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Cooling system

How do i get the remaining air out of my 4.0 jeep. I tried heater on high and heat cool cycle. Still no heat

Get the engine up to operating temperature. With the engine idling, loosen the upper radiator hose clamp. Insert a small flat bladed screwdriver between the upper radiator hose and the radiator hose neck. Allow the engine to continue to idle until all the air is purged from the cooling system and there’s nothing but coolant coming out of the radiator hose. Remove the screwdriver and retighten the hose clamp. Let the engine cool down and check the coolant level in the coolant reservior.


Thank You!

I drive up on to a set of ramps to get the radiator cap opening as high as possible. I leave the radiator cap off, start the engine, and turn on the heater. Once the engine warms up I top off the coolant as the air bleeds out of the cooling system. I use this trick on my 2000 Blazer.

Ed B.

There is no cap on the radiator on this vehicle.


You can remove the RETURN hose from the heater and allow the air to escape there. This hose usually runs between the heater core and the water pump…Do NOT apply any force to the heater core hose fitting!! You can cut that hose and install a “T” (flush) fitting making the job simple…

Thanks Caddyman! Would that be the top hose on the heater core? Seems logical the the air should escape from the top hose…

Also. With the heater on heat? Does it matter if the fan is on? I would guess not

Thanks for the help guys but ive tried all the above n still very little heat. Im currently waiting to hear if i bleed from top hose at heater core. I would think this would have to work

Here’s just an off the wall question. Have you verified the heater control valve is working? And/or if water is actually circulating through the core?

Heater control is working and water seems to be flowing through. I put a T in the top core hose and fluid does flow out when it running

Well, if you have coolant flowing out of the heater core, then you are looking at a different source of your no heat issue.

I would suspect a stuck open thermostat, causing the engine to run way too cool, which then gives no heat.

Next up would be a stuck mixer flap in the hvac system, which isn’t allowing the hot air from the heater core to get into the vent system in your truck.


Wanna buy a jeep?

Ive come to the conclusion that the heater core is not plugged but restricted. This must have happened when i drained the fluid to up the antifreeze level. Any input on this? Can i flush the heater core from the firewall via inlet outlet ???/

yes you can flush the core. just do not use high pressure. try flushing it both ways a couple of times. remember no high pressure

On my Grand Am, Caravan, Sundance, Shadow, and Escorts I’ve never had a problem with air in the cooling system after any kind of maintence. It works its way out through the normal flow through the system and the filling and draining of the resevior. Not saying that’s not the case with the Jeep, just suggesting some other items to check.

Examples of the heat going out on a few of my cars included a break in the heater core (constant loss of coolant and wet carpeting in the passengers footwell - fixed by replacing heater core), clogged/restricted flow in the heater core (fixed by running the heavy duty Prestone flush and fill thorugh it during a 3 hour road trip running errands), and a stuck thermostat (heat took 1/2 hour to come out after the entire cooling system was up to temp - fixed by replacing the thermostat).

With any of the above work be sure to stay vigilant in checking the engine temperature guage. If you are running in the red you are too hot and going to wreck the engine. If the guage doesn’t move off zero it could mean you are low coolant and the temp. sensor isn’t touching coolant to know what temperature it is, another good way to wreck the engine (ask my ex).

Good Luck

After trying everything suggested i ended up taking the hoses off the heater core and blowing by mouth backwards through the heater core. It worked! Thanks for all the help!