racoguy

Hi everyone, first time Porsche owner and loving the experience so far but having continued PDAS / ABS / Brake press light issues on my 90 C4 done lots of reading and testing but have not found much info on the accumulator and how to test it.
So far have cleaned accelerometers, tested abs sensors (range 1002-1008 ohms) cleaned earth points for abs sensors
Found I was loosing fluid and one of the locks was leaking so re kitted both with kits from 9Meister and now holds fluid.
(have not driven car since but brake pressure light stays on once started)

Scanned tonight with Durametric and no faults logged (battery has been off)
With the system at full pressure Pump runs for 30 sec ish and turns off, I get 2 pumps of the pedal and on the 3rd pump the booster pump starts again and runs for maybe 5 seconds, once stopped it starts again on the 3rd pump. (all with key on)
With the key off and system charged it takes 30 odd pumps before the pedal goes rock hard.

racoguy

Anyone at all?
Am I missing a component here, seems to be a plug that goes nowhere?

jlmartin94

seem to have the same behavior on my 1991 C4 .
but still want to replace the accumulator as i think that after 20 year of duty , he should go in the trash can
maybe the pump itself is a little lazy and take too long to build the pressure ?

for your light , if she stay on after startup ( and after more thant 60sec ) you should have a fluid "level" problem .. ( contactor on top of dot reservoir .)
not a "pressure" problem because the pressure warling come with the HORN !!

no idea fore the plug .

racoguy

Had the car scanned today and had this fault
44 fault cond 18 front rear diff lock deviations code 18
Both lock cylinders have been re kitted, any ideas where to look next?
Can someone also check if the pictured plug goes anywhere on their C4 please?
Not really sure where to look next.

Mixter

Here's a pic from my car. I have the same plug that goes nowhere.

jlmartin94

did you bleed the whole system ?
i had bubbles in the two valves diff lock and i had some strange behaviour .
PDAS/ABS error light goes on ( with warning gong ) on startup ( while the built In test Equipement ) .
that would explain your fault code too ..?

racoguy

Yes I bled the whole system and both locks several times, the pdas light comes on after driving over about 50kmh soon followed by the abs lamp.
Codes were cleared before the drive so were logged when the light came on.
Don't really know where to look next as I don't really know what the fault code means / relates to, I know obviously it's to do with the traction control but what's causing the fault.

Laurence Gibbs

The accumulator is pressure tested with a gauge. There is a procedure in the factory manual, basically you test for certain pressures at different parts of the cycle. I.e. max pressure, pressure over time after switch off and pressure switching levels for when the pump comes on. I am sure i have read somewhere that suggests that 3 pumps of the pedal would be enough for the pump to start running, So normal. Pressure warning obviously not normal. Have you checked around pressure switch to ensure that is not leaking ?

Laurence Gibbs

According to Adrian's book
Dynamic component problem:
check wheel sensors
test diff locks ??

racoguy

Pressure switch seems fine, no leaks and system holds same level over night.
Doing a google search on fault code 44 comes back with resonance plate??
Hardly any information I can find about it.
Currently only getting the traction light on followed by the abs light.

jlmartin94

maybe ( just an idea .. ) the "deviation" word refer to a bad signal comming from the 4 ABS sensor ( bolted on each wheel axel )

did you try to clean the 4 sensor ( cost nothing ... )

racoguy

Yes I cleaned all sensors and did an ohm test on each one and all are 1002-1008 ohm.
Did the test at each sensor but don't have abs plug pin out to do it at the abs plug.
Fault code 44 makes reference to front / rear diff lock though so would assume its to do with that?

Turbohead

I have the whole unit if you need it
Elliot