Augusto

I am having some problems with my brake pump. While changing the brake fluid I did notice a fluid leak from the pressure swicht. I removed it and put a new seal. Apparently all went good, good pressure, no lights...I let the car sit overnight and found out that the leak still there. I removed again the switch and put another seal...but leaks again.

I noticed a **** by the end of the threads. Maybe the fluid is leak through this hole? Maybe the switch is faulty and leak internally?

Thanks in advance.
Augusto

ralt

Unfortunately its time for a new switch. Do not recommend trying to rebuild. If it fails at any speed other than zero, you will have a serious problem trying to stop car. Generally speaking you simply wont stop the car until it hits something else.

Augusto

For sure...I do not drive the car until I fix it.

The problem is I don´t know if it´s a seal issue (not the correct one) or an internal leak.

The switch is not cheap...I don´t want to buy one only for a bad seal.

Do thet leak internaly when they go bad?

fritz k.

i have had a faulty switch recently, the warning light turned on after a few miles, no leaking issues. can't believe that internal leak assumption 'cause the system pressure goes up to 180 bar. if there where an internal leak you should have a blast of brake fluid in the trunk.

on the other hand it not easy to fit that o-ring correctly, i remember that i had a few tries. i suggest to renew the O-ring (oem part) and give it another try.

dantm

How do you change this switch, do you need to relieve the pressure in the system such that liquid does not get out through the switch connection?

fritz k.

you have to pump the brake pedal while the switch is disconnected, this decreases pressure in the system. got myself a pressure gauge that fits the measure connection at the accumulator, helps checking function of the switch and remaining pressure in the system.

dantm

So when the switch is removed there's no internal pressure that is built in the system which makes brake fluid spill out everywhere (and/or at high pressure)?

Would the steps be:

(1) disconnect battery;

(2) connect pressure gauge at the accumulator;

(3) disconnect switch;

(4) press brake pedal repeatedly - not sure how this does not 'increase' rather than decrease the pressure in the system?

(5) connect new switch.

Optional - bleed system? Or not needed?

Thank you.

fritz k.

there is a proper description of the high pressure brake system of the turbos and C4´s in the workshop manual including the steps to check and replace the pressure switch. if you dont have access to the manual give me your mail address via PM.

dantm

PM sent...thank you.