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Break bleed with ABS assisted system


sira
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Dear Friends

I recently brought Demio 2001 car and it got ABS break system. Today i replaced break liners and just checked any air on the system because it looks never touched for a long time. so when i bleed rear left wheel . after few second time there was no any break oil in the line. so i checked total system and notice , there was block on output line on the ABS module. then i start the engine and run the car and applied hard break . hear the ABS spinning sound too. then noticed that the block lie now cleared and when i press the break paddle it squirt break oil.

will there be a block on ABS line ?

is there any other way of bleeding ABS assisted breaking system?

do we need to service ABS system with specific time period

Thanks

sira 

 

  

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So was the block within the ABS modulator itself or in one of the output lines from the modulator? 

As for your question about bleeding ABS systems, there isn't anything special about the bleeding procedure itself. But before any brake repair, it is advised to use a brake pedal depressor (or some other method) to fully press the brake pedal until the repair is done. This is done to prevent air from entering the system through the master cylinder and subsequently entering the ABS modulator. On some ABS modulators, there is a special bleeder nipple that you can use to bleed the modulator itself.

About the service requirement for ABS systems, there really isn't anything special that needs to be done from a conventional brake system. The ABS system will light up the ABS indicator if something is wrong. 

Edited by Davy
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2 hours ago, Davy said:

So was the block within the ABS modulator itself or in one of the output lines from the modulator? 

As for your question about bleeding ABS systems, there isn't anything special about the bleeding procedure itself. But before any brake repair, it is advised to use a brake pedal depressor (or some other method) to fully press the brake pedal until the repair is done. This is done to prevent air from entering the system through the master cylinder and subsequently entering the ABS modulator. On some ABS modulators, there is a special bleeder nipple that you can use to bleed the modulator itself.

About the service requirement for ABS systems, there really isn't anything special that needs to be done from a conventional brake system. The ABS system will light up the ABS indicator if something is wrong. 

Hi Davy

Thank you for the update. I just unscrew particuler pipe on the ABS module. have't got a clue weather it is module or pump. is there any way for isolate it.  I was not used ABS car for last 15 years time and now only getting experience with this. same like ABS and AT gear box.

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2 hours ago, sira said:

Hi Davy

Thank you for the update. I just unscrew particuler pipe on the ABS module. have't got a clue weather it is module or pump. is there any way for isolate it.  I was not used ABS car for last 15 years time and now only getting experience with this. same like ABS and AT gear box.

Modulator/Pump - they all refer to the same thing. It's the unit where the output line from the master cylinder go into and then 4 output lines come out of, one for each wheel. Something like this:


abs_unit.jpg

I hope you removing the line from the ABS module didn't cause air to get into it, because if it did, then you might have to bleed the ABS modulator separately.

Anyway, the block might have been in the ABS modulator itself as a result of a piston being stuck or something. Your brake test might have caused the the motor in the modulator to be activated and clear off the block. Just an assumption. I'd suggest reassembling everything, bleeding the entire system (starting from the wheel that is furthest to the master pump and moving to the next furthest one and so on until you bleed all four wheels).

If you have an uninterrupted supply of brake fluid reaching all wheels, then you should be fine. Check if your ABS still operates normally and keep an eye on the affected wheel after the repair.

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@sira the way you are trying to do this is a bit scary. Make sure you do not have air trapped in the pipes and the modulator. If it was an output line from the top of the unit that you removed then it is unlikely to result in air bubbles in the modulator unless you pressed the pedal and partially emptied the fluid in the module. However whenever I bleed a brake system I prefer to compress all four slave cylinders with a G-clamp to pump old fluid back to the reservoir and then remove the fluid in reservoir with a syringe. Then I re-assemble the whole brake system before starting the bleeding process explained by Davy above. This way you leave a minimum of old fluid in the system although it involves bit more work unless done along with a pad change or a cylinder repair.  

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Hi Davy

I just bleed the all wheels. rear L , Front R ,Rear R and Front L. when i bleed them i let oil go alot. because earlier there was block. looks ok no block of any pipes or ABS module. 

The difference i noticed this car is when i press the paddle very hard, car dose not like to  stop. my Ek3 (non ABS) it;s stopps with hard break (20-30 KMPH) and over 70-80 wheels locks.

This car  around 20 -30 kmPH, smooth break can apply and it reduces the speed but if i keep pressing the paddle hard . it's lazy to stop.. Will the ABS activated  20-30 too? or any other issue

thanks

sira

 

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6 hours ago, sira said:

Hi Davy

I just bleed the all wheels. rear L , Front R ,Rear R and Front L. when i bleed them i let oil go alot. because earlier there was block. looks ok no block of any pipes or ABS module. 

The difference i noticed this car is when i press the paddle very hard, car dose not like to  stop. my Ek3 (non ABS) it;s stopps with hard break (20-30 KMPH) and over 70-80 wheels locks.

This car  around 20 -30 kmPH, smooth break can apply and it reduces the speed but if i keep pressing the paddle hard . it's lazy to stop.. Will the ABS activated  20-30 too? or any other issue

thanks

sira

 

Glad to hear that you managed to bleed the system fully. 

ABS activation happens at any speed when you apply brakes and if that causes the wheels to lock up. For someone used to driving cars without ABS on which wheels lock up under heavy braking, this might seem like braking power is less, but that is normal and it happens because the car doesn't let the wheels lock up to prevent skidding.

When you say that the car doesn't like to stop at low speeds under heavy braking, do you feel ABS kicking in (pulsating pedal)?

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Just to add a line to what Davy already said, if you find ABS activating at slow speeds it could be due to one or more wheel sensor failing to detect wheel rotation thus mimicking a wheel lock up condition. A DIY method to check this is to drive at around 10kmph constant speed without applying brakes for about 500m and see if you get an ABS fault code. You can trace to the particular sensor by reading the fault code. You can clean the sensor if it is a front one but may have to replace if it is rear.

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