I made a copy of this a while back, hope it helps!
Viper GENII Coolant Change Procedure:
Viper coolant changes should be scheduled according to the Dodge recommended intervals, 36 months from date of manufacture and then every 24 months thereafter. Time is more on an issue here than mileage as vital anti-corrosion additives are being depleted constantly.
The process begins by safely raising the car about 17” or so. (Note: If you can, it’ll help to have the front on the car higher than the back during the “burping” session, so consider that as you plan your lift. You will need this clearance in order to open both the radiator petcock and the 2 block drain plugs, both of which are required to be removed for a complete draining.)
Make sure the heater temperature knob is in the “hot” position. This will allow coolant to drain from the heater core. Next, make sure the engine is cold and the system in unpressurized. If you can hold your hand on the block without discomfort and if you can squeeze the upper radiator hose completely, you should be OK. As an added precaution, prior to removing the coolant cap on the expansion tank, (passenger side of the engine compartment, See photo), place a rag over the cap, look away and twist the cap counterclockwise until you feel it click. This is the pressure release position. Push down, continue turning to remove.
Antifreeze is extremely poisonous! DO NOT siphon, let drain on the driveway or allow any animals to be exposed to it. Apparently it has a sweet taste that dogs love, but it will kill them if they drink it. Drain the radiator coolant into a bucket, pour into a closed container, and keep away from children. Plan to quickly and safely dispose at a local recycling center.
The service manual discusses a radiator petcock or valve, but in my case there was only an Allen keyed plug in the drivers side lower back of the radiator. The Allen key size is ¼ inch and note that caution must be taken as the surrounding metal is quite thin and will bend easily if you do not maintain straight even leverage on the plug. Allow the used coolant to drain completely into your bucket.
Once complete, you will need to drain each side of the block. There is one plug on each side, accessed underneath the engine, about the middle of the block, facing down. (See photo) They are female square sockets, perhaps 5/16” or 8mm, and are a plumbing style fitting. Unfortunately it’s difficult to find the correct size tool to remove, so I used a short 3/8 inch extension and ground down the four sides till it fit, approximately .320” square. You’ll find them tight and glued in, so it took a bit of snap to get them to loosen. If you are not changing the type of antifreeze, (say from green to extended life orange) and if you’re changing the coolant fairly consistent with factory recommendations, it probably isn’t ultra critical to drain the block, especially if you’re uncomfortable with the amount of torque that you’ll have to apply.
Once the block and radiator are completely drained, it’s time to drain and flush both the expansion tank and the coolant overflow bottle, which is located behind the passenger side front fascia (See photo). If you look in from your passenger side wheel well, you will see a 5 inch or so diameter rubber plug which is used to access the fog light. By removing that plug and inserting a bright light, you can see the level of the overflow through a slit in the wheel well. This is the tank that needs to be drained and flushed.
I used a $2.00 fish tank squeeze bulb siphon. The size of the tubing is a good fit and the correct hose is accessed at the neck of the expansion tank (See photo). Squeeze the bulb to create the vacuum / siphon, and let drain completely. Then, with a funnel, refill the overflow tank with clean water and repeat until drain water becomes clear. Leave empty at this time.
This procedure assumes that your system is relatively clean, but that you’d like to do a clean water flush to get out any minor impurities that remain, plus any trapped old coolant. If so, close up both the block and radiator plugs, remove the thermostat air bleed plug (see photo) with a 3/16” sized square plug wrench (purchased or made by grinding down a 1/4" extension) and slowly refill with distilled water. Again, you’ll find this plug very tight and glued. If you can find the right wrench and are comfortable with the amount of torque required to break it free, go for it. If on the other hand, you fear stripping the plug, (as some have) don’t open it. It’ll require removing the intake manifold and thermostat housing to repair it. Be cautious.
Slowly fill the expansion tank with distilled water which is available at any grocery store. Though you will drain it out again, it’s cheap and better for your engine than mineral laden tap water. Once you get water out of the opened thermostat bleeder, close it up and continue filling slowly until full. Avoid getting the serpentine belt wet, especially with antifreeze. If you do get antifreeze on it, flush with clean water.
Leave the expansion tank cap off at this point. Check and assure that the car is stable and safe with no one underneath (sorry for stating the obvious) firm parking brake and in neutral, then start the engine. Immediately add more water as the engine pulls in the fluid. Once filled, move over to the driver’s side and CAREFULLY squeeze the upper radiator hose to push the air in the hose into the radiator. No loose sleeves or clothing that could get caught in the belt. You should see the expansion tank gurgle as you do this, which give you the indication that you are burping correctly. After a while, you will notice the water naturally expanding out of the expansion tank, at that point, replace the cap in order to allow pressure to build. Once you feel the upper hose warming, you know the thermostat has opened and flow is occurring.
