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Unread 11-27-2011, 08:01 AM   #1
grey
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how to properly get air out of your cooling system

I need to flush my heater core but while I am doing that I wanted to replace all of my coolant. I am sorry if this has been disscused before but I am new to jeeps and I came from a BMW that had its own process on how to bleed the cooling system. Can anyone point me to a write up or explain to me how to properly refill and bleed all the air out of the system? I have a 1997 Sahara 4.0l I6. Any help is always appreciated.

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Unread 11-27-2011, 08:12 AM   #2
freeskier93
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I fill the rad up about 3/4 of the way, then start the engine and wait for it to heat up and the thermostat to open. Then I finish filling it up. Its a bit messy if your not careful because the escaping air can burp coolant out, but it is foolproof for getting all the air out.
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Unread 11-27-2011, 08:18 AM   #3
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buy this kit:
http://www.oreillyauto.com/site/c/de...0185&ppt=C0075

Step 1: drain the radiator into a 5-gallon bucket, cap it, and install the flush kit as directed by the instructions, then fill the system up with the garden hose. flush the system by leaving the radiator cap off as directed by the instructions.

Step 2: after flush is complete, turn the hose off and remove it. drain the system again and cap the flush T. refill the whole system (radiator & bottle) with distilled water and go for a drive to pump the distilled water around & get the system hot. or you can leave the radiator cap off till the engine gets hot enough to push water out.

Step 3: drain the distilled water out from the radiator. mix up a 50/50 mix of one gallon of Zerex GO5 (or your choice HOAT antifreeze) with one gallon of distilled water in a clean 5 gallon bucket. Use an anti-freeze tester to verify concentration. Dump that into the radiator. Remember, there will be roughly half a gallon of distilled water remaining in the engine block, so factor that into your mixture by testing the anti-freeze concentration repeatedly as you fill it. You can dump straight anti-freeze into the radiator at the end to cut the mixture to the proper concentration.

Step 4: as you fill, keep squeezing the top radiator hose. it will burp air out as you do so. once you can't burn any more air out with the hose, dump the remaining 50/50 mix into the overflow bottle till it reaches the "hot" mark. Now, start the jeep up and let it heat up enough to open the thermostat...going for a drive will make this happen quicker.

Step 5: top off the overflow bottle as necessary. remember, the thermostat should have a small hole in it to bleed air off, and heating the engine up pushes all the air to the thermostat and allows it to be pushed into the radiator, where it sits at the top of the radiator and is pushed into the overflow bottle, where its vented off.

Thats my modified version of how the FSM directs you to do it, and I've flushed three times like this and it works great for me.
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Unread 11-27-2011, 08:20 AM   #4
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^Similar, but on any vehicle I flush I'll jack up the front so the radiator cap is higher; I find this accelerates the air bleed. I also turn on the heater to prevent any heater valve or bypass from trapping air in there. Mostly an import issue, but I keep it a general practice.
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Unread 11-27-2011, 08:21 AM   #5
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An easy way to do it is to simply install a thermostat with an air bleed hole in it that is positioned at the top to let any trapped air escape through it through the top radiator hose and into the top of the radiator.

Like the one in the first photo. If you can't find one that has the bleed hole, you can drill your own like shown in the second photo.
thermostat-slot.jpg   thermostat-hole.jpg  
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Unread 11-27-2011, 11:20 AM   #6
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what if you are using a crossflow style of radiator? i wonder how well the air would get back to the cap.
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Unread 11-27-2011, 11:24 AM   #7
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How many TJ owners have a crossflow radiator? Who even makes a crossflow radiator for a TJ? Why would you even need a crossflow radiator for a TJ?
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Unread 11-27-2011, 01:20 PM   #8
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crossflows tend to be shorter and wider and i needed to clear some changes to steering and suspension. takes a bit of massaging but one will fit. nothing new. has been done before. seems like there are a couple responders who know their cooling.
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Unread 11-27-2011, 01:30 PM   #9
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Quote:
Originally Posted by fratis View Post
what if you are using a crossflow style of radiator? i wonder how well the air would get back to the cap.
I see no reason why a crossflow would change anything. Air bubbles still float because they're less dense than coolant. The inlet to the radiator is still at the top, the cap and overflow bottle are still opposite side of the inlet. Air will still rise to the cap side, and never make it deeper than the first stage of cross flow.

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Originally Posted by freeskier93 View Post
How many TJ owners have a crossflow radiator? Who even makes a crossflow radiator for a TJ? Why would you even need a crossflow radiator for a TJ?
Novak makes a crossflow for V8 conversions.
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Unread 11-27-2011, 02:28 PM   #10
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thats what i was hoping, thanks for the reassurance.
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Unread 11-27-2011, 05:17 PM   #11
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This is what I use @ the shop works great!http://www.amazon.com/Lisle-24610-Spill-Free-Funnel/dp/B001A4EAV0
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