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Old 07-29-2013, 08:34 PM   #1
Join Date: Apr 2013
Location: Fauquier County, Virginia
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Cooling system issue

I have a 1991 YJ. I just replaced the radiator, both upper and lower hoses, thermostat (tested fine - it opens), radiator cap, and thermostat housing. Of course fresh coolant. Before changing all, flow through hoses and radiator was fine, heat was great. Now, heat is great, upper hose gets hot but lower hose is cool. When t-stat opens, back pressure forces antifreeze to spew from low hose. Can't figure out why this is happening. Any suggestions?

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Old 07-29-2013, 09:13 PM   #2
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Location: SoCal
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Air bubbles? Did you replace the water pump?

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Old 07-29-2013, 10:03 PM   #3

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Burp it, Let it cool a little and open cap. Run with cap open to see if you can pass the air bubble. YJs do this 4 or 6.
89 2.5 TBI, 4" RC lift, 1" Booms, SYE, Adams Driveshafts front and rear, Ford 8.8 with 4:88s, BFG 33X12.50X15, and a ton of other stuff.

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Old 07-30-2013, 10:25 AM   #4
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Originally Posted by jokerchief462 View Post
Burp it, Let it cool a little and open cap. Run with cap open to see if you can pass the air bubble. YJs do this 4 or 6.
This. Common issue.
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