Sinking brake pedal even after replacing master cylinder
01-20-19, 12:14 AM
#1
Pit Crew
Thread Starter
Sinking brake pedal even after replacing master cylinder
Hi everyone,
Recently bought my first car a few months ago, a 2001 ES300 with only about 85K miles. Absolutely love everything about the car, except for my one issue. The brakes. More specifically, the brake pedals keep sinking even after the master was replaced and the system bled.
When I had the car inspected, my mechanic noted that there was something off with the brakes, and it was likely that the calipers were seized somewhere, that was fine, I ended up fixing the 2 front calipers that were completely seized myself, no issues there. What did happen after though and before, was that the brake pedal was slowly sinking to the floor when i used the brakes. The point of engagement was maybe when the brakes were pushed about 60-70% of the way, but there was some resistance and it never completely sunk to hit the floor.
So, off to the mechanic shop it went, as it was far too cold to work on it myself. I brought it in to get the sinking pedal checked and do replace the brakes if needed, which I knew the pads were almost completely worn out from the inspection done, though I was completely expecting the Master cylinder needed to be changed. To my surprise, all he did was replace the rotors/pads and bleed the system. For a bit, it seemed like it fixed the issue, but then the pedal slowly began to sink again, with the point of engagement returning to what it was like before. The mechanic also told me that he checked over the brake lines and found no leaks, so there should be no issues there.
The next time, I brought him a brand new master (Brand was Beck&Arnley) and told him that the sinking pedal issue was still occurring and bleeding the system before had only temporarily fixed the issue. So he replaced the master and bled the system, but that still didn't not work. He said there might be some issue with the ABS system and told me he was going to try replacing it why a different brand of master cylinder to see if that would fix the issue, if it didn't he would look for a used ABS actuator to replace. Surprisingly, at the time at least, it appeared that replacing it with a different master cylinder did fix the issue. The brake pedal no longer sunk to the floor, and it engaged very early on, and had the expected amount of resistance when it was pressed on. Seemed like all my issues were solved.
That was until tonight, where we had a huge snowstorm and the ABS engaged several times, that the brake pedal began to sink again. When the ABS first engaged, it caused the pedal to start sinking to the floor after. Then, it engaged again and suddenly the pedal was no longer sinking when being pressed again. It seems to be heavily related to the ABS engaging.
I'm not sure what to do now, as it very frustrating to have a sinking brake pedal, even after replacing the master cylinder essentially twice. I've read that the ABS System lines also need to be purged, but you have to have the Techstream software to do so. Which means that I would have to go to the dealership in order to do that, which would probably cost a lot of money, or get a Techstream cable/ adapter and use that. Does anyone have any experience with this? How much would a dealership typically charge to do the bleeding, can I even go to the dealership and tell them that I only want the brake lines/ABS system to be purged? (I've never been to a dealer for service, so I'm not sure if that's something that is possible).
If I don't go to the dealership, and I bought a Techstream cable/adapter and got the software, would I need to open up any brake lines for the ABS to allow the air out, or do I simply run the ABS bleeding utility and let the software do all the work?
Or is it even possible that it has nothing to do with the ABS System? Thanks in advance for any help!
Recently bought my first car a few months ago, a 2001 ES300 with only about 85K miles. Absolutely love everything about the car, except for my one issue. The brakes. More specifically, the brake pedals keep sinking even after the master was replaced and the system bled.
When I had the car inspected, my mechanic noted that there was something off with the brakes, and it was likely that the calipers were seized somewhere, that was fine, I ended up fixing the 2 front calipers that were completely seized myself, no issues there. What did happen after though and before, was that the brake pedal was slowly sinking to the floor when i used the brakes. The point of engagement was maybe when the brakes were pushed about 60-70% of the way, but there was some resistance and it never completely sunk to hit the floor.
So, off to the mechanic shop it went, as it was far too cold to work on it myself. I brought it in to get the sinking pedal checked and do replace the brakes if needed, which I knew the pads were almost completely worn out from the inspection done, though I was completely expecting the Master cylinder needed to be changed. To my surprise, all he did was replace the rotors/pads and bleed the system. For a bit, it seemed like it fixed the issue, but then the pedal slowly began to sink again, with the point of engagement returning to what it was like before. The mechanic also told me that he checked over the brake lines and found no leaks, so there should be no issues there.
The next time, I brought him a brand new master (Brand was Beck&Arnley) and told him that the sinking pedal issue was still occurring and bleeding the system before had only temporarily fixed the issue. So he replaced the master and bled the system, but that still didn't not work. He said there might be some issue with the ABS system and told me he was going to try replacing it why a different brand of master cylinder to see if that would fix the issue, if it didn't he would look for a used ABS actuator to replace. Surprisingly, at the time at least, it appeared that replacing it with a different master cylinder did fix the issue. The brake pedal no longer sunk to the floor, and it engaged very early on, and had the expected amount of resistance when it was pressed on. Seemed like all my issues were solved.
That was until tonight, where we had a huge snowstorm and the ABS engaged several times, that the brake pedal began to sink again. When the ABS first engaged, it caused the pedal to start sinking to the floor after. Then, it engaged again and suddenly the pedal was no longer sinking when being pressed again. It seems to be heavily related to the ABS engaging.
