Jeep Wrangler JK Radiator Replacement: How to Bleed the Cooling System!, by The Jeep Barn on YouTube. 28 min 37 s.
- Video length
- 28 min 37 s
- Time to do it
- 3 hours
- Difficulty
- Medium
- Steps
- 10
What you need
Steps
Park on level ground and let the engine cool completely. Never open the radiator cap or hoses while the system is hot, since pressurized coolant can scald you.
Lift the front of the Jeep on jack stands or ramps so the radiator sits higher than the engine. This helps air rise to the cap during bleeding.
Put the drain pan under the radiator petcock and open it to drain the coolant. Loosen the cap first to speed the flow, then close the petcock.
Disconnect the upper and lower radiator hoses and the overflow bottle line. Unplug the fan connector and remove the fan shroud bolts.
Unbolt the radiator mounts and lift the old radiator out. Compare it with the new one to confirm the hose necks and mounting points match.
Lower the new radiator into place and bolt the mounts back down. Reconnect the hoses, overflow line and fan connector, and tighten the clamps.
Fill the radiator through the cap with coolant until it reaches the neck, then fill the overflow bottle to the cold line. Leave the cap off for now.
Start the engine and let it idle with the heater set to full hot. Watch the coolant level and top it up as the level drops while air escapes.
Squeeze the upper radiator hose a few times to push out trapped air. Keep adding coolant until the level stays steady and no more bubbles rise.
Fit the cap, let the engine reach normal temperature and check the gauge. Shut it off, let it cool, then recheck the level and look for leaks.
Tips and common mistakes
Use only the coolant type Jeep specifies for your JK to avoid sludge and corrosion.
Run the heater on full hot during bleeding so coolant fills the heater core too.
Check the level again after the first few drives, since small air pockets can settle out.
Do not overtighten plastic radiator necks or hose clamps, as they crack easily.
Questions
How do I know all the air is out of the cooling system?
The coolant level stops dropping, the upper hose feels firm and hot, and the temperature gauge stays steady. Bubbles should no longer rise at the open cap.
Can I drive with air in the cooling system?
No. Trapped air causes hot spots and overheating, which can warp the head. Bleed the system fully before normal driving.
How much coolant does a JK radiator hold?
It varies by engine, so check your owner's manual. Buy more coolant than you think you need and keep the rest for top-ups.
This guide was drafted from the video's details and general task knowledge. It has not been checked against the full video. Check the video and relevant product instructions before following a procedure. Report a correction.
