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Jeep Wrangler JK
JK General Discussion
2008 JK coolant reservoir bubbling
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<blockquote data-quote="cpwolf" data-source="post: 429399" data-attributes="member: 19674"><p>No, absolutely no. I just went through this with our 2008 Jeep JK. Boiling, you name it. </p><p></p><p>1. Up to 2012, Chrysler had manufacturer recommended HOAT for the JK. 2013 and newer OAT. </p><p>2. If you mix at all, there can be a chemical reaction that causes a gel effect, no bueno.</p><p>3. OAT alone in the older JKs, have caused boiling issues, total PITA on this whole "which coolant" thing in my opinion, but it matters.</p><p>4. I would replace the cap no matter what, even if it doesn't look like an issue.</p><p></p><p></p><p>Here's what I walked through on my 2008:</p><p></p><p>I did a non take apart flush if you will. I emptied the radiator. I filled the open space in radiator with distilled water. </p><p></p><p>Ran for 5 minutes, shut off and drained radiator, and put in distilled water. I repeated that until it was as clear as my patience would let me get it. (By the way, if the coolant coming out isn't orange, then someone put OAT in, not good). You may need to do a more intense flush to get it all out. </p><p></p><p>I then emptied the radiator and put filled with (non 50/50) so full strength HOAT ( pain in the rear to find, actually did at Autozone, O'Reilly or Advanced had no HOAT at all). So distilled water is in the engine etc, radiator emptied, and filled it with 100% orange HOAT. I did this on a hill so that the back of the engine didn't have bubbles.</p><p></p><p>I also pulled out the overflow and emptied it, then put 1" marks with a sharpee from the low mark to full mark to see easily for my testing, then I put it back and filled it to full.</p><p></p><p>From cold, I started the Jeep and let it idle. I had an OBDII bluetooth like the ones Chris has recommended on this forum from Amazon, with JSCAN software on my iphone. That way I saw the EXACT temperature the sensor was sending to the engine. </p><p></p><p>I kept checking the top hose and at the correct temp, it got hot when the thermostat opened, so that was fine.</p><p>I then watched, and there is an exact sequence when that stupid fan will come on, turn off, etc. I'll need to look, someone did a great write up where I saw all this, and mine followed that. The overflow level will change as it heats etc. </p><p></p><p>Just eliminating issues, thermostat and fan, and the sensor, if there is a crack letting air in, then it's letting coolant out, you would see it.</p></blockquote><p></p>
[QUOTE="cpwolf, post: 429399, member: 19674"] No, absolutely no. I just went through this with our 2008 Jeep JK. Boiling, you name it. 1. Up to 2012, Chrysler had manufacturer recommended HOAT for the JK. 2013 and newer OAT. 2. If you mix at all, there can be a chemical reaction that causes a gel effect, no bueno. 3. OAT alone in the older JKs, have caused boiling issues, total PITA on this whole "which coolant" thing in my opinion, but it matters. 4. I would replace the cap no matter what, even if it doesn't look like an issue. Here's what I walked through on my 2008: I did a non take apart flush if you will. I emptied the radiator. I filled the open space in radiator with distilled water. Ran for 5 minutes, shut off and drained radiator, and put in distilled water. I repeated that until it was as clear as my patience would let me get it. (By the way, if the coolant coming out isn't orange, then someone put OAT in, not good). You may need to do a more intense flush to get it all out. I then emptied the radiator and put filled with (non 50/50) so full strength HOAT ( pain in the rear to find, actually did at Autozone, O'Reilly or Advanced had no HOAT at all). So distilled water is in the engine etc, radiator emptied, and filled it with 100% orange HOAT. I did this on a hill so that the back of the engine didn't have bubbles. I also pulled out the overflow and emptied it, then put 1" marks with a sharpee from the low mark to full mark to see easily for my testing, then I put it back and filled it to full. From cold, I started the Jeep and let it idle. I had an OBDII bluetooth like the ones Chris has recommended on this forum from Amazon, with JSCAN software on my iphone. That way I saw the EXACT temperature the sensor was sending to the engine. I kept checking the top hose and at the correct temp, it got hot when the thermostat opened, so that was fine. I then watched, and there is an exact sequence when that stupid fan will come on, turn off, etc. I'll need to look, someone did a great write up where I saw all this, and mine followed that. The overflow level will change as it heats etc. Just eliminating issues, thermostat and fan, and the sensor, if there is a crack letting air in, then it's letting coolant out, you would see it. [/QUOTE]
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Jeep Wrangler JK
JK General Discussion
2008 JK coolant reservoir bubbling
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