Porsche 996 TT, Repair Manual

Page: 727 / 2099

Checking the valve in the clutch save cylinder (2.1) is a direct measurement, while the valve in the
upper part of expansion tank cannot be directly tested (2.2)! •
If there is no hydraulic clutch boost after a hold time of 24 hours, at least one of the two valves is
definately damaged! •
Prior to the following check, ensure that the system is visually leak tight (externally)! •
2.1 Checking the valve (pressure−regulating valve) in the clutch save cylinder
1. Warm engine up to operating temperature (approx. 80°C).
Note
Take care when handling Pentosin! Wear protective glasses, gloves and protective clothing! •
If coolant hoses come into contact with Pentosin, thoroughly clean them with water
IMMEDIATELY! •
2. With the engine switched off and the accumulator filled (before switching off the engine, the engine must
have been run for approx. 20 seconds without depressing the clutch pedal), remove the plastic return line
−arrow−
from the expansion tank. To this purpose, push the red thrust ring in an axial direction, without
tilting, towards the tank and remove the line.
3. Collect the fluid which runs out in suitable measuring equipment (suitable container) and determine
the volume of fluid collected!
4. If more than 4 cm
3
is collected after a measurement period of one hour, the valve in the clutch save
cylinder is faulty and and the save cylinder must be replaced. Removing and installing clutch slave
cylinder => Removing and installing clutch slave cylinder.
2.2 Checking the valve (pressure−regulating valve) in the upper part of the
expansion tank
This valve can only be checked indirectly.
A fault exists if the hydraulic clutch boost function does not last for an entire 24 hours, but where the valve in
the clutch save cylinder is functioning correctly (Test 2.1).
einordnung
2. Checking valve (pressure−regulating valve) 664