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AH64ID

Coolant Flush on a 3rd Gen

4 posts in this topic

This is a pretty simple maintenance procedure, but I thought I would throw my .02 out here for everyone to read.

First off the service manual has the procedure, and it really is quite simple.

DRAINING COOLING SYSTEM - 5.9L DIESEL ENGINE

WARNING: DO NOT REMOVE THE CYLINDER BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR DRAIN

PLUG WITH SYSTEM HOT AND UNDER PRESSURE. SERIOUS BURNS FROM COOLANT CAN OCCUR.

DO NOT WASTE reusable coolant. If the solution is clean, drain the coolant into a clean container for reuse.

1. Start the engine and place the heater control temperature selector in the Full-On position.

2. Turn the ignition off.

3. Do not remove radiator cap when draining coolant from reserve/overflow tank. Open radiator drain plug and

when tank is empty, remove radiator cap. If the coolant reserve/overflow tank does not drain, (Refer to 7 -

COOLING - DIAGNOSIS AND TESTING). The coolant need not be removed from tank unless the system is

being refilled with fresh mixture.

4. Remove radiator pressure cap.

REFILLING COOLING SYSTEM - 5.9L DIESEL ENGINE

Clean cooling system prior to refilling (Refer to 7 - COOLING - STANDARD PROCEDURE).

1. Close radiator drain plug.

CAUTION: Due to the use of the one-way check valve, the engine must not be operating when refilling the

cooling system.

NOTE: The diesel engine is equipped with two one-way check valves (jiggle pins). The check valves are

used as a servicing feature and will vent air when the system is being filled. Water pressure (or flow) will

hold the valves closed.

2. Fill the cooling system with a 50/50 mixture of water and antifreeze.

3. Fill coolant reserve/overflow tank to the FULL mark.

4. Start and operate engine until thermostat opens. Upper radiator hose should be warm to touch.

5. If necessary, add 50/50 water and antifreeze mixture to the coolant reserve/overflow tank to maintain coolant

level. This level should be between the ADD and FULL marks. The level in the reserve/overflow tank may drop

below the ADD mark after three or four warm-up and cool-down cycles.

In addition to the coolant flush I changed the thermostat. That procedure can also be found in the service manual.

5.9L DIESEL ENGINE

WARNING: DO NOT LOOSEN THE RADIATOR

DRAINCOCK WITH THE SYSTEM HOT AND PRESSURIZED.

SERIOUS BURNS FROM THE COOLANT

CAN OCCUR.

Do not waste reusable coolant. If the solution is clean,

drain the coolant into a clean container for reuse.

1. Disconnect the battery negative cables.

2. Drain cooling system until coolant level is below

thermostat (Refer to 7 - COOLING - STANDARD

PROCEDURE).

DR/DH ENGINE 7 - 65

WARNING: CONSTANT TENSION HOSE CLAMPS

ARE USED ON MOST COOLING SYSTEM HOSES.

WHEN REMOVING OR INSTALLING, USE ONLY

TOOLS DESIGNED FOR SERVICING THIS TYPE OF

CLAMP, SUCH AS SPECIAL CLAMP TOOL (NUMBER

6094).

CAUTION: A number or letter is stamped into the

tongue of constant tension clamps. If replacement

is necessary, use only an original equipment

clamp with a matching number or letter.

3. Remove radiator hose clamp and hose from thermostat

housing (1).

4. Remove the three water outlet-to-cylinder head

bolts and remove the water outlet connector.

5. Clean the mating surfaces of the water outlet connector

and clean the thermostat seat groove at the

top of the thermostat housing.

5.9L DIESEL ENGINE

1. Inspect thermostat seal for cuts or nicks. Replace if

damaged.

2. Install the thermostat into the groove in the top of

the cylinder head (2).

3. Install the thermostat housing (1) and bolts. Tighten

the bolts to 10 N·m (89 in. lbs.) torque.

4. Install the radiator upper hose and clamp.

5. Fill the cooling system with coolant (Refer to 7 -

COOLING - STANDARD PROCEDURE).

6. Connect the battery negative cables.

7. Start the engine and check for coolant leaks. Run

engine to check for proper thermostat operation.

