LS - 3rd Gen (2001-2006) Discussion topics related to the flagship Lexus LS430

Brake Booster Troubleshooting

Old 06-28-18, 01:06 AM
  #16  
Mbodall
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Amateur opinion? My money is on the brake booster being bad.

Then again, what do I know? Could be a bad brake booster gasket? Could be your master cylinder or vacuum check valve? Check out these few images I grabbed from a free service manual: (They're from pages 58-61 of the service manual which can be found here. The subsequent pages talk about the master cylinder. I'd start following along in the manual and see what you can figure out)





Last edited by Mbodall; 06-28-18 at 01:09 AM.
Old 06-28-18, 01:26 AM
  #17  
SlkySmooth
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All of those tests seemed easy enough except for the check vacuum valve. I know there's enough vacuum going to the booster but how could I make sure there's none going to the engine. I'd removed it earlier and it seemed fine so I don't think it is the problem. Thanks for your feedback any other advice?
Old 06-28-18, 05:36 AM
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2KHarrier
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Well, for what it's worth, I have a hard time believing it's the booster that failed, rather it could be that check valve that has failed instead. You may just have vacuum running through the booster and not accomplishing anything due to a bad check valve. I would assume it works like a PCV valve, so if you gently remove it, it should be pretty evident if it works or not.


It's a fairly cheap part and looks to be easily replaced, so perhaps it's worth a shot to do that before diving into the booster itself..
Old 06-28-18, 05:53 AM
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I had pulled the check valve off and it didn't seem to be stuck or anything I was able to blow air threw it easily 🤷*♂️
Old 06-28-18, 05:56 AM
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Originally Posted by SlkySmooth
I had pulled the check valve off and it didn't seem to be stuck or anything I was able to blow air threw it easily 🤷*♂️
You should only be able to blow air through it one way. Blow, flip it around, - no blow..

Then you know the check valve is working.

If you can blow air through it from both ends, it's no good..
Old 06-28-18, 09:27 AM
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Originally Posted by 2KHarrier
You should only be able to blow air through it one way. Blow, flip it around, - no blow..

Then you know the check valve is working.

If you can blow air through it from both ends, it's no good..
It worked correctly like you described.

I guess I'll try doing a little more research on what's causing this issue

Does anyone know what causes the BRAKE light to stay on looking at the service manual it seems to point to issues with the skid control ecu
Old 06-29-18, 08:36 PM
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Threw the towel in this morning and had it towed to Lextechs of Atlanta in Johns Creek. They told me in the morning it'd be $50 to diagnose the issue and then whatever the fix costs. Got a call from them in the afternoon and they said they still had no idea what the issue would be and it'd cost me $330 after taxes for them to figure out the issue plus parts and labor for the fix
Old 06-30-18, 12:53 AM
  #23  
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Originally Posted by SlkySmooth
Threw the towel in this morning and had it towed to Lextechs of Atlanta in Johns Creek. They told me in the morning it'd be $50 to diagnose the issue and then whatever the fix costs. Got a call from them in the afternoon and they said they still had no idea what the issue would be and it'd cost me $330 after taxes for them to figure out the issue plus parts and labor for the fix
Wow! That $50 diag fee seemed very reasonable... so much for that At this point, it seems you've done everything else that you can do to try and diagnose it yourself, so it looks like you're just going to have to cough up the $$$
Old 06-30-18, 10:04 AM
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That sounds like bait and switch to me... ouch. I wouldn't go there again.
Old 06-30-18, 10:32 AM
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Yeah, that seems odd. 50 dollars to get in the door, and then charge me another 330 dollars when they can't figure it out.

It's doubtless too late at this point, but you may want to reconsider Lextechs...
Old 07-06-18, 07:24 PM
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Here's an update for those of you that were following my misadventure as well as anyone that might end up with the same issue in the future.

BRAKE light remaining on was a stuck floater in the brake fluid.

It turned out to be a an obstructed vacuum line rather than a leak. The paperwork said on the intake.

Weird thing is the vacuum gauge I got off Amazon has the same exact reading after having them clear the obstruction but the vacuum is so much stronger I can hear it with the hose off.

Paid for them to take care of the brake fluid while I was there and it made a huge difference from the sludge I was riding around with.

Out the door about $450 poorer but I believe I still saved more than having someone do all the work that got me in trouble in the first place so I'll live

They did a pretty detailed inspection with pictures so I've got a few things to tackle next like engine/transmission mounts.
Old 07-07-18, 02:48 AM
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Yay!! $450 ain’t too bad, really. It could have been much, much worse. Glad you finally got it worked out!
Old 07-07-18, 07:50 AM
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Originally Posted by Mbodall
$450 ain’t too bad, really. It could have been much, much worse.
Agreed.

Even me, the self proclaimed "I can fix anything" mechanic would be ok with spending that to fix the problem...

You're still money ahead by doing the other work yourself

I wonder if there was a piece of sealer stuck in the hose, or maybe a piece of gasket material?

Last edited by 2KHarrier; 07-07-18 at 08:40 AM.
Old 07-07-18, 10:46 AM
  #29  
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My best guess is that I didn't clean out the throttle body and it's many tiny holes well enough

Or maybe a spider got stuck in there lol
Old 07-08-18, 08:42 AM
  #30  
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Originally Posted by SlkySmooth
Or maybe a spider got stuck in there lol
This made me legitimately chucked out loud
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