2000 LX 470 Weird Brake Issue

Joined
Apr 8, 2021
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Hi Guys,

I have read a lot of the brakes out forums, but this problem I can seem to find.

Driving one day the abs light comes and I lose all brakes. I am able to navigate the situation without anyone being hurt. Get it back to its final resting spot. The mechanic comes 4 days later and says there are no lights on and the brakes work and look fine. I go out and drive it very gingerly at a low traffic time and everything is fine.

Thoughts?

Thanks in advance.
 
Joined
Feb 18, 2020
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Maybe a bad spot on the commutator of your brake booster motor, if it stops there it won't restart, but bumping and jostling around it may have moved just enough to get to a good spot and worked the next couple drives? I would at the very least be taking the motor apart and inspecting it closely, from everything I've read you've had your first warning. It will happen with increasing frequency and one of these times you'll likely be in a situation you can't get out of with no braking in a three ton truck.
 

JunkCrzr89

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That’s your first, and perhaps only, warning that your brakes are about to disappear entirely. I agree with @dbfw that inspecting the pump motor would be prudent.
 
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Ok,

I would like to add some background. Prior to the brake issue my mass air flow sensor had gone bad sending up all sorts of different codes/warnings on the dash. I had this fixed after the brake issue. Additionally, the LX has a lot of rust, but the wife got a car wash and we had below freezing temps that night. Is there any chance that this problem could be related. Or something electrical?

I did the pump the brakes 40 times and listen for buzzing . It buzzed every time for a pretty long time.

I am sorry. I just don't know what do . I am not mechanically inclined to pull the part off myself. Do I just "brake" down and buy a whole new unit and have it installed?

Anyone near NW IA that wants to make some cash and help me diagnose this?
 

JunkCrzr89

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had below freezing temps that night. Is there any chance that this problem could be related.
Partially, in the sense that the problem is often exacerbated and comes to light when temps are cold.

I did the pump the brakes 40 times and listen for buzzing . It buzzed every time for a pretty long time.
How long? The motor shouldn’t run more than 30 seconds after evacuating the accumulator.

I am sorry. I just don't know what do . I am not mechanically inclined to pull the part off myself. Do I just "brake" down and buy a whole new unit and have it installed?
No worries - we want to help. If you don’t want to go through all the troubleshooting steps to narrow down where the failure point is, then the easiest thing to do is buy a new unit. But that is also the most expensive route ($2300 for a new assembly), which, considering the rust you have, may not be the best use of your money.

I think in your case, finding someone locally (NOT A DEALERSHIP) who can help you pull the booster assembly for beer money is going to be the best case scenario. This would allow you to then a) have the pump motor rebuilt ($250-300), b) install a new pump motor and accumulator ($700), or c) buy a “rebuilt” booster assembly ($450-500), though I’m very skeptical that the guy who claims to rebuild the boosters actually does anything other than repair the pump motor and replace the reservoir grommets.
 
Joined
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Messages
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Location
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Maybe a bad spot on the commutator of your brake booster motor, if it stops there it won't restart, but bumping and jostling around it may have moved just enough to get to a good spot and worked the next couple drives? I would at the very least be taking the motor apart and inspecting it closely, from everything I've read you've had your first warning. It will happen with increasing frequency and one of these times you'll likely be in a situation you can't get out of with no braking in a three ton truck.
Ok,

So it was warm here and I am still screwing with the brakes. I had a hunch it might be something electrical. I opened the hood and started listening/feelin. I heard a constant two click deal coming from the fuse box. I felt the fuse that was doing it and was the ABS motor fuse. Big block fuse closes to the edge of LX. Will replacing this fuse fix or does this just indicate I have a wiring issue?

Thank you in advance.

I am sorry. As previously posted, my fix it knoweldge is extremely limited. I appreciate websites like this and people like you that have these skills/information. If you can believe it , I have J.D.. My brain works, but not when it comes to this stuff.

Thanks in advance.
 
Joined
Feb 18, 2020
Messages
145
Location
Tacoma
Ok,

So it was warm here and I am still screwing with the brakes. I had a hunch it might be something electrical. I opened the hood and started listening/feelin. I heard a constant two click deal coming from the fuse box. I felt the fuse that was doing it and was the ABS motor fuse. Big block fuse closes to the edge of LX. Will replacing this fuse fix or does this just indicate I have a wiring issue?

Thank you in advance.

I am sorry. As previously posted, my fix it knoweldge is extremely limited. I appreciate websites like this and people like you that have these skills/information. If you can believe it , I have J.D.. My brain works, but not when it comes to this stuff.

Thanks in advance.

I don't know the answer, but can say in all the brake threads I've seen here I don't think that has ever been the cause. Usually it has to do with the booster motor failing, or sealing issues internal to the master cylinder assembly itself so it won't hold full pressure. If you have a local cruiser specialist or another mud member nearby who can help you diagnose, I'd suggest that before continuing to guess.

When the brake issues inevitably pop up on these, it's painful to consider the cost to fix. But the consequences of guessing and getting it wrong are immense. About this time last year I started getting the "dying seagull" screech, meaning the master couldn't hold full booster pressure internally anymore. I had a long weekend trip planned with my wife that we cancelled, and I replaced the entire MC unit with new OEM. I didn't want to spend the money then, but was so relieved to have it done and know it was 100% fixed. Sudden brake failure in a 6,000 lb truck is a terrifying thought. Another consideration is the current parts supply situation. It looks like parts are beginning to be discontinued for these 100s, and the parts that are still in production may be out of stock. If you end up needing a booster or complete master assembly, there may not be that many available. If you find yourself with total brake failure and needing one immediately, you may be stuck waiting.

Ok, enough finger wagging...

Did you experience the clicking with the ignition on or off? There are known issues with the fuse box, but I believe it's usually the EFI relay that clicks or has connectivity issues as a result.

It might also be worth checking your front carpets to see if they're wet, moisture intrusion from clogged sunroof drains, bad windshield install, etc. has been known to cause horns to sound by themselves or relays to click until things are dry again.
 

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