ABS Pump Screeching (2 Viewers)

[Quatrek]

Hello,
I'm a new owner of a 2003 GX470 and have a couple questions concerning the ABS pump. My ABS pump was operating fine until about a week ago when a started hearing a screeching/ grinding sound occasionally on one if not two of the booster intervals. But more recently (a couple days ago) the booster intervals have been all screeches without fail. It's not the whining sound that I have hear in other videos and only happens when the booster kicks in. I've tries flushing the system and bleeding in the correct sequence but no luck... the sound continues. Can anyone tell me what this is? Or how I can diagnose it? I like working on my own rigs but this is stumping me.
Here are a couple videos with audio of the issue.
GX 470 - https://photos.app.goo.gl/kDHoPFqsqxpsTJ5W8

 

[Jstawgn]

Pretty common failure. At one point it would fail to generate pressure and you would have no brakes.
Andy Le out of Rancho Cordova, CA do good job rebuilding this hydraulic master cylinder/brake booster/VSA/TRAC module

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[Quatrek]

Would it be worth it to replace the whole unit rather than rebuilding it?

 

[Zjohnsonua]

That screeching could be the result of a few things. Most of which would have been addressed by a fluid flush which you have already done. There's a high pressure relief valve in the master's hydraulics circuit that will make that noise as fluid passes through it when either the valve or the high pressure switch fails. Neither of which are serviceable. The fix in that case is to replace the unit.

The master cyl rebuild that was mentioned replaces the piston and associated o-rings and it seems to mostly fix a soft or dragging pedal. How does your pedal feel when driving?

 

[Quatrek]

That screeching could be the result of a few things. Most of which would have been addressed by a fluid flush which you have already done. There's a high pressure relief valve in the master's hydraulics circuit that will make that noise as fluid passes through it when either the valve or the high pressure switch fails. Neither of which are serviceable. The fix in that case is to replace the unit.

The master cyl rebuild that was mentioned replaces the piston and associated o-rings and it seems to mostly fix a soft or dragging pedal. How does your pedal feel when driving?

The pedal feels fine and responsive, that’s the only reason I’m still driving it. Also posted this to a Reddit thread and someone said that they had the same noise and that the booster motor needed to be replaced. I would much prefer just buying the motor and installing it myself but don’t want to waste money. What do you guys think?

 

[Zjohnsonua]

You're not gonna like this answer but it's what I can offer. Check around and see if you can get the master sans pump/motor. If you can, try the pump/motor, and if that doesn't fix you you'll be looking at the master. At least at that point you'll have a new pump to make a new assembly.

This assembly is definitely not as straightforward to troubleshoot as a traditional system.

 

[Quatrek]

You're not gonna like this answer but it's what I can offer. Check around and see if you can get the master sans pump/motor. If you can, try the pump/motor, and if that doesn't fix you you'll be looking at the master. At least at that point you'll have a new pump to make a new assembly.

This assembly is definitely not as straightforward to troubleshoot as a traditional system.

No that’s great! Thanks for your help! Really appreciate it!

 

[Quatrek]

So I've replaced the booster motor but the sound is still there. I have however noticed some more oddities to this problem. First off, the sound is much quieter in the morning... probably due to the engine not being warm. Could this be important in the diagnosis of this issue? The first drive of the day is around 5 miles usually, and the sound is faint but still present. Once I go home for lunch, the sound is much louder, like in the video above. The abs system seems to be holding pressure so I don't think the accumulator is a part of the problem, but I could be very wrong. Is there anything I could look into before dropping the money on a master?

 

[VongGX470]

So I've replaced the booster motor but the sound is still there. I have however noticed some more oddities to this problem. First off, the sound is much quieter in the morning... probably due to the engine not being warm. Could this be important in the diagnosis of this issue? The first drive of the day is around 5 miles usually, and the sound is faint but still present. Once I go home for lunch, the sound is much louder, like in the video above. The abs system seems to be holding pressure so I don't think the accumulator is a part of the problem, but I could be very wrong. Is there anything I could look into before dropping the money on a master?

I just went through the same issue and replaced both the hydraulic brake booster motor and the accumulator. The screeching noise is due to the accumulator failure. Now you need to replace the accumulator. Sorry, you will have to pull the whole unit out again to work on the accumulator unit. That fixed the noise for me. Good luck.

 

[Quatrek]

I just went through the same issue and replaced both the hydraulic brake booster motor and the accumulator. The screeching noise is due to the accumulator failure. Now you need to replace the accumulator. Sorry, you will have to pull the whole unit out again to work on the accumulator unit. That fixed the noise for me. Good luck.

Thanks for the info! Did you have a similar sound coming form the accumulator? I was poking around the abs system and was feeling for the intervals and noticed the vibration of the accumulator was synced to the noise haha. Did you change out the piece connecting the booster pump and accumulator or just replace them separately? I have a solid lead on an accumulator but not the housing that attaches them together. Having replaced the booster motor I would like to keep it and not purchase the set.

 

[VongGX470]

Thanks for the info! Did you have a similar sound coming form the accumulator? I was poking around the abs system and was feeling for the intervals and noticed the vibration of the accumulator was synced to the noise haha. Did you change out the piece connecting the booster pump and accumulator or just replace them separately? I have a solid lead on an accumulator but not the housing that attaches them together. Having replaced the booster motor I would like to keep it and not purchase the set.

I just replaced the 2 units - not the OEM housing that holds them together. To remove the accumulator, you need a tool that fits on the 2 notches on the top to remove it and put the new one on. Torque to 40 ft-lb

 

[Live to Ski]

Does anyone have Andy Le's contact info?

I've scoured ebay but can't find it

 

[DawnpatrolCBNC]

Does anyone have Andy Le's contact info?

I've scoured ebay but can't find it

I don't know if you still need it, but I sent you a PM.....

 

[bcomnes]

I think I have the same issue. Did it sound like this?

 

[bcomnes]

Sorry here is the video

 

[bcomnes]

Anyone have a Pn on the accumulator?

 

[bcomnes]

Looks like maybe the accumulator is part: 47950-30010

Would you be able to confirm if that is correct @VongGX470 ? Does the sound in that video match what you remember? Did you need to replace anything else besides the accumulator?

 

[GXO]

I have done a bench rebuild of a master with a new motor and accumulator on a 100 series and a full swap on my 470. The failure mode is always the motor, accumulator, the wire from the motor to the solenoid, and then the solenoid (ABS controller). In that order. So if you do rebuild, I would suggest getting the motor, accumulator, and wire and clean up everything. The ABS controller and whole assembly is where the money train starts to leave the station.

 

[drowzyGX]

Might be a stupid question, but does this just go with time / miles on the GX? Something worth adding some extra funds to the “car emergency” account? I do mostly city driving. I know the stop and go adds a lot of wear and tear.

 

[bcomnes]

I have done a bench rebuild of a master with a new motor and accumulator on a 100 series and a full swap on my 470. The failure mode is always the motor, accumulator, the wire from the motor to the solenoid, and then the solenoid (ABS controller). In that order. So if you do rebuild, I would suggest getting the motor, accumulator, and wire and clean up everything. The ABS controller and whole assembly is where the money train starts to leave the station.

Looks like they sell an assembly with the motor and the accumulator and wire for almost the same price as just the motor.

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