Secretpraise27

I have a 2wd lexus rx300 that I bought used thinking it only had brake pads to change. Found out I had to work with the brake caliper pistons and check the abs sensors and get some suspension parts, get new boots installed on the rack and pinion and other things.

The main thing was that the front brakes were stuck and the abs, vsc and trac lights were on. Once I released the master brake cylinder from the booster to adjust the nut, this released the brakes and I thought I had fixed the issue. When I started driving, i noticed the abs light had shut off and it was braking fine. But it didn't last longer than a block. The abs light came back on and the braking problem continued. I disconnected the front sensors and even tried disconnecting the entire abs system and also bought new front calipers, but it still had my brakes locking up.

maxSteel

Welcome to ClubLexus

If the ABS light is on the ABS system is disengaged. You can read the ABS codes following this procedure https://www.clublexus.com/forums/rx-...ml#post9104458

If the front brakes released when you were working on the master cylinder maybe the problem is there.

Secretpraise27

The thing is that after working again with the master cylinder and putting it back, the abs light stays on and the brakes are still stuck. Do you think I should buy a new master brake cylinder?

maxSteel

You can have more than one problem. My ABS light has been on for about ten years. If you want to know why your light is on follow the procedure to read the codes.

I can't say of your master cylinder has an issue but if disconnecting the brake lines from it relieves the stuck condition it would seem likely.
I doubt the individual lines to the front wheels both failed at once.

salimshah

I speculate the problem is in return flow of the brake fluid. When it is pushed down there is enough pressure by the piston n master cylinder but the return is by run out in the rotor.

I would open up and close each fitting progressively down the line from the master cylinder and see if the master cylinder drains under gravity. You can aid gravity by low pressure on top of the master cylinder. Most notorious are the rubber lines which swell up internally.

Salim

sktn77a

iTrader: (2)

I had a similar issue. No lights on but the caliper was stuck and it turned out to be the hoses. Didn't believe it at first but replacing the caliper didn't fix it - new hoses did.

maxSteel

I've had it happen too, but what are the odds of both front brake lines failing at once?

salimshah

Very reasonable argument and that is why I suggested starting at the source and work down towards the end. If it was inly one wheel, then the trouble shooting should start from the wheel back.

I would definitely test out the flow issues before tracing the ABS warning. ABS tracing should start with good battery and AC ripple on the alternator output.

Salim

Secretpraise27

I'm sorry for taking long to respond. Finally got the master cylinder and after putting it I reset the abs lights and for a good moment was celebrating the awaited relative of finally fixing abs getting to enjoy my vehicle. But, sadly, after driving for a few minutes, I had to return back home to feel that same feeling that I had in the beginning.
I had also checked the ohms for each speed sensor and they check out fine. I don't know how to check the file of the brake fluid (I think Salim had shared) . Is that like bleeding the brakes? The weird thing is that both front brakes get stuck and don't know if the brakes hose will fix the issue. I'm thinking of going with that though. What do you guys think? Thanks for all the help.

salimshah

I suggest the following test to ensure free flow and return of fluid.

Ensure the master cylinder is full.
Connect a hose to the bleeder and make sure the other end of the hose is in a ~2" standing fluid in transparent bottle. Mark the level.
Crack open the bleeder valve ~ 1/2-3/4 turn. Observe any change in the level of b fluid in master cylinder and the bottle. This process is also known as gravity bleed. If nothing flows there is a potential of blockage in that path.
Move to the next wheel.

I referred to purging the brake fluid. It is a process of bleeding old fluid out while constantly adding new fluid and not introducing air in the system. Although I have not used different colored brake fluid but they are available to recognize the old has been flushed out.

When you replaced the master, did you purge air? I would guess yes. And how did the process go? Was it easy to pump out the fluid? Did you observe any abnormality in the offending side? If the answer is no, then replacing the ABS block seems like the likely fix.

I would ignore ABS light for now and focus more on brake functioning as normal.

Salim

Secretpraise27

When I installed the master cylinder I did press the brakes and then held the ports of the two oil lines while the other person released the brakes. I did that three times and secured the nut before releasing the pedal to get air out. Then I bled the brakes

salimshah

Sounds like the right procedure, but did the clean fluid eventually came out with lot of energy or was it dribble? I trying to establish if the fluid is flowing freely. Also if enough of the fluid was pushed out, you have purged the old fluid.

Salim

Secretpraise27

Looking into other threads about the brake issue I read two people talking about the alternator. And I had forgotten that I bought a new battery and after a few days it had lost the charge. I thought it was an open door, but it wasn't because it lost charge again. I ordered an alternator after checking that the battery wasn't charging when turned on. I'll let you guys know what happens after I install it.

Secretpraise27

I'm back with updates. Installed a used, but tested abs unit and bled all brakes calipers. After driving and feeling like I got it fixed, the brakes began feeling hard and the vsv and abs lights can back on. And just like before it started jamming my front brakes(since my lexus is 2x4). I got the scanner tool and it read error code C1246 master cylinder pressure sensor. I can't find that anywhere and YouTube doesn't help at all either. It also showed C1223 abs control system malfunction. Can anyone HELP?

Secretpraise27

I'm back with updates. Installed a used, but tested abs unit and bled all brakes calipers. After driving and feeling like I got it fixed, the brakes began feeling hard and the vsv and abs lights can back on. And just like before it started jamming my front brakes(since my lexus is 2x4). I got the scanner tool and it read error code C1246 master cylinder pressure sensor. I can't find that anywhere and YouTube doesn't help at all either. It also showed C1223 abs control system malfunction. Can anyone HELP?