I started off by simply draining the OE fluid into a bucket. It was still very red, no oil, or any contaminates that I could see. There was a little bit of some contaminate the showed up on the 3rd flush in the radiator, but looked liked what I have seen in every cooling system. On my 2nd flush the coolant was much warmer and now had a small oil film on the top. But my buckets were new and I attribute that to the new plastic and warm water, something to consider if you find the same conditions when you flush your system.

Since it was in the 20's and snowing yesterday I knew I would have a hard time making the coolant warm enough to open the thermostat to get a good flush, and removing the thermostat would cause a leak so I modified my OE thermostat. A freind of mine calls this a "Hawaii T-Stat".

Posted Image

So I drained the block/radiator 5 times. This may seem excessive, but consider this. A drain only gets about 4-5 gallons out, and its a 7.4 gallon system. So I wanted to ensure that I had as much of the old coolant out as possible.

What I would do is drain it, very slow about 30 minutes to drain, then fill it with distilled water, and start it. I would then top it off with the engine idling, put the pressure cap back on and bump the idle to 1100 and turn the EB on to get some heat. With my Hawaii T-stat and a 30ish degree garage (cant fit the truck in with the door closed) and the hood open the coolant would only get to 114*. I would let it get to 114* then turn the EB off and bump the idle to 1500 for a few minutes. Then shut it down, drain, and repeat.

This photo shows 1 gallon from each flush, with the full strength OE fluid on the left and an unopened gallon of water on the right. Drains 4 and 5 were identical in color, so I assumed that was about my point of diminishing returns.

Posted Image

For coolant I chose Zerex G-05, its HOAT and the factory fill. HOAT coolant is very difficult to find, and HOAT is not compatible with non-HOAT. I think I paid about $11/gal for it at NAPA. (Even thou its the OEM fluid, its not pink it's a yellow, which is really hard to see in the overflow tank)

Since its a 7.4 gallon system and only 4-5 gallons drain you MUST, I repeat MUST, use concentrated coolant, not a 50:50 pre-mix (even thou the service manual states 50:50 you don't want to do this, it will yeild you a 25-40% mix at most). You need to add 3.7 gallons of coolant to the system to have a 50:50 mix. First thing to do is to make 1.5 gallons of pre-mix, this is for the overflow tank. Fill the overflow tank to the FULL line and pour the rest of the 50:50 in the radiator. Now add the remaining 3 gallons to the radiator. Now, and only now, will you and any straight distilled water to the radiator. I was only able to get about .5gallons of distilled water in after the coolant, so even adding a gallon of distilled first will mess up your 50:50 desierd mix. Now start the enigne with the heater still on full and let it idle for a minute. Then add more distilled water to top it off. Repeat this once. Now you should be full enough that you won't pull your overflow reservoir below ADD.

Take it for a test drive, try to drive it a few miles after you have reached operating temp to get the coolant and water to properly mix throughout the block, radiator, and heater core. This was the hardest part for me, it was 19* outside, and there was 1-3" of snow on the roads. Even with my winter front fully closed I had to get up to 65-70 to get the T-stat to open and mix, then slow and accelerate again... But I got the t-stat to open 6-8 times and am confident I got a good mix.

I used 3.7 gallons of G-05 and approx 23 gallons of distilled water.

A little trick for pouring the coolant into smaller containers from the bucket. If you have ever put a funnel in a gallon container you know it bubbles and spills since the air cant escape. Try putting a toothpick in the opening of the container with the funnel, works great.

Posted Image

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I've changed out the coolant on my 04.5 twice now. I've never "flushed" the system although I had the means and products to do so. Judging by the condition of the coolant that I drained both times now, there was no need to "flush" the system........but that's just me.:2cents: Take it for what it's worth. Great write up!!

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I've changed out the coolant on my 04.5 twice now. I've never "flushed" the system although I had the means and products to do so. Judging by the condition of the coolant that I drained both times now, there was no need to "flush" the system........but that's just me.:2cents: Take it for what it's worth. Great write up!!

Looking at the coolant I pulled out, there probaly was no "need" but whate the heck... cant hurt :-) The OEM coolant is pretty good stuff.

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