PM   #11
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Yeah no kidding. One guy made it sound like you have to take the entire brake master assembly apart before you can get a wrench around it. I just want to confirm because I'd rather not have to disassemble the entire unit.
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Old 11-05-14, 05:55 AM   #12
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Nevermind, looks like a large socket will easily pull that front facing sensor.
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