Cant get air out of cooling system.....ug

[jeeptorino68]

I cant believe I am here writing this. I have never had this much trouble with it. I have read every forum post I can find on the subject. So I'm here looking for further advice.

2002 3.7 with 240k miles. Engine swap late 2020.

Swapped the engine and have since had issues with air in the system. I have used the bleeder screw several times. I dont see any leaks. I dont lose coolant. The coolant looks clean and clear in the overflow tank.

What happens is. It seems ok, but while sitting at idle (fully up to temp) it will begin to make a bubbling sound after a few minutes and then when you rev the engine or start moving again you hear a huge rush of air through the heater core. It is always very audible from inside the jeep.

Help! Where is the air trapped!?

Last night I even unbolted the expansion tank and held it up at the cowl to be sure it was the highest spot to try and get the air up to the tank. No change....

 

[LibertyTC]

The persistent gurgling sound is probably coming from trapped air in the heater core.
I assume that only HAOT coolant has ever been added ? & that you have a MOPAR thermostat installed, that already has the bleed air pin included ?

Here is what I would recommend. With engine cold, now remove the cap & run jeep @ idle for 5 minutes while monitoring level.
Then shut Jeep off, did level drop at all ? if level dropped, add Hoat back to middle of tank & & replace cap.

Now get the Jeep real Hot like after driving it, slightly open bleeder screw with engine rpm set at 1700 rpm.
Rags or paper towels to absorb coolant, till no air bubbles are seen. Close bleeder screw.

Let it cool overnight & check the cold level again to middle of tank & repeat this time with cap left on.
Hopefully that gets rid of the trapped air, without any more gurgling sounds.

 

[uss2defiant]

I want to take a wild guess that tommudd would suggest doing a bunch of pedal to the metal launches

 

[Big Al]

I remember seeing a video where a guy removed the coolent lines right at the heater core to burp the system. Never tried it myself, and it's only a suggestion.
Do it cold and while the engine is running
I know prestone antifreeze used to make a small plastic tee joint that you could put inline on the heater hose. Sounds like a safer way to go.
Not sure if they still make them tee joints.

 

[jeeptorino68]

The persistent gurgling sound is probably coming from trapped air in the heater core.
I assume that only HAOT coolant has ever been added ? & that you have a MOPAR thermostat installed, that already has the bleed air pin included ?

Here is what I would recommend. With engine cold, now remove the cap & run jeep @ idle for 5 minutes while monitoring level.
Then shut Jeep off, did level drop at all ? if level dropped, add Hoat back to middle of tank & & replace cap.

Now get the Jeep real Hot like after driving it, slightly open bleeder screw with engine rpm set at 1700 rpm.
Rags or paper towels to absorb coolant, till no air bubbles are seen. Close bleeder screw.

Let it cool overnight & check the cold level again to middle of tank & repeat this time with cap left on.
Hopefully that gets rid of the trapped air, without any more gurgling sounds.

Yes assuming heater core too
Yes to that coolant type (zerex)
Kinda in the thermostat, different brand but has bleeder pin and yes in the right way and up...

I'll try those methods. Tried part 1 yesterday and didnt see a drop in the tank level will try part 2 and 3 tomorrow

 

[LibertyTC]

Here in the forums we can only recommend the quality proper fitting Mopar Thermostat.
It simply not worth risking any after market ones.

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[jeeptorino68]

Understood. I selected and installed the motor rad ultrastat, as I have not experienced a problem previously with non mopar thermostat. Thats not to say maybe this situation isn't caused by the thermostat. I will consider it.

Ive never had this much trouble before. But I've also never had the almost entire cooling system empty due to engine change. But even when I replaced my leaky heatercore years ago. There wasnt an issue like this getting air out.

 

[HoosierJeeper]

Mopar Tstat is made my Motorrad, at least the Mopar one I bought in 2017 was. Not sure they have different specs or not for aftermarket/OE. I wonder if the jiggle valve could be stuck? I've always burped mine one of two ways, just filling up the rad tank, letting it idle with the heat on till it burps, or filling it through the bleed screw, then top the tank off and let it idle till it burps. Normally takes 5-10 mins.

