cooling

Radiator Cap

for 1994–2007 Dodge Ram 2500 5.9L I6 Cummins Diesel · 4WD

Difficulty

Easy

Time

12 min

Tools

Steps

✓Fact-checked. Built from OLP's spec database, then independently fact-checked line by line with every correction applied. Master-tech sign-off by Chris Hackleman is queued. Cross-check torque values against the factory manual, and stop if anything looks unsafe. How our data is made.

Replacement of the radiator pressure cap on a 1994-2007 Dodge Ram 2500 with 5.9L Cummins diesel engine.

Warnings

⚠️Never open the radiator cap on a hot engine. Pressurized coolant can cause severe burns. Wait until engine is completely cool to the touch.

⚠Ensure replacement cap meets the correct pressure rating (typically 16 PSI). Incorrect pressure rating can cause cooling system damage or overheating.

Tools required

Shop rag or towelEssential

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Parts

Radiator pressure cap × 1 — 16 PSI pressure rating, verify specification

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Preparation

Ensure engine has been off for at least 2 hours and is cool to the touch
Park vehicle on level ground and engage parking brake
Verify replacement cap matches pressure rating of original (stamped on top of cap)

Procedure

1
Verify Engine Temperature
Touch the radiator and upper radiator hose to confirm the engine is completely cool. The cooling system operates under pressure and hot coolant can cause severe injury. If any warmth is detected, wait longer before proceeding.
2
Relieve Cooling System Pressure
Place a shop rag or towel over the radiator cap. Slowly turn the cap counterclockwise to the first stop position and allow any residual pressure to escape. Listen for hissing sounds and wait until all pressure has been released before continuing.
3
Remove Old Radiator Cap
Once all pressure is released, press down on the cap while continuing to turn counterclockwise until it can be lifted free from the radiator neck. Inspect the radiator filler neck seal surface for corrosion, damage, or debris that could prevent proper sealing.
4
Inspect Coolant Level and Condition
With the cap removed, visually check the coolant level in the radiator. It should be visible near the top of the filler neck. Note the coolant color and check for contamination, oil, or debris. Pre-2002 models typically use conventional green ethylene glycol coolant, while 2002 and later models use HOAT (G-05) coolant. Top off if low using the coolant type appropriate for your vehicle and do not mix coolant types.
5
Clean Radiator Neck
Wipe the radiator filler neck sealing surface with a clean shop rag to remove any dirt, old coolant residue, or corrosion. Ensure the neck is clean and smooth for proper cap seal.
6
Install New Radiator Cap
Place the new radiator cap onto the radiator filler neck, aligning the cap tabs with the neck slots. Press down firmly and turn clockwise until the cap locks into position with a firm click. Verify the cap is fully seated and locked by attempting to turn it further.

Reassembly

No reassembly required for this procedure

Verification

Start engine and allow it to reach normal operating temperature while monitoring for leaks around the radiator cap
Check that coolant reservoir level remains stable and no coolant is being expelled from the overflow tube
After test drive, re-check radiator cap for proper seating when engine is cool
Verify no coolant smell or visible steam during operation, which would indicate improper sealing