HOW TO: Flush/Change Coolant

[BluPhant]

From the Service Manual, by request.

STANDARD PROCEDURE
STANDARD PROCEDURE - DRAINING COOLING SYSTEM 3.7L ENGINE
WARNING: DO NOT REMOVE THE CYLINDER BLOCK DRAIN PLUGS (Fig. 5) OR LOOSEN THE RADIATOR DRAINCOCK WITH SYSTEM HOT AND UNDER PRESSURE. SERIOUS BURNS FROM COOLANT CAN OCCUR.
(1) DO NOT remove radiator cap first. With engine cold, raise vehicle on a hoist and locate radiator draincock.
NOTE: Radiator draincock is located on the left/lower side of radiator facing to rear of vehicle.

(2) Attach one end of a hose to the draincock. Put the other end into a clean container. Open draincock and drain coolant from radiator. This will empty the coolant reserve/overflow tank. The coolant does not have to be removed from the tank unless the system is being refilled with a fresh mixture. When tank is empty, remove radiator cap and continue draining cooling system.

STANDARD PROCEDURE - REFILLING
COOLING SYSTEM 3.7L ENGINE

(1) Tighten the radiator draincock and the cylinder block drain plug(s) (if removed).
CAUTION: Failure to purge air from the cooling system can result in an overheating condition and severe engine damage.
(2) .Fill system using a 50/50 mixture of Mopar Hoat or Zerex G05 coolant and low mineral content water. Fill pressure bottle to service line.and install cap.
NOTE: The engine cooling system will push any remaining air into the coolant bottle within about an hour of normal driving. As a result, a drop in coolant level in the pressure bottle may occur. If the engine cooling system overheats and pushes coolant into the overflow side of the coolant bottle, this coolant will be sucked back into the cooling system ONLY IF THE PRESSURE CAP IS LEFT ON THE BOTTLE. Removing the pressure cap breaks the vacuum path between the two bottle sections and the coolant will not return to cooling system.
(3) With heater control unit in the HEAT position, operate engine with pressure bottle cap in place.
(4) Add coolant to pressure bottle as necessary. Only add coolant to the pressure bottle when the engine is cold. Coolant level in a warm engine will be higher due to thermal expansion. NOTE: The coolant bottle has two chambers. Coolant will normally only be in the outboard (larger) of the two. The inboard chamber is only to recover coolant in the event of an overheat or after a recent service fill. The inboard chamber should normally be empty. If there is coolant in the overflow side of the coolant bottle (after several warm/cold cycles of the engine) and coolant level is above cold full when cold, disconnect the end of the overflow hose at the fill neck and lower it into a clean container. Allow coolant to drain into the container until emptied. Reconnect overflow hose to fill neck.

STANDARD PROCEDURE - COOLING SYSTEM - REVERSE FLUSHING
CAUTION: The cooling system normally operates at 97-to-110 kPa (14-to -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-to-110 kPa (14- to-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 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).

 

[yoda13]

Great how-to Blu =D>

 

[Mangate]

How do you reach the cylinder drain plugs, from below or from above?

 

[jeepkj02]

How do you reach the cylinder drain plugs, from below or from above?

Step 1- remove engine
Step 2- drain cylinder block
Step 3- reinstall engine

....LOL!!

 

[thermos]

CAUTION: Failure to purge air from the cooling system can result in an overheating condition and severe engine damage.


How do you purge air from the cooling system? Has anyone had this problem when following the instructions above?

Thanks
Thermos

 

[jeepkj02]

After you finished draining out the old coolant (and replacing hoses/thermstat) refill the system. Leave the radiator cap off. Turn the heater on full and start the engine. Bubbles will start to come out of the coolant tank, top if off when needed, when bubbling stops cap off the tank turn heat back to normal/off and take for a spin. Next morning, before starting, check the tank and top off if needed.

 

[thermos]

After you finished draining out the old coolant (and replacing hoses/thermstat) refill the system. Leave the radiator cap off. Turn the heater on full and start the engine. Bubbles will start to come out of the coolant tank, top if off when needed, when bubbling stops cap off the tank turn heat back to normal/off and take for a spin. Next morning, before starting, check the tank and top off if needed.

Thanks for the reply.

Thermos

 

[Signcutter21]

I followed the instructions. but now when i'm filling up only got about 8 qts in before it's "full". The owners manuel and shop manual say 13 qt capacity. I pretty sure I got all the old stuff out and did a rinse too until it ran clear.

Should i let it run on high heat for a bit then refill as it's running or let it cool down?

Thanks,
Mike

 

[thermos]

I am about two weeks away from doing this

Two more questions I have are:-

1) It is essential that the engine block drain is removed (I would hate to strip the tread etc). The way I normally do it on other cars is cycle a few fills of water and then fill with coolant/distilled water. Is that ok?

2) I take it that the radiator cap is the yellow cap on the coolant bottle.

Thanks in advance
Thermos

 

[Mangate]

I am about two weeks away from doing this

Two more questions I have are:-

1) It is essential that the engine block drain is removed (I would hate to strip the tread etc). The way I normally do it on other cars is cycle a few fills of water and then fill with coolant/distilled water. Is that ok?

