Well after reading this thread I tried bleeding the brakes and the noise went away. However since it started getting cooler in the mornings the noise slowly came back. This morning the noise was back with pumping and grinding noises and then the ABS light and alarm sounded. Guess mine is finally toast.
Booster Pump / Accumulator Noise diagnosis
- Thread starter Scottb4857
- Start date
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I have now replaced everything possible on my brake system...I still have the same noise! Any ideas?
fooldall1
Handy Enthusiast
At this point, take it to the dealer or a mechanic- at least to give you some idea before you drop another dime.
2001LC
SILVER Star
There is and adjustment to center the accumulator boost tank. If off center it can make sounds as vibration gets transfer to housing. If no warning lights and brakes working good, I look at the adjustments
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Thanks for the advice, I'll see if I can find that adjustment. Do you think it could cause the noise like what I posted? I also think I might replace the silencer tube and o-ring on the accumulator while I'm working on it.
2001LC
SILVER Star
Yes I do think that may be sound!
You did this correct: Pump pedal 40 times with key off and check level. Then turn on key and time how long booster pump runs. It should run between 30 & 40 seconds then stop. If not bleed brakes and try again.
If sound doesn't stop after adjusting and or Run time test var's over 40 second. Then you've and issues that need attention ASAP, driving is not recommended. If alarm comes on do not drive.
You did this correct: Pump pedal 40 times with key off and check level. Then turn on key and time how long booster pump runs. It should run between 30 & 40 seconds then stop. If not bleed brakes and try again.
If sound doesn't stop after adjusting and or Run time test var's over 40 second. Then you've and issues that need attention ASAP, driving is not recommended. If alarm comes on do not drive.
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2001lc I had that squeeling sound this morning for about 1 minute first time no warning lights brakes are fine.Have you got any diagrams of the adjustment to perform ?.Thank you
2001LC
SILVER Star
Found if I just grab it and pull away from side it touches, that often works. If you need to loosen bolt, seem to be one on underside. If that doesn't work come back and let me know.
Make sure you've good fluid and to proper level.
Make sure you've good fluid and to proper level.
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2001LC
SILVER Star
Thanks for your help. Are you talking about adjustment of the brake booster accumulator with yellow stickers on firewall adjusting it moving it a bit from firewall.My brake fluid was changed last year and blend to.
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2001LC
SILVER Star
Yes the accumulator (yellow sticker on it). But not away from firewall. The diagram in post #27 above shows the bracket looping around it. Sometimes the accumulator rides on a cushion in that bracket, which it should not. FSM gives us a gap (post #27) The No 1 bracket (see post #30) has a bolt holding it onto accumulator pump housing with sleeve, collar, cushion and washer. Bracket pivots on bolt.
Hi there I did as you told me fiddling with with it from the side made no difference.Last 3 days cold start only I have been getting that screeching sound no warning lights tho.Why does it happen only at first starts ?.Any other suggestions any help much appreciated.
2001LC
SILVER Star
It may be brake booster motor, pump and or accumulator is current thinking. It may be a pulley (idler or tensioner) bearing at front of engine. You'll need to isolate when cold.
If booster component(s) it will need replacing or rebuilding.
If booster component(s) it will need replacing or rebuilding.
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Was it ever solved? Same sound here, intermittent with warning lights and alarm .
My motor was checked by a shop and good.
Pump and accumulator are sold separately.
I know that the proper thing to do is replace it all, but I would rather fix the problem.
My motor was checked by a shop and good.
Pump and accumulator are sold separately.
I know that the proper thing to do is replace it all, but I would rather fix the problem.
I've been dealing with this issue myself; I've been able to draw a few conclusions, I've had the pump replaced twice now (both rebuilt units) as well as a brand new accumulator - If you put your finger on the red line that connects the pump and the accumulator on the bottom side of the assembly, you can feel some pretty gnarly vibrations.
The first replacement pump was replaced and good for about 1000 miles, and the sound came back. Again, I replaced the motor under warranty and it was good for 1000 miles and the sound came back - only now it is intermittent and it gets to a point where it makes the sound but if i shut the vehicle off for 20 seconds and restart the sound goes away and I can go about my day.
I believe it does indeed have something to do with air in the system.
The first replacement pump was replaced and good for about 1000 miles, and the sound came back. Again, I replaced the motor under warranty and it was good for 1000 miles and the sound came back - only now it is intermittent and it gets to a point where it makes the sound but if i shut the vehicle off for 20 seconds and restart the sound goes away and I can go about my day.
I believe it does indeed have something to do with air in the system.
2001LC
SILVER Star
I wondering if your terms of parts replace are correct. I've not heard of booster pump being rebuild. Motors are! You also said brand new accumulator. That is the cylinder that attaches to pump. In diagram above we see "booster pump motor" it is actually both the motor and pump shown together. Then Accumulator shown separated with with O-ring Spring and Silencer tube going between them.
So looking at post #30 above, can you list which parts were replaced (motor, pump, accumulator). Please also including if O-ring Spring and Silencer tube?
My apologies, for the sake of my post, pump/motor refers to the small black cylindrical motor, "booster pump motor" on the bottom of the pump. When I mention the accumulator, it's as it's labeled in the diagram. The o-ring and silencer tube were not replaced.
Still having issues. I just rebuilt the master cylinder. Brakes work fine. If I bleed the system, it’s perfect for a few days. Then the noise and alarm return. I believe a possibility is the o’ring, spring, and silencer tube between the pump and accumulator.
I’m calling my local dealership to see if they stock them seperate.
I’m calling my local dealership to see if they stock them seperate.
