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Old 09-07-2017, 12:07 AM
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JK 3.8 correct coolant flush procedure?

I'm looking to do the coolant flush on my 2011 JKU with about 80k miles. I can't seem to find a trustworthy writeup of the correct procedure. I have found a lot of guys sort of winging it, draining this or that, maybe filling it with a hose, maybe draining it again, then pouring in HOAT concentrate and hoping to get about 50/50. I'm fairly competent under the hood, so I could wing it, but I don't want FCA to try and blame me down the road if I have to call on my maxcare for something in the coolant system. To be honest, I'm not sure I'd trust "take it to the dealer" as the right answer either. I've known enough dealerships that don't do what they told you or cut corners otherwise.

Is there a certain procedure FCA intended? Can someone point me to it?

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Old 09-07-2017, 08:29 AM   #2
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Old 09-07-2017, 08:38 AM
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I saw that, but it only changes a small portion of the fluid. Drain and fill radiator is not the same as a coolant flush. Is that the procedure FCA expects at 60 mos. / 104k?


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Old 09-07-2017, 08:54 AM   #4
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This is from my shop manual for the 09, same setup as your 11.

CLEANING/REVERSE FLUSHING
CAUTION: The cooling system normally operates at 97 - 110 kPa (14 -16 psi) pressure. Exceeding this pressure may damage the radiator or hoses. Reverse flushing of the cooling system is the forcing of water through the cooling system. This is done using air pressure in the opposite direction of normal coolant flow. It is usually only necessary with very dirty systems with evidence of partial plugging.

CHEMICAL CLEANING
If visual inspection indicates the formation of sludge or scaly deposits, use a radiator cleaner, Mopar® Radiator Kleen or equivalent, before flushing. This will soften scale and other deposits and aid the flushing operation. CAUTION: Be sure instructions on the container are followed.

REVERSE FLUSHING RADIATOR
Disconnect the radiator hoses from the radiator fittings. Attach a section of radiator hose to the radiator bottom outlet fitting and insert the flushing gun. Connect a water supply hose and air supply hose to the flushing gun. CAUTION: The cooling system normally operates at 97 - 110 kPa (14 - 16 psi) pressure. Exceeding this pressure may damage the radiator or hoses. Allow the radiator to fill with water. When radiator is filled, apply air in short blasts allowing radiator to refill between blasts. Continue this reverse flushing until clean water flows out through rear of radiator cooling tube passages. For more information, refer to operating instructions supplied with flushing equipment. Have radiator cleaned more extensively by a radiator repair shop.

REVERSE FLUSHING ENGINE
Drain the cooling system (Refer to 7 - COOLING - STANDARD PROCEDURE). Remove the thermostat housing and thermostat. Install the thermostat housing. Disconnect the radiator upper hose from the radiator and attach the flushing gun to the hose. Disconnect the radiator lower hose from the water pump. Attach a lead away hose to the water pump inlet fitting. CAUTION: Be sure that the heater control valve is closed (heat off). This is done to prevent coolant flow with scale and other deposits from entering the heater core. Connect the water supply hose and air supply hose to the flushing gun. Allow the engine to fill with water. When the engine is filled, apply air in short blasts, allowing the system to fill between air blasts. Continue until clean water flows through the lead away hose. For more information, refer to operating instructions supplied

7 - COOLING
794
with flushing equipment. Remove the lead away hose, flushing gun, water supply hose and air supply hose. Remove the thermostat housing (Refer to 7 - COOLING/ENGINE/ENGINE COOLANT THERMOSTAT - REMOVAL). Install the thermostat and housing with a replacement gasket (Refer to 7 - COOLING/ENGINE/ENGINE COOLANT THERMOSTAT - INSTALLATION). Connect the radiator hoses. Refill the cooling system with the correct antifreeze/water mixture (Refer to 7 - COOLING - STANDARD PROCEDURE).
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Old 09-07-2017, 03:05 PM   #5
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I've never had any problems using a store bought flush kit. Just follow the directions. The only thing I change is adding a length of hose to the short discharge tube they supply.
if you see scale, or the color of the coolant looks strange, like kinda muddy, rusty color, then get a quality flushing chemical solution. There are several available. Again, follow the directions.
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