2) I take it that the radiator cap is the yellow cap on the coolant bottle.

Thanks in advance
Thermos

1) I wouldn't worry about striping the thread, you can't even see those screws let alone get them out. Unless you do as Jeepkj02 says and remove the engine first. Then you'll have easy access to repair the striped thread. Seriously, you would probably have to remove the exhaust where it joins the manifold on the drivers side, and the starter motor just to get to the screw. The passenger side you might just be able to do by feel. They need an allen key by the way, can't remember the size, maybe 1/4 or 3/16. I flushed the system with water then refilled with coolant till it ran out the same colour as going in, but I wasted probably half a gallon doing this.

2) Yes

 

[TheBlueKJ]

Fill system using a 50/50 mixture of ethyleneglycol antifreeze and low mineral content water.

Isn't this the wrong coolant?

 

[Leeann]

Isn't this the wrong coolant?

Yep. Need HOAT coolant and distilled water.

 

[TheBlueKJ]

Yep. Need HOAT coolant and distilled water.

I knew you needed the "hybrid organic acid technology" coolant for the 3.7 I just thought it funny that the manual tells you to put in the wrong coolant

 

[Leeann]

I knew you needed the "hybrid organic acid technology" coolant for the 3.7 I just thought it funny that the manual tells you to put in the wrong coolant

And they wonder why people put in the wrong stuff. Duh...

 

[FrankTimJr]

How do I remove the coolant reserve tank from a 2002 Liberty? Last week when my wife came home and shut the car off, all of a sudden all of the coolant started spewing out of the underside of the vehicle. I'm guessing it could be a cracked reserve tank, but I'm not sure how to remove it to check. I'm not a mechanic at all, so please dummy down the instructions. I'm hoping it's nothing more than just the tank.

 

[HoosierJeeper]

Where did it leak too? Closer to the front of the Jeep or towards the back of the engine compartment?

I had that once and it was right up front...turned out to be the water pump.

 

[FrankTimJr]

It was leaking towards the back of the engine compartment. It also started overheating a couple of weeks prior to this happening. Not overheating all the time, only when we're idling. When we're driving around the temp is normal. I seem to be having the same problem with my Grand Cherokee as well. It's fine when I drive, but when I sit at a traffic light or in a traffic jam, the temp goes up and up and up until it reaches the red zone.

 

[TwoBobsKJ]

It was leaking towards the back of the engine compartment. It also started overheating a couple of weeks prior to this happening. Not overheating all the time, only when we're idling. When we're driving around the temp is normal. I seem to be having the same problem with my Grand Cherokee as well. It's fine when I drive, but when I sit at a traffic light or in a traffic jam, the temp goes up and up and up until it reaches the red zone.

Sounds like your electric fan is on the fritz - when the Jeep is moving, sufficient air is moving through the radiator to keep things cool. When you stop moving the airflow stops and supposed to be bolstered by the electric fan. First step, take it to a shop and have them do diagnostics on the fan and associated electrical connections. If the fan is OK then the water pump (a la Hoosier Jeeper) could be the culprit.

A warning: These engines do NOT like to be overheated! Since it's already happened a couple of times with your Liberty you're playing with fire (ha, that's a pun!) and should get the cooling system looked at right away on both vehicles. Flush both systems and have them filled with HOAT-spec coolant ONLY - "universal" coolants are NOT to be used. Take it to a dealer to ensure the flush & fill is done correctly.

The coolant reservoir is removed by taking off two, 10mm bolts that hold the tank to the firewall. The tank then slides off a bracket to be taken off. There is a hose on the bottom and the overflow hose on the top that have to be removed if you're taking the tank completely off.

Let us know what you find out.

Bob

 

[FrankTimJr]

Thanks for the advise and I will be taking them to a shop to have them looked at. I will let you know what happens. I have a feeling it may be the fan because when I start the vehicle and let it sit for a while, the fan doesn't kick in at all.

 

[FrankTimJr]

Well, our 02 Liberty doesn't have a cracked coolant reservoir. So I have no idea why the coolant would have started spewing out of it after it was shut off. I wonder if it was clogged or something and that caused the reservoir to over flow? I refilled it with coolant and it seems to be fine now. But I know I really need to flush the system out completely and I am willing to do it myself, I just need to know how. I know there's a kit I can buy and use my garden hose with it. What and where do I disconnect to drain it and where do I connect the hose to? Does the entire operation take place at the reservoir or do I need to disconnect something by the radiator at the front of the engine? There is only one cap, on the reservoir, nothing on the top of the radiator itself. I know I can just take it to a shop and have them do it, but I can't afford that and need to do this on my own.

Our 04 Grand Cherokee, it's the fan that is causing it to overheat and a mechanic in my neighborhood suggested to bypass the relay switch so the fan is on 100% of the time. They said it's manually intensive job and shops will charge you a lot of money to change it. There are a couple of other vehicles they own that they bypassed the relay because of the same issue. They said it's too much of a pain in the **** to properly fix it. They are good mechanics and usually willing to help me out, but getting them to actually do the work is another issue entirely.

Thanks for all the help so far. At least I know I can come here and get good, experienced people to walk me through some of the things I can do on my own.