cooling

Radiator Cap

for 1970 AMC Rebel Machine 390ci V8 · RWD

Editorial review:Chris Hackleman — Master Technician · 20+ years · Jeff Moore — Master Mechanic · 20+ years

Difficulty

Easy

Time

12 min

Tools

Steps

✓Expert-verified. Personally reviewed and approved by OLP's master technicians (Chris Hackleman & Jeff Moore — 20+ years each). Always follow the vehicle's factory service information and torque specs.

Replace the radiator cap on a 1970 AMC Rebel Machine to restore proper cooling system pressure and prevent coolant loss.

Warnings

⚠️Never remove radiator cap when engine is hot or running. Pressurized coolant can cause severe burns. Allow engine to cool completely before beginning this procedure.

⚠The 1970 Rebel Machine uses a pressurized cooling system. Always verify engine temperature is below 100°F before opening the cooling system.

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 cap × 1 — 16 PSI pressure rating recommended for 390ci V8

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 completely cool to the touch
Park vehicle on level surface and engage parking brake
Locate radiator cap at the top of the radiator in the engine compartment

Procedure

1
Verify Engine Temperature
Place your hand near (not on) the radiator cap and upper radiator hose to confirm the engine is completely cool. If any heat is detected, wait longer before proceeding.
2
Prepare Work Area
Place a shop rag or towel over the radiator cap to protect against any residual pressure or coolant spray.
3
Remove Old Radiator Cap
With the rag in place, press down firmly on the radiator cap and rotate counterclockwise to the first stop. Pause to allow any remaining pressure to release. Then press down again and continue rotating counterclockwise to fully remove the cap.
4
Inspect Radiator Filler Neck
Examine the radiator filler neck sealing surface for damage, corrosion, or debris. Clean any debris or corrosion with a clean rag. Check for cracks or deformation that could prevent proper seal.
5
Inspect Old Cap
Check the old radiator cap gasket and pressure seal for cracks, hardening, or deterioration. Verify the pressure rating stamped on the cap (should be 16 PSI for this application). This helps confirm the correct replacement part.
6
Install New Radiator Cap
Place the new radiator cap onto the filler neck, ensuring it is seated properly. Press down firmly and rotate clockwise until it stops at the fully locked position. You should feel a positive engagement.
7
Verify Installation
Confirm the cap is fully seated and locked by attempting to lift it gently without pressing down. It should not come off. Check that the cap sits flush and even on the filler neck.

Reassembly

No additional reassembly required for this procedure

Verification

Start the engine and allow it to reach normal operating temperature while monitoring for coolant leaks around the radiator cap
Check coolant level after engine reaches operating temperature and top off if necessary through the radiator cap opening
Verify no coolant spray or leakage occurs from the cap area during warm-up and after reaching operating temperature
Confirm temperature gauge reads in normal range and no overheating occurs during a short test drive

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