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Frango100 05-09-2012 02:43 PM

Air bubbles in cooling system
Changed the radiator 2 months ago, but now, when i start the jeep and accelerate a bit, i can hear the sound of air bubbles passing the heater core:confused:. After a minute or so all is normal again. The coolant level is normal and no bubbles in the expansion reservoir. Can this still be some trapped air and if so, how do i get rid of it? Removing the bleed plug on top doesn't help. I know that the thermostat has a small ball valve which should be at the top side, which will let any trapped air escape from there. The thermostat can't be installed wrongly infact, due to the recesses in the valve, the seal and the housing.
Any ideas?

amw5 05-09-2012 04:10 PM

Re: Air bubbles in cooling system
You could try running the heat on high for a while and see if that helps free up some air. Park the Jeep on an incline so that the radiator is higher than the heater core and pop the radiator cap off. You may get some careful, it's hot! Unscrew the bleed cap. Start your car's engine and let it idle until the engine warms up.

Once it gets to operating temperature, turn on your heater and fan to the max. Let the car idle for a few minutes and watch the level of coolant in the radiator. You'll see occasional bubbles...keep adding coolant slowly until you see a steady stream of coolant without bubbles and burps. Screw the bleeder cap back on and top off the radiator at this point, fill the reservoir to the proper level, and replace the radiator cap.

Hope that helps.

Frango100 05-09-2012 08:48 PM

Re: Air bubbles in cooling system
But it is so strange that this now only pops up 2 months after opening the system. I will give it a try to bleed it again on a slope, lets see.

01grand 05-10-2012 01:56 PM

Re: Air bubbles in cooling system
Mine did that too when I replaced the hose clamps that failed a few months ago. Except for me it was a week or 2 later that I noticed the air bubble noise. I checked the bleed plug and the coolant was full there and at the rad and in the reservoir, so I let it go a bit longer and it seems to have worked itself out.:confused:

bacernate 05-13-2012 05:28 PM

Re: Air bubbles in cooling system
I work on cars for a living, and in our area there are lots of jeeps and everyone i've seen has this noise in the core. Both of the v-8 wj's i own do this. Before and after heater core replacement. The only thing I can suggest if it really bothers you is to put a flow reducer on the inlet hose to the heater core.

2005JGC 05-14-2012 12:43 PM

Re: Air bubbles in cooling system
I just did a heater core in a 2002, When I do cooling system repairs I use a radiator funnel which ensures it is the highest point in the cooling system, I also like to rev it up 2000-3000rpms for a minute or two here and there to really get the coolant circulating. Obviously this is done after the initial bleed with the bleeder screw.

hoffmanestates 05-23-2012 08:48 PM

what also helps is a air powered coolant refiller. it puts a vacuum on the system. ya flip some knobs ands it sucks coolant from bucket filling void in system

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