Volvo C30 2007 Service And Repair Manual page 504

Perform a performance test of the engine's preheater. See: FUEL-POWERED PREHEATER, CHECKING
COOLANT PIPE FUEL-POWERED PREHEATER (B5254T3, B5254T7)
NOTE: The illustrations in this service information are used for different model years
and/or models. Some variation may occur. However, the essential information in
the illustrations is always correct.
PREPARATORY WORK
REPLACING PIPE COUPLINGS
Remove:
the engine coolant heater. See: FUEL FIRED BOOSTER HEATER (B5254T3, B5254T7)

the engine coolant hose(s) from the pipe coupling(s) on the engine coolant heater.

HINT: Mark out the internal location of the engine coolant hoses and the angle of the pipe couplings in
relation to the cover.
REMOVAL
REMOVING THE COVER OVER THE HEAT EXCHANGER
2012 Volvo C30 T-5
HVAC Climate Units - Removal, Replacement And Installation