Cooling System Pressure Test

This procedure tests the cooling system for leaks using a pressure tester to identify external leaks, internal leaks, or compromised system components before they cause engine damage.

Warnings

Tools required

Parts

• ACDelco DEX-COOL coolant (if system requires topping off) × 1 — Use OEM specification

Preparation

1. Ensure engine is completely cold to the touch before beginning work
2. Park vehicle on level surface and engage parking brake
3. Allow at least 2 hours cooling time if vehicle was recently operated
4. Verify coolant level is visible in recovery tank - top off if low before testing
5. Have adequate lighting to inspect all cooling system components

Procedure

1. 1

   Remove radiator cap and inspect system
   Slowly turn the radiator cap counterclockwise to the first detent and allow any residual pressure to release. Once pressure is fully released, press down and continue turning to remove cap completely. Visually inspect coolant condition - it should be orange/red and free of contamination, oil, or excessive debris.
2. 2

   Check coolant level
   Look into radiator filler neck to verify coolant level is at the top of the radiator. If low, add ACDelco DEX-COOL coolant mixture (50/50 with distilled water) until full. The system must be completely full for accurate pressure testing. Check coolant recovery tank and ensure level is between MIN and MAX marks.
3. 3

   Install pressure tester adapter
   Select the correct adapter from your pressure tester kit that fits the 2014-2018 Silverado radiator neck (typically a GM-style adapter). Install the adapter onto the radiator filler neck, ensuring it seats properly and forms a complete seal. The adapter should thread on or lock securely depending on your kit design.
4. 4

   Attach pressure tester and pressurize system
   Connect the pressure tester to the installed adapter. Slowly pump the tester until pressure reaches 15 PSI (the typical operating pressure cap rating for this system). Do not exceed 18 PSI. Monitor the gauge - pressure should hold steady without dropping.
5. 5

   Observe pressure gauge for initial leak indication
   Watch the pressure gauge for 2-3 minutes without touching the vehicle. A properly sealed system should maintain pressure with minimal drop (less than 1 PSI in 2 minutes is acceptable). A rapid pressure drop indicates a significant leak. Note the initial pressure reading and time.
6. 6

   Inspect radiator and hose connections
   With system still pressurized, visually inspect the radiator for coolant seepage, paying close attention to the plastic end tanks, core seams, and petcock drain valve at bottom. Check both upper and lower radiator hoses at connection points to radiator and engine. Look for wet spots, drips, or swelling. Run your hand (with a shop towel) along hoses to feel for moisture.
7. 7

   Check water pump and thermostat housing
   Inspect the water pump area on the front of the engine for coolant weepage from the weep hole or gasket surface. Check the thermostat housing on the front of the engine for leaks at gasket surfaces. Look for coolant staining or fresh wetness indicating active leaks under pressure.
8. 8

   Inspect heater hoses and bypass connections
   Trace heater hoses from the firewall connections forward to the engine. Check all clamp areas and hose ends for leakage. Inspect any coolant bypass connections and steam vent hoses near the throttle body area. Use inspection mirror to view areas difficult to see directly.
9. 9

   Check overflow tank and hose
   Inspect the coolant recovery tank for cracks, especially at mounting points and connection nipple. Check the overflow hose from radiator to recovery tank for leaks or disconnection. Verify tank cap is sealing properly.
10. 10

    Inspect engine block and cylinder heads
    Look along both cylinder head gasket surfaces where heads meet the block for external coolant seepage. Check freeze plug locations on sides of engine block. If accessible, inspect rear of engine and transmission bellhousing area for coolant presence which could indicate internal leak into cylinders.
11. 11

    Monitor pressure and check for internal leaks
    After completing external inspection, check pressure gauge reading again. If pressure has dropped significantly but no external leaks are visible, remove oil filler cap and dipstick to check for milky oil (coolant contamination) or coolant smell in crankcase, indicating internal head gasket leak. With system still pressurized, remove one spark plug and check for coolant in cylinder if internal leak is suspected.
12. 12

    Release pressure and remove tester
    Once inspection is complete and all findings are documented, slowly release pressure using the tester's release valve. Wait until gauge reads zero PSI. Disconnect pressure tester and remove adapter from radiator neck. Wipe radiator filler neck area clean with shop towel.
13. 13

    Reinstall radiator cap and verify coolant level
    Check coolant level in radiator one final time and top off if needed. Install radiator cap by pressing down and turning clockwise until it locks into place at both detents. Verify coolant recovery tank level is correct between MIN and MAX marks.

Reassembly

1. No disassembly is required for this diagnostic procedure
2. Ensure radiator cap is properly installed and fully seated
3. Wipe any spilled coolant from engine bay surfaces to prevent future confusion during leak diagnosis

Verification

• If system held 15 PSI for at least 10 minutes with less than 2 PSI drop and no leaks were found, cooling system integrity is confirmed
• If leaks were identified, mark their locations and perform necessary repairs before returning vehicle to service
• Start engine and allow to reach operating temperature, then verify no leaks appear under normal operating conditions
• Re-check coolant level after test drive as air pockets may have been released during pressure testing

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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