I'm not sure what to do now, as it very frustrating to have a sinking brake pedal, even after replacing the master cylinder essentially twice. I've read that the ABS System lines also need to be purged, but you have to have the Techstream software to do so. Which means that I would have to go to the dealership in order to do that, which would probably cost a lot of money, or get a Techstream cable/ adapter and use that. Does anyone have any experience with this? How much would a dealership typically charge to do the bleeding, can I even go to the dealership and tell them that I only want the brake lines/ABS system to be purged? (I've never been to a dealer for service, so I'm not sure if that's something that is possible).
If I don't go to the dealership, and I bought a Techstream cable/adapter and got the software, would I need to open up any brake lines for the ABS to allow the air out, or do I simply run the ABS bleeding utility and let the software do all the work?
Or is it even possible that it has nothing to do with the ABS System? Thanks in advance for any help!
01-20-19, 11:23 PM
#2
Intermediate
It doesn’t sound like the mechanic knows how to bleed Lexus brakes properly.
Go to this thread and and scroll down to Post #22 for a beginner’s thumbnail sketch on the proper way to accomplish this task. I feel sure some others here will be along shortly to help with more info, but I know that from your post the mechanic did it wrong.
Stay with us.
Read more here: https://www.clublexus.com/forums/gs-...er-99-a-2.html Post #22.
01-21-19, 05:07 AM
#3
It doesn’t sound like the mechanic knows how to bleed Lexus brakes properly.
It does not sound like, after the first time the system was cracked open, it was bled properly. Following that link would be the first thing to try.
If you actually had seized front calipers, before I did that bleed, I would get rebuild (seal) kits for the rear. Pop the pistons out, polish the bores and put in new seals. Then do the proper bleed procedure. If the car had that much water in the system long enough to pit the front bores, the backs can't be looking good, either. Fix them now and avoid repeating the hassle again soon. The rebuild kits are cheap and it's not hard to do.
Some auto parts stores loan cylinder hones if you need one, or they are not expensive. It's better than using crocus cloth or sandpaper, but those can work, too. This is all there is to "rebuilt" brake calipers so it makes sense to do it yourself for $5 a caliper.
01-21-19, 04:21 PM
#4
Lexus Test Driver
You dont need a techstream to bleed the actuator.(If yours is equipped with VSC)
If your actuator has a bleeder screw, just bleed it like a regular caliper.
I wouldnt pump it though.
I'd have someone step firmly on the brake pedal.
Then crack the actuator bleeder. (Key off so the actuator motor doesnt run)
If your actuator has a bleeder screw, just bleed it like a regular caliper.
I wouldnt pump it though.
I'd have someone step firmly on the brake pedal.
Then crack the actuator bleeder. (Key off so the actuator motor doesnt run)
01-23-19, 01:59 PM
#5
Pit Crew
Thread Starter
It doesn’t sound like the mechanic knows how to bleed Lexus brakes properly.
Go to this thread and and scroll down to Post #22 for a beginner’s thumbnail sketch on the proper way to accomplish this task. I feel sure some others here will be along shortly to help with more info, but I know that from your post the mechanic did it wrong.
Stay with us.
Read more here: https://www.clublexus.com/forums/gs-...er-99-a-2.html Post #22.
+1.
It does not sound like, after the first time the system was cracked open, it was bled properly. Following that link would be the first thing to try.
If you actually had seized front calipers, before I did that bleed, I would get rebuild (seal) kits for the rear. Pop the pistons out, polish the bores and put in new seals. Then do the proper bleed procedure. If the car had that much water in the system long enough to pit the front bores, the backs can't be looking good, either. Fix them now and avoid repeating the hassle again soon. The rebuild kits are cheap and it's not hard to do.
Some auto parts stores loan cylinder hones if you need one, or they are not expensive. It's better than using crocus cloth or sandpaper, but those can work, too. This is all there is to "rebuilt" brake calipers so it makes sense to do it yourself for $5 a caliper.
It does not sound like, after the first time the system was cracked open, it was bled properly. Following that link would be the first thing to try.
If you actually had seized front calipers, before I did that bleed, I would get rebuild (seal) kits for the rear. Pop the pistons out, polish the bores and put in new seals. Then do the proper bleed procedure. If the car had that much water in the system long enough to pit the front bores, the backs can't be looking good, either. Fix them now and avoid repeating the hassle again soon. The rebuild kits are cheap and it's not hard to do.
Some auto parts stores loan cylinder hones if you need one, or they are not expensive. It's better than using crocus cloth or sandpaper, but those can work, too. This is all there is to "rebuilt" brake calipers so it makes sense to do it yourself for $5 a caliper.
You dont need a techstream to bleed the actuator.(If yours is equipped with VSC)
If your actuator has a bleeder screw, just bleed it like a regular caliper.
I wouldnt pump it though.
I'd have someone step firmly on the brake pedal.
Then crack the actuator bleeder. (Key off so the actuator motor doesnt run)
If your actuator has a bleeder screw, just bleed it like a regular caliper.
I wouldnt pump it though.
I'd have someone step firmly on the brake pedal.
Then crack the actuator bleeder. (Key off so the actuator motor doesnt run)
08-27-22, 06:17 PM
#6
If the front calipers had seized air may be coming back through them when no pressure or maybe a slight vacuum is on the system. Because of slight rust the bores not being perfectly smooth. Because it sounds like after the bleeding it's good to go. But then not too long after the same issue returns. Seals are made for different applications. I high pressure seal isn't the same as a vacuum seal. And I've seen this exact same issue on a old civic I used to have way back when. Took me forever to figure it out. But that car had a normal master cylinder. Our ls460s dont use the same tech. All braking is controlled and comes from the abs module. Might be worth looking in to.
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