 

[tommudd]

I want to take a wild guess that tommudd would suggest doing a bunch of pedal to the metal launches

Really , oh my LOL

 

[JeepJeepster]

I've been noticing a bit of gurgling from my heat-core also. The way the 3.7 in the KJ is setup, the bleed screw isn't that important. The rad hose is higher than the bleed screw and the hose going to the overflow tank will let any additional air out.

I've noticed this for over a year in my kj... Not going to worry about it.

 

[jeeptorino68]

Mopar Tstat is made my Motorrad, at least the Mopar one I bought in 2017 was. Not sure they have different specs or not for aftermarket/OE. I wonder if the jiggle valve could be stuck? I've always burped mine one of two ways, just filling up the rad tank, letting it idle with the heat on till it burps, or filling it through the bleed screw, then top the tank off and let it idle till it burps. Normally takes 5-10 mins.

I have always uaed you option 2 wothout issue

I have been thinking of maybe pulling the thermostat to check it

 

[Robochop]

Just my 2 cents, but make sure you put the thermostat in the correct way as shown above. Most people put it in the wrong way! Also, make sure you turn up the heater temp switch before starting up the car to purge.

 

[jeeptorino68]

Ended up going back to a more OE style thermostat. That had a captured check ball rather than the other style air bleed of the ultra stat had. The thermostat housing has a special indentation that locates the air bleed. And viola no more air in the system now.

 

[LibertyTC]

This sounds good. More OE style?
What brand of thermostat is now installed?

 

[sumosumo]

I cant believe I am here writing this. I have never had this much trouble with it. I have read every forum post I can find on the subject. So I'm here looking for further advice.

2002 3.7 with 240k miles. Engine swap late 2020.

Swapped the engine and have since had issues with air in the system. I have used the bleeder ***** several times. I dont see any leaks. I dont lose coolant. The coolant looks clean and clear in the overflow tank.

What happens is. It seems ok, but while sitting at idle (fully up to temp) it will begin to make a bubbling sound after a few minutes and then when you rev the engine or start moving again you hear a huge rush of air through the heater core. It is always very audible from inside the jeep.

Help! Where is the air trapped!?

Last night I even unbolted the expansion tank and held it up at the cowl to be sure it was the highest spot to try and get the air up to the tank. No change....

Hey just disconnect the heater hoses and rev flush the core with a garden hose.then put your car on some kind of incline and burp the system .you hav to get the air out

 

[tommudd]

Hey just disconnect the heater hoses and rev flush the core with a garden hose.then put your car on some kind of incline and burp the system .you hav to get the air out

Doesn't work always , not on these KJs

 

[jeeptorino68]

Ended up going back to a more OE style thermostat. That had a captured check ball rather than the other style air bleed of the ultra stat had. The thermostat housing has a special indentation that locates the air bleed. And viola no more air in the system now.

Well turns out that was a bit if a short term fix. Air came back a few weeks later...
I have been very busy so hadnt had time to post.
What gives!? How does air keep getting into the system. There is no external leak. I dont believe it is leaking into the exhaust. No white smoke.

 

[uss2defiant]

Have you tried pressurizing your system with a pressure tester overnight?

 

[Ksat]

It sounds like you could have a small leak in the head gasket which is allowing combustion gases to get into the coolant. My truck has this issue. I get the same gurgling sounds in the heater core along with an occasional higher than normal temp gauge reading. I have no white smoke in exhaust, no loss of coolant and no coolant in the oil (or oil in coolant). I pressurized all 6 cylinders with compressed air at TDC, removed the radiator cap and noticed the coolant rise up and out of the radiator on 2 of the cylinders which confirmed this problem. You might want to perform a similar test on your Jeep or do a simple block test, which would probably be easier. .

 

[jeeptorino68]

Have you tried pressurizing your system with a pressure tester overnight?

No, I'll see about doing that