Coolant Reservoir: Testing and Inspection

Checking Expansion Tank

NOTE: Cap has 3 important functions:

1. It opens at pressure of 0.9-1.15 bar (13-17 psi) allowing flow to expansion tank

2. It opens at a vacuum of 0.02-0.1 bar (0.3-1.45 psi) allowing flow from expansion tank

3. It seals radiator neck

Only item 1 can be checked with tester. If it is suspected that items 2 and 3 are not in order, replace cap.





- attach cap on tester
Stant tester ST-255 A, AC-PCT-3 or equivalent

- apply pressure of 0.9 to 1.15 bar (13-17 psi)
if pressure relief valve opens within this range, cap is OK