J reg. 405 no brakes sometimes when emergancy braking.HELP

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Dazzer
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J reg. 405 no brakes sometimes when emergancy braking.HELP

Post by Dazzer »

My girlfriend has a 405 turbo diesel. Its got ABS. Has had an intermittent problem with the brakes - when slamming them on in an emergency sometimes very little happens!!! Slightly alarming...... occurred very rarely, kind of felt like the servo had run out of vacuum

This happened once or twice and I checked the servo for correct operation a few times and it appeared OK. (engine off depressing pedal gives a progressively higher pedal, foot on pedal start car pedal sinks, after a couple of mins turn off and pedal gets higher after each press)

It now appears to be happening more often. And now it is a clicking as if the ABS is working?

I've flashed the codes from the ABS ECU and got -

41 wheel speed sensor left front signal
57 electronic control unit supply voltage

She had a look at the speed sensor ring 'teeth' on the near side drive shaft, they were a bit muddy but cleaned up OK and showed no damage.

Today she tried to check the codes again but could not get any response from the ECU (earthing the diagnostic socket for three seconds after key on).

Anyone got any ideas / suggestions? How do you test the vacuum pump for correct operation?

I've not had a lot to do with ABS previously. I will check the supply voltage to the ECU and then the front sensor(s) for correct function (I guess this is a UK nearside faulty sensor?) using a multimeter. I also have a data logger that is fast enough to use as an oscilloscope to catch the AC voltage coming from sensor when I spin it.

Is there a/some common fault(s) that could cause this? I would not be surprised if there was more than one fault as the symptoms appear to have changed.

Best

Dazzer
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matt
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Post by matt »

Cant help you with the electrical side of things but i had a servo failure on a previous 405 but you could tell something was wrong under normal conditions not just emergency braking,ie the brakes were crap all the time!!

i changed the vac first but it wasnt that,its only a mild suction by the way nothing major really.All i did was pull the pipe of and feel for suction when the engine was running.
By the sound of your description i dont think its the vac pump

I think you may find that the electrics are temperamental at the best of times- mine blows abs fuses regular but i just change them for mot time!

Good luck
92 205 1.9 GTI(MODIFIED,SORRY )
1996 VOLVO 850 2.5 5CYL 10V
1999 EXPERT VAN TD - WHITE !
No more car's thanks!
Dazzer
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Joined: 09 Jan 2008, 14:23
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Post by Dazzer »

Looks like I'll be going through the electrics then.

I guess a brake fluid change would not go amiss either - anyone know if vapour / air in the system could cause this ?(failure only under hard/sudden braking)
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