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  #1  
Old 07-07-2015, 09:58 AM
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Question Air in coolant...

Hi everybody. First time user here as i bought my first Jeep just a couple of month ago. A 2001Grand Cherokee Limited 4.7.
Everything is fine, exept one thing bothers me. I can hear air trapped inside the HVAC system (that is, in the coolant fluid). First i thought it was water trapped in the sills, checked it and all drains seemed to be open and no water to be found. Went to the Jeep garage, they say that it's probably a head gasket, causing air into the coolant. But, the truck is not loosing coolant, and there's no white smoke coming from the exhaust, and no white sludge in the engine oil. The engine heat stays right in the dead centre on the dash all the time.
This baffels me? I can hear the air in the HVAC right after startup if i rev the engine right away up to 2.000 - 2.500rpm, and occasionally when i drive around.
Done the "clearing air from coolant" routine, no air came out.

What the heck could this be? I also like to point out that the HVAC does not go to full furnace hot when temp is turned all the way up, neither does it go ice cold when turned to "Lo" on both sides. (Just had the AC filled up) It does go hotter and colder though.

Please advice me if you have any idea...

Kind regards.

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Old 07-07-2015, 01:20 PM
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Re: Air in coolant...

I assume you understand the problem as a "gurgling" sound when you first take off in the morning or on start up? My '95 dodge truck / 5.2L does the same thing. Does the sound continue throughout your drive, or just on the first start up? If the head gasket isn't causing any issues, it's got to be an issue of getting the air to a high point where it can be released (jacking the front end up, etc).
Mike Sal
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Old 07-07-2015, 01:28 PM
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Re: Air in coolant...

That's exacly the issue, a "gurgling" sound that i can always hear when i start the car, and sometimes while i'm driving it...
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Old 09-26-2015, 02:04 PM
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Re: Air in coolant...

Well, the mystery continues. I've tried to get the air out a few times now, always by lifting the front end up. Nothing. I even let the car sit with the front end up for a few hours before checking for air.....nothing. But still i have the "gurgling"sound in the HVAC system. I've also noticed that the air doesn't get wery hot if I turn the heat all the way up to "HI", neither does it get ice-cold if i turn the temp down to "LO". It does get a bit hotter or colder though. And regarding if it's a head gasket thing, since july when I posted my first message I have not needed to add a drop of liquid to the cooling system....
Please...any ideas?
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Old 09-27-2015, 05:58 AM
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Re: Air in coolant...

I would have a look at the thermostat if its mounted correctly. It has a small bleed valve, which should sit on top. If its not, it could trap air in the system.
That the air does not get hot, could come from an air pocket in the heater core.
Is the radiator allways full with coolant ?
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Old 09-27-2015, 07:12 AM
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Re: Air in coolant...

Ok..good idea. I'll check the thermostat if it's been installed incorrectly. The radiator is always full when i check it, and the overflow tank is in he middle....
Thank you Frank, I'll keep you posted...
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Old 09-28-2015, 10:56 PM
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Re: Air in coolant...

Are you sure the blend doors aren't causing the sound? It sounds like they aren't functioning with the lack of high heat and low A/C. Sometimes a door servo makes a sound when it turns without engaging the door.


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Old 10-11-2015, 08:44 AM
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Re: Air in coolant...

Well...latest news...
Yesterday I changed the thermostat. Looked carefully at how it was installed before removing it, it was in correctly (but it wasn't a genuine one). Also i noticet that the bleed valve on it was loose and fine. So the problem isn't there.
I did put in a new genuine though, so now the thermostat should be 100%.
While re-filling the coolant i began with lifting the front end by approx 1ft from the ground. Then slowly adding the coolant both through the air bleed valve and to the radiator, taking about 5-10min pauses between fills (adding about 1-2liters each time). After it filled up i had the car standing with the front end raised for about half an hour, with both air bleed valve and the radiator open. I then started the engine and let it run on idle for about 10-15 min before closing the coolant system (some air came out while doing that).
I then went for a test drive. The heat gauge is right in dead centre. But still a gurgling sound in the heater core. And after the temp of the engine was up, if i put the heat all the way up to "Hi" it would get somewhat hot while driving but cool right down if the car stopped and ran idle.
So I started thinking, could the heater core be blocked? Letting in just a little of hot coolant while driving/under load, but barely while the engine runs idle?
So I took a laser thermometer and checked the temp of the pipes in and out of the heater core in the engine bay. There is maybe 10-15c difference max between them (or maybe barely that). That makes me think that the hot coolant is just going straight back.
What do you all think? Has anybody here had a problem with a blocked heater core in the HVAC system
Pbruecken. I'm pretty sure it isn't the blend doors because i can make this gurgling sound by simply reving the engine. And also i do hear the blend doors operate occasionally, that sound comes from behind the HVAC control centre in the dash, the gurgling sound comes from approx underneath the transmission selector stick...but thank you for the suggestion..
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Old 10-11-2015, 05:25 PM
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Re: Air in coolant...

It is indeed possible that the heater core is (partly) blocked. You can remove the heater hoses which are going to the heater core and see if there is a free flow. There is maybe some cleaning stuff which you could let sit in the core for a while and then back flushing it, so that any foreign material can be washed out.
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Old 02-22-2016, 11:40 PM
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Re: Air in coolant...

have you figured out the issue yet? I have the same issue with my WJ and tried bleeding the system and got some air out but still get the gurgling sound at start up and i i hit the gas hard.
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Old 02-24-2016, 05:56 AM
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Re: Air in coolant...

Yep. Found out that the heater core was partly blocked. Flushing it out by using water pressure, first the right way and then in reverse direction a few times did cure the problem about 80-90%. There still is a bit of a gurgling sound but it heats very well now.
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Old 02-24-2016, 07:21 AM
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Thumbs up Re: Air in coolant...

That's great to hear from all of us WJ owners. This seems to be a somewhat common problem with a lot of jeeps.
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