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2004 RT ABS noise


Mamelukesword

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Mamelukesword

I searched for some ABS stuff and couldn't find anything like I am experiencing, so I am asking for some help. I just bought my RT it has 36k miles on it. When started the Brake light flashes correctly until I start going then goes out. No other fault lights. The ABS "whining" never stops regardless if the brakes are depressed or not. Is this normal?

 

Thanks

Dennis

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The light is normal, but I don't think you should be hearing any ABS noise when you are not depressing the brakes. I'm sure more experienced members will chime in soon.

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If by "whining" you mean the brake servo motor is always running, then no it is not normal.

Check the micro switches adjacent to the lever/pedal.

The rear brake pedal/switch is notorious for picking up debris.

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Hi Dennis welcome to the group.

Jeepster has the most likely cause.

This is a fairly common cause and so just take a gaze up the right hand footrest plate and you will see the 'leaf' that actually operates the micro switch. With engine and ignition off, gently operate the rear brake pedal and listen for the micro switch to 'click', it probably won't, becuase it is already actuated.

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Dennis, here is a shot of the microswitch with it's leaf, from the inside (so you know why debris can cause a jam).

 

I'd check the front brake lever 'clicks' too. Also check your brake lights are working correctly. The tail light takes over from the brake light if it's filament goes.

 

Andy

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Afternoon Denis

 

Are you sure it’s the ABS whirring? As a rule on the BMW IABS systems the warning light won’t go out at roll-off IF either brake light switch is open.

 

Listen carefully with the gas cap opened up to be sure you aren’t hearing the fuel pump running. Some BMW fuel pumps can be about as noisy as the ABS pump.

 

 

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Mamelukesword

Did some troubleshooting, it is the front brake micro switch, there is some play in the front brake lever. Is there any adjustment to the front lever to ensure it isn't engaging the ABS?

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Hi Mamelukesword,

The lever is normally pushed back out due to the piston return spring acting against the 'blow by' adjusting grub screw in the side of the lever.

Does the lever spring outwards again after applying the front brake?

If your piston is returning correctly, then it seems as though the lever pivot is that worn so it is actuating the microswitch just because of it's own weight.

 

1/. You could pop the lever off and refit it. The pivot bolt may be worn (or the pivot hole), so by putting the bolt at a slightly different position may reduce the play a little (remember to put a tiny dod of blue loctite on the bolt threads).

2/. Get hold of a replacement lever and bolt.

3/. Ensure the microswitch leaf is correctly positioned.

4/. maybe you could tweek the microswitch leaf so that it requires a little more lever movement?

If it is a badly worn pivot, I'd opt for choice 2/.

 

Andy

 

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Mamelukesword

Thanks Andy, for now I adjusted the leaf slightly (temporary fix). My grub screw does not turn at all, so I think a new lever is needed. I am going to research some new parts and hopefully that fixes the problem.

 

Dennis

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Morning Dennis

 

That grub screw is usually has Lock-Tite from the factory. Try removing the lever then heating the screw area, that will soften the Lock-Tite enough to allow it to be moved.

 

In any case be careful when adjusting that screw as the master cylinder piston MUST ALWAYS return all the way out to contact the snap ring or the fluid take up port hole in the cylinder bore will be blocked by the piston so won’t allow the fluid pressure in the cylinder to fully release at lever release (causes dragging brakes). Also, if the piston doesn’t fully return out then new fluid can’t enter the bore in front of the piston.

 

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Mamelukesword

Ok, that is good information DR. I have a manual, I am going to ensure the amount play is within limits. Not sure, but I think the switch may just be old too and may need replaced. I don't have a local dealer so I will be ordering parts online.

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I don't think adjusting that 'blow-by' grub screw is going to help you fix this problem (DR is correct the grub screw is loctited so that after the 'blow-by' has been set up correctly, it doesn't drift out of adjustment and cause your brakes to drag.

 

The Servo is switched on by the microswitch not by movement of the cylinder piston.

You say the switch "may just be old too and may need to be replaced". I would say once you have the lever off, check the microswitch works reliably and then just aim for the lever & pivot bolt.Normally these switches are very reliable and it is only muck & debris that interfere with there usual sweet running.

Andy

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