Pulsing brakes

[chezz]

ABS, not the discs, not the servo...don't confuse the man by sending him off on a wild goose chase lads

[willg54]

nope, not speed related i dont think. the discs are spot on, rears are new and fronts are skimmed and are within a couple of thou.

i have the fault for front left ABS sensor and abs light is on so i'll aim to get rid of that first and see what happens.

[willg54]

no change with removing the ABS fuse. It wasn't working earlier anyway, left 2 big 11's down the driveway when i did a really hard brake.

going to do a big bleed again now and also check the sensors.

to check the resistance, what wires to I want to be testing and what values should there be?

[mcandmar]

In my experience issues with pump/bomb/servo are at there worst when cold, usually when you first start the car the pedal pulses away until you have done a few miles. It can be a case where it only happens if the car sits for a few days, but with daily use it dosent happen. Rather than spending real money the first thing i do is flush the fluid, and remove all the banjo bolts from the pump and clean them out as most have a fine gauze filter in them. If the servo is badly worn and wont let the bomb build up pressure try holding the brakes on for a minute or so.

ABS pulsing is a much more severe, you will also hear the ABS unit run at the same time so its easy to tell them apart.

[willg54]

In my experience issues with pump/bomb/servo are at there worst when cold, usually when you first start the car the pedal pulses away until you have done a few miles. It can be a case where it only happens if the car sits for a few days, but with daily use it dosent happen. Rather than spending real money the first thing i do is flush the fluid, and remove all the banjo bolts from the pump and clean them out as most have a fine gauze filter in them. If the servo is badly worn and wont let the bomb build up pressure try holding the brakes on for a minute or so.

ABS pulsing is a much more severe, you will also hear the ABS unit run at the same time so its easy to tell them apart.

Thanks

It certainly isn't the ABS kicking in. I've just been around and tested all the sensors and done a full bleed.

About to go and try it again. if that's no luck, i'll try pulling the hose to the bomb off and see if there's anything coming out of it.

If that's all ok, i'll go and check the banjo bolts as you suggested

[willg54]

i think it's sorted.

The front left sensor which had the error code didnt seem quite far enough in and the resistance response was rubbish, adjusted that and tried again.

I now have full abs working and no pulsing feel from the pedal hopefully that will be ok for the MOT and i can give it a good drive after

[willg54]

right, i still have the brake problem...

pulsing pedal and really jerky brakes.

Bomb test says it's ok
ABS is working

So I'm thinking its the Servo. Which is the hydraulic return from the servo? I can see where it's bolted to the bulkhead and mastercylinder but can only see one line going to it.

I took the hydraulic line off from the Bomb too and only a small dribble of fluid came out of that...is that correct?

[willg54]

Been looking at it and I reckon its the line on the top next to the bulkhead? Correct?

How are you supposed to take that off? Sod all access!

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[newsh]

Have you done the full lock to lock a few times to bleed the PS system? Topped up the G004000?

[willg54]

I've driven it a fait bit and topped the fluid up. Would doing a full lock to lock still change things?

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[willg54]

Have you done the full lock to lock a few times to bleed the PS system? Topped up the G004000?

Just tried this, the fluid went down a little, topped it up but the problem's still there.

I'm thinking servo more and more.

it's got to be something hydraulic related, it brakes hard and and in a straight line but jerks with hard and soft braking power.

[chezz]

it's got to be something hydraulic related, it brakes hard and and in a straight line but jerks with hard and soft braking power.

Does the pedal feel like it is going very soft when you brake and is the ABS modulator going crazy? Lots of noise!

[nip]

Will when it was off the road did u strip the pistons and seals out of the calipers ?

[willg54]

Yup, front and rear.

Got built with new ones

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[willg54]

Defo not abs, that's all sorted. It's a slow pluse, about 0.5hz

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