Note: If you did not open the thermostat bleeder to purge the air in the top of the block, you will notice a rapidly increasing engine temp as the water in the block heats beyond 195 degrees. This occurs because the thermostat is not submerged in the coolant and isn’t opening as quickly as it would if it was. Run the heater on full fan and max temp to give the engine a bit of cooling and soon the thermostat should open. If it doesn’t, shut the engine down before it gets too hot (watch the dash temp gauge) and let the heat soak open the thermostat. When it does, the temp will quickly diminish and the trapped air will purge into the expansion tank. Not a pleasant experience to witness, but unavoidable if you don’t open the bleeder plug as described above.
Again squeeze the hose to purge as much air out of the system as possible. At this stage, it is not critical to remove all of the air or shift the height of the car to maximize the purging. Our goal here is just to allow the water to flow and to flush any remaining old antifreeze from the system. After a few minutes of full coolant flow, (indicated by a warm upper radiator hose) you should shut down the engine and let it cool completely. This will take several hours so be prepared.
You could avoid the flushing step to save time and I feel it would be prudent to do so if you have not gone well beyond the recommended change intervals and if you’re replacing the coolant with the same type, i.e. the green stuff. If you are considerably beyond 36 months if it is the first change or well beyond 24 months otherwise, then the flush is a good idea. On the other hand you are changing to another type of coolant, such as Dexcool; (Orange) you should flush multiple times in order to maximize the benefit of the new coolant type. Being careful of course to allow a full cool down each time. This is not only for your safety, but also to prevent any massive temperature changes that could damage your engine. Lastly, if the coolant is so old that corrosion has occurred, I would strongly recommend a professional power flush rather than store bought caustic flushes.
Once the engine has cooled down you can drain everything again, same procedure as before. Once everything is drained, use a bit of Teflon tape or other anti-seize compound and tighten the plugs appropriately. Dodge does not publish (at least not that I can find) torque numbers for the drain plugs, so use common sense and don’t over tighten, just seal the system.
The capacity of the Viper cooling system (GEN II) is 12.8 quarts. (Check your manual to confirm your year). Given that and the recommended 50:50 mix ratio, I’d suggest (Method A) pouring in 6.4 quarts of your selected 100% antifreeze into the expansion tank first, and then continue filling with distilled water. This will result in the proper amount of antifreeze in your engine, but only if at least one flush was performed. Why, because any remaining pockets of liquid in the system are water, because of the flush. However, if you did not flush with water, then I would suggest (Method B) premixing one gallon of antifreeze with one gallon of distilled water at a time, then using that mix for your fill. Logic here is that somewhere within the system, pockets of old coolant lurk. If you use Method A, you could overcharge the mix. Again, you should have removed the thermostat bleed plug, filled until the coolant is at top of bleeder, replace bleeder carefully (with Teflon tape or antiseize) and continue filling.
Once you have the system filled, it’s time to burp again. This time, ONLY IF YOU CAN DO IT SAFELY, lower the rear of the car, so the radiator is as high as practical. You can also lower the driver’s side a bit as you want the air to move to the expansion tank and the higher the tank is relative to the cooling system, the easier it will be to purge. Again, firm parking brake, transmission in neutral, start the car and quickly add coolant as the engine pulls it in. Then carefully squeeze upper radiator hose to squeeze air towards radiator, replace expansion tank cap, continue squeezing and once upper hose is warm, shut down engine.
You can now lower the car. Next step is to refill the overflow bottle. Using the same hose you used to drain it, use a funnel and light in the fascia to verify level, refill the bottle using premixed antifreeze : distilled water at the 50:50 ratio until at proper level. Once filled, replace the fog light access plug and the hose onto the expansion tank.
The next few hours of driving will naturally purge any remain air in the system. I would occasionally turn on the heater to full to help purge that system and also keep my eye on the overfull bottle level as it will lower as the air is purged. After a few run cycles, the level should stabilize and mission considered complete.
*** THESE INSTRUCTIONS ASSUME THAT YOU ARE FAMILAR WITH WORKING ON CARS, ARE KNOWLEDGABLE ABOUT SAFE JACKING PROCEDURES, THE USE OF AUTOMOTIVE TOOLS AND PROCEDURES.
DO NOT PERFORM ANY PROCEDURE YOU ARE NOT COMFORTABLE WITH OR FEEL INSUFFCIENTLY INFORMED. YOUR LOCAL VIPER TECH IS A RESOURCE THAT YOU SHOULD UTILIZE IF YOU ARE UNSURE OF A PROCEDURE OR EXPERIENCE DIFFICULTY." ***
Thanks
