Component Tests and General Diagnostics

17 00 009 Checking cooling system for water leaks (N74)

Special tools required:





Warning!
Danger of scalding!
Only perform this work after engine has cooled down.





Protective measures/rules of conduct:
^ Wear safety goggles
^ Wear protective gloves

^ Observe national/country-specific regulations





Important!
Risk of slipping due to coolant on the floor.
Risk of injury!

Catch and dispose of drained coolant in drip tray (1) and if necessary special tool 00 2 030 (universal hydraulic lifting equipment).

Recycling:
Observe country-specific waste-disposal regulations.





Checking pressure drop in cooling system:
Open cap on coolant expansion tank. Fit special tools (1) 17 0 101 and (2) 17 0 113.

Build up gauge pressure and wait approx. 2 minutes.

Cooling system is impervious to leaks if pressure drop is max. 0.1 bar.





Checking pressure relief valve in cap:

Note:
While driving the vehicle at high outside temperatures, depending on the design, the pressure relief valve in the sealing cap can open slightly and air, together with dissolved coolant, can escape. This coolant vapor condenses on the surface of the expansion tank and leaves traces of coolant after the vehicle cools. These traces of coolant do not indicate a defective cap. When the vehicle has been parked up for an extended period of time, the residual escaping coolant can cause the pressure relief valve in the cap to stick; therefore check the cap again 2 to 3 times.

Replace the cap only after you have checked three times and there is an incorrect opening pressure.





Checking pressure relief valve in cap:
Screw cap (1) onto special tool 17 0 114.

Build up pressure with special tool (hand pump) 17 0 101; observe pressure gauge to ascertain when opening pressure is achieved.

Compare opening pressure of pressure relief valve.