Cooling system flush procedure questions

Question

I am going to do a cooling system flush and after some reading and watching some YouTube videos I noticed that people take different approaches. So I have the following questions:

1. I understand that after you have drained the cooling system and filled it up with distilled water you are supposed to turn the car on letting the engine reach normal operation temperature to allow for the thermostat to open (in addition to turning the heat on so that the water also flows through the heater core). But I have also come across some people that suggest removing the thermostat. Is it necessary to remove the thermostat since it's going to open when engine reaches temperature?

2. The Haynes Repair Manual for my Nissan Maxima 2002 states to remove the two engine drain bolts on each side after draining the radiator. In case I am not able to locate these two bolts, Is that a strictly necessary step since hopefully as water runs through the system the engine block coolant should be pushed out by the water eventually correct?

3. In the videos I watched, the process of flushing is suggested to be repeated until clear distilled water comes out. I noticed that they put the radiator cap back on after each flush. I am going to use the yellow Spill Free Funnel from Lisle for this project. Can I just leave the funnel in the radiator at all times while doing this process and keep adding water until it comes out clean and this way I do not have to hustle with closing radiator cap, then waiting for it to cool down each time?

4. Finally, I have two gallons of 50/50 mix to perform the refill. Will these 2 gallons fill the overflow reservoir tank as well if I pour them through the radiator cap? Or do I have to fill the overflow tank separately?

Thanks in advance.

Answer 1

Is it necessary to remove the thermostat since it's going to open when engine reaches temperature?

No, it is not necessary to remove the thermostat. In fact, some cars you don't want to remove the thermostat while running the vehicle. The reason for this is that the thermostat can be used to direct coolant flow. If it is out, parts of the engine may not be getting coolant as designed. You do want to run it until the thermostat is open, though. This will ensure a proper flush.

In case I am not able to locate these two bolts, Is that a strictly necessary step since hopefully as water runs through the system the engine block coolant should be pushed out by the water eventually correct?

I wouldn't think it would be completely necessary, but it would make the process easier. It also helps to remove any sediment which may be trapped in the engine block. By removing any sediment, you'll allow the engine to cool at a better efficiency.

Can I just leave the funnel in the radiator at all times while doing this process and keep adding water until it comes out clean and this way I do not have to hustle with closing radiator cap, then waiting for it to cool down each time?

You should have the radiator cap on the radiator when running it up to temperature. This keeps the fluid inside the radiator. As the coolant in the system heats up, it will have a tendency to create steam. When this steam forms, it will want to push the coolant out of the system. With the radiator cap off of the system, it will overflow, causing an environmental mess, if you're not careful.

Will these 2 gallons fill the overflow reservoir tank as well if I pour them through the radiator cap? Or do I have to fill the overflow tank separately?

According to what I just read, the cooling system capacity, including the overflow tank, is 8 7/8 quarts. The "7/8ths" would seem to me to be the amount needed for the overflow, so, no, the two gallons you have would not be quite enough.