RX 350 - Brake Master Cylinder

[wtruck]

I have 2007 RX 350 FWD with 213k miles.  

The brake pedal has begun to slowly press all the way to floor when I am stopped at traffic lights and stop signs. 

So, I suspect the master cylinder is leaking internally.   I have checked brake hoses, calipers, fittings, underneath the power booster and master cylinder, and, not found any leaks.

Does anyone have any experience replacing a brake master cylinder on the RX 350 ?   I've not been able to find any videos that show the procedure, but, I did find a video for the Toyota Sienna that appears to be very close to what I'd expect.

 

[RX400h]

Have you had the brake lines purged of air? That would also cause a low brake pedal.

I have changed a master cylinder but in a 1989 car, and not anything newer. I would think a Sienna's procedure would be similar. As you may know, purging the master cylinder is necessary.

[wtruck]

I want to flush/purge the brake system before trying to replace the master cylinder.  I have a motive power bleeder, but, don't have an adapter for the Toyota/Lexus master cylinder.

Does anyone in the forum have any experience or success using either of these 3 different power bleeder adapters with the Lexus RX 350 ?

1. Motive 1101 Universal Adapter  https://www.amazon.com/Motive-Products-1101-Cylinder-Adapter/dp/B000Q6UHQ0
2. CTA 7041 Master Cylinder Adapter  https://www.amazon.com/CTA-Tools-7041-Adaptor-Toyota/dp/B005B4N6RY
3. Power Probe BA10 Adapter  https://www.amazon.com/Power-Probe-BA10-Adapter-Toyota/dp/B004IQ96RK

 

[wtruck]

And, in the tradition of the "American Way" (small, medium, and large) we always choose 'medium'.

However, in this case I chose 'small' (the cheapest) adapter....Motive 1101

It did work ok but I did experience some leaks.

I completed a brake fluid flush/purge.  All new brake fluid and a successful test drive around the block.   The next day a successful test drive to the doughnut shop.

But, on the 3rd drive, with my wife, to the Dairy Queen drive thru I began experiencing the sinking pedal again.

I have followed up with (2) additional brake bleeds of all 4 corners;, and, still I'm experiencing the sinking pedal.

I will probably attempt to replace the master cylinder now.

[RX400h]

Have you checked to see if Lexus technicians use a tool to cycle the ABS module? This was necessary for bleeding brakes on my 2001 Corvette, so I let the dealership do it.
Of course, it could still be your master cylinder.

[wtruck]

This has been my 1st/only Lexus (purchased from individual) and I've only had one experience with a Lexus dealership (oil leak).  I wasn't really impressed.

And, I'm pretty much hands-on and always trying to learn.

I'd had an issue with the front brake hose that would not connect back to the brake line (FP).  I have replaced front brake hoses/calipers/rotors/pads on this vehicle.

I have been wondering if air had gotten trapped in the ABS pump. 

I have bled the brake system multiple times....

• normal brake pedal pump (2 people)
• Motive pressure bleeding (twice)
• Vacuum pump bleeding (once)

I have no ABS dash lights on and have used my CenTech OBDII scanner to check for ABS error codes.  No codes found.  I found there are newer scanners that now activate an ABS Bleed to push any/all air from ABS pump/valves into the brake lines.  Then you follow with a normal brake bleeding..

Rather than paying a Lexus tech I'm considered/shopping for a newer OBDII scanner with the ABS Bleeding function.

• Autel Maxicheck Pro (wired)
• Autel MaxiAP AP200 'C' (wireless dongle/works with smartphone)
• Foxwell NT630 (wired)

 

[DannyLXD]

My friend is looking at a 2008 RX 350 with a similar brake issue. The brake maintenance was done by a local shop and recommended replacing it. It looks totally neat with a new set of tires from 4Wheelonline. We'll take a look at it this weekend.

[wtruck]

Decisions, decisions....

• replace master cylinder (@ shop $500)
• ABS bleed (@ shop $125)

Now the $500 at a local shop to replace master cylinder also included the ABS bleed.  But, to have an ABS bleed done on its own was $125.

And, to replace the master cylinder myself is $130.

If I purchase a scanner to attempt the ABS bleed on my own, most OBDII scanners with ABS bleed run about $150.

Well, I decided to attempt the master cylinder replacement, and, to DIY in my driveway.

Bench bleed went well, removal went well, and, even the install was not too bad.

 

Test drive around the block, and, yes I'm still having the (very) slow sinking pedal.....so I have to assume that the master cylinder is/was not the problem.

 

Now, buy a scanner.....or....take it to the shop just in case the issue is not the ABS bleed !!!!!

 

 

[RX400h]

It seems like the ABS bleed is only thing you haven't done, so let's hope it solves the problem. If you have an independent shop do it, you should be certain that they have done this to a similar vehicle without having any issues after the service.

[wtruck]

I've been reaching out to a few ole buddy's to see if I could borrow an OBDII scanner with ABS bleed functionality, but, all their scanners are like mine.

I made an offer on eBay for a unit with ABS bleed, but, we could not agree on my price!

Then, a couple of days ago we had a pretty good rain.  So, I went out and found a deserted road, sped up to about 45 mph and locked the brakes up....once, twice, and  a third time.

For the past (2) days the brakes have been working fine.....no slow pedal drop.

Next, I will perform an old fashion brake bleed with someone pumping the brake pedal and me under the car opening & closing the bleeder valves.

[RX400h]

Keep your fingers crossed!🙂