Dakota Quad Cab 2WD V8-5.9L VIN Z LDC (2002)
Radiator Cap: Component Tests and General Diagnostics
Cooling System Pressure Relief Testing
RADIATOR CAP-TO-FILLER NECK SEAL
The pressure cap upper gasket (seal) pressure relief can be tested by removing overflow hose from radiator filler neck nipple. Attach hose of pressure
tester tool 7700 (or equivalent) to nipple. It will be necessary to disconnect hose from its adapter for filler neck. Pump air into radiator. The pressure
cap upper gasket should relieve at 131 kPa (21 psi) and hold pressure at a minimum of 130 kPa (18.8 psi).
WARNING: THE WARNING WORDS -DO NOT OPEN HOT-ON RADIATOR PRESSURE CAP, ARE A SAFETY PRECAUTION.
WHEN HOT, PRESSURE BUILDS UP IN COOLING SYSTEM. TO PREVENT SCALDING OR INJURY, RADIATOR CAP SHOULD
NOT BE REMOVED WHILE SYSTEM IS HOT AND/OR UNDER PRESSURE.
Do not remove radiator cap at any time except for the following purposes:
1. Check and adjust antifreeze freeze point.
2. Refill system with new antifreeze.
3. Conducting service procedures.
4. Checking for vacuum leaks.
WARNING: IF VEHICLE HAS BEEN RUN RECENTLY, WAIT AT LEAST 15 MINUTES BEFORE REMOVING RADIATOR CAP.
WITH A RAG, SQUEEZE RADIATOR UPPER HOSE TO CHECK IF SYSTEM IS UNDER PRESSURE. PLACE A RAG OVER CAP
AND WITHOUT PUSHING CAP DOWN, ROTATE IT COUNTERCLOCKWISE TO FIRST STOP. ALLOW FLUID TO ESCAPE
THROUGH THE COOLANT RESERVE/ OVERFLOW HOSE INTO RESERVE/OVERFLOW TANK. SQUEEZE RADIATOR
UPPER HOSE TO DETERMINE WHEN PRESSURE HAS BEEN RELEASED. WHEN COOLANT AND STEAM STOP BEING
PUSHED INTO TANK AND SYSTEM PRESSURE DROPS, REMOVE RADIATOR CAP COMPLETELY.
Radiator Cap Testing
RADIATOR CAP
Remove cap from radiator. Be sure that sealing surfaces are clean. Moisten rubber gasket with water and install cap on pressure tester 7700 or an
equivalent.
Operate tester pump to bring pressure to 138 kPa (20 psi) on gauge. If pressure cap fails to hold pressure of at least 131 kPa (19 psi) replace cap.
The pressure cap may test properly while positioned on tool 7700 (or equivalent). It may not hold pressure or vacuum when installed on radiator. If so,
inspect radiator filler neck and cap's top gasket for damage. Also inspect for dirt or distortion that may prevent cap from sealing properly.
CAUTION: Radiator pressure testing tools are very sensitive to small air leaks, which will not cause cooling system problems. A pressure cap that
does not have a history of coolant loss should not be replaced just because it leaks slowly when tested with this tool. Add water to tool. Turn tool
upside down and recheck pressure cap to confirm that cap needs replacement.
