I recently bought my truck and it has 160k+ miles on it and I have no idea when the coolant was replaced, so it’s on my list of things to do. Please throw in any advice/comments you can to what I have below - thanks.

The heater is hot and the engine seems to run at a normal temperature, so I’m thinking I just want to drain out the old stuff and replace it with new stuff. I’ve owned older cars in the past and if/when I tried to do a flush I seemed sometimes to create problems or make things worse, so since there doesn’t seem to be any problems right now I’m thinking a drain and re-fill will be good.

I noticed in the Owners Manual that they used the HOAT antifreeze (I’m going to use the Zerex-G05) and distilled water (to prevent rust/corrosion).

I want to drain and clear the overflow bottle. It looks like there are just two screws that hold on the upper fan shroud and then it (and the overflow) bottle should just come off (my shop manual isn’t clear on this).

If I can drain from the draincock it appears that the lower radiator hose is higher than the bottom of the radiator, so I’m not sure how much of the fluid will drain without maybe removing the lower radiator hose from the engine too.

To get to the lower radiator hose and draincock, it appears that the bottom plastic air dam has to be removed. It’s held in place by those plastic plug things. Should I plan on getting new plugs (because I’ll destroy the old ones getting them out)?

Once I drain things I want to re-fill with distilled water and run the engine with the heater on till hot then cool down and drain again. I probably do this a few times (depending on how much fluid I can drain) until things look clear. Once clear I’ll fill with the appropriate amount of Zerex and top off with distilled water.

To get the air out of the system my shop manual has the procedure for the 4.7 engine, but not for the 3.7. It recommends taking off the bleed screw, filling till it comes out the hole, put the screw back in, fill the radiator to the top, put the cap on, fill the overflow bottle, and start the engine and run it with the heater on until the engine gets hot. Stop and let it cool down. Re-fill the overflow bottle and repeat 3 times. Sound good?

 

Unless you are using harsh chemicals you shouldnt have any problem flushing the system. My buddy has 160k on his truck and he flushed his system using prestone radiator cleaner. It cleaned out the system way better than just straight flushing it(few of the cummins guys I know swear by it)
http://www.outdoorpros.com/Prod/Pres...FQ-e4Aodbj8AwQ

Im not sure on the 3.7's but I use a universal method that works on everything. Remove the cap and pull the lower rad hose. Drain and flush the system put it all back together and refill. Get it as full as possible(till its coming out the cap) then put it on and go for a little drive around the block and come back and top it off. I've never had a problem with air in the system.

 

Before he did the flush was he having any cooling problems or was his heater not very hot?

Yeah, I'm hoping the getting the air out of the system won't be bad. For the 4.7 the FSM says:

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

To purge the cooling system of all air, this heat up/cool down cycle (adding coolant to cold engine) must be performed three times.

 

After you refill the radiator get a couple bottles of Bars Leaks corrosion inhibitor from the parts store. And don't use distilled water.

 

You know, with all of my older vehicles I didn't use distilled water either (it wasn't good for the system). With this truck and my Jeep (2008) they now tell you to use distilled water.

From the Owners Manual:
Use only high purity water such as distilled or deionized water when mixing the water/antifreeze solution. The use of lower quality water will reduce the amount of corrosion protection in the engine cooling system.

From the FSM:
The use of aluminum cylinder blocks, cylinder heads and water pumps requires special corrosion protection. Only Mopar Antifreeze/Coolant, 5 Year/100,000 Mile Formula (glycol base coolant with corrosion inhibitors called HOAT, for Hybrid Organic Additive Technology) is recommended. This coolant offers the best engine cooling without corrosion when mixed with 50% distilled water to obtain to obtain a freeze point of -37°C (-35°F). If it loses color or becomes contaminated, drain, flush, and replace with fresh properly mixed coolant solution.

 

No he wasn't having problems with his heat. His anti freeze was just crappy looking so he figured he would get it good and cleaned before he refilled it.

 

OK - thanks for the info. Sounds like the flush worked out well for him.

 

Never used anything but tap water to mix the stuff I never had any problems

Im still not convinced on the premixed 50/50 stuff but its good as a top off.

 

Until I got these newer vehicles I've only used tap water myself.

I've never purchased the pre mixed stuff, I mix my own.

 

I just saw your Dakota Pic looks good nice clean