My first post here although I have frequented this forum for the last 5 years ever since I bought the 2010 Pathfinder. I really appreciate collective wisdom of this board.

I am a DIY guy and change all the fluids myself. I also purchased service manual soon after purchasing vehicle to make sure I can fix/maintain anything I can. The closed cooling system on Pathfinder puzzles me, and so I have been postponing simple coolant drain and fill. I now hit 60K miles so it’s time to do it, yet after reading service manual and googling this and other Nissan forums, I cannot find good directions on how to properly refill the system. I was hoping someone can provide detail instructions and/or link describing such.

Service maual calls for the “Tool” which I don’t have and don’t intend to buy. I do have Lisle funnel that I use on other cars with traditional cooling systems, and it works great. Many members also report DIY coolant change without the tool, so I wonder how they do it.

Draining part seems easy following service manual:

1. Turn ignition switch ON and set temperature control lever all the way to HOT position or the highest temperature
position. Wait 10 seconds and turn ignition switch OFF.
2. Remove the engine front undercover using power tool.
3. Open the radiator drain plug at the bottom of the radiator, and
remove the reservoir cap.

Refilling the coolant:

Close the radiator drain plug.
Set the vehicle heater controls to the full HOT and heater ON position. Turn the vehicle ignition ON with
the engine OFF as necessary to activate the heater mode.
3. Remove the vented reservoir cap and replace it with a non-vented reservoir cap before filling the cooling
system.
4. Install the Tool...

OK, no tool. So how do you guys do it? It appears to me that after draining coolant from radiator, you close the plug on the bottom, remove the reservoir cap and replace it with the one from the radiator. Than you should be able to refill the radiator by using the Lisle funnel, but I am not really sure.

Questions:

1. Will the reservoir tank empty its fluid during draining, or will it remain there?
2. Can I just use Lisle funnel on the radiator to properly refill radiator and burp the system?
3. Will any extra coolant just flow into the reservoir during refilling?
4. Does the reservoir itself needs to be filled before or during this process?

Thanks so much for your help!

If you use the Lisle funnel on the radiator, fill the radiator and then start the engine, it will blow coolant out of the radiator and make a huge mess; trust me, I know from experience! This is the way I've always done it:

After you've drained the system and re-installed the drain plug and have both front and rear heaters set to maximum heat, fill the radiator with coolant and install the radiator cap. Fill the reservoir to or slightly above the "MAX" line on the tank. Jack up the front of the vehicle as much as you safely can; this helps air in the rear system work its way to the front. Start the engine and let it idle a minute or two, check the level in the reservoir and add if necessary, then install the reservoir cap. Run the engine at approximately 2500-3000 RPM for at least 20 minutes; if you don't have hot air coming out of the vents at this time, continue to run until you do. Shut the engine off and lower the vehicle. Re-check the reservoir level (remember the system is under pressure and the reservoir cap is the pressure vent cap in the system, so you may want to let it cool down a little if you can't see the level without removing the cap) and add if needed to return the level to the "MAX" line. Road test and make sure it doesn't run "hot" and also make sure you have heat coming from the vents in heater mode. If all is good, you're done. I would re-check the level the next day in the reservoir. If it does run hot or you have insufficient heat, repeat the process of raising the front end and running the engine at 2500-3500 RPM.

Thanks smj,

I really appreciate it! I have a few clarifying questions before I do this.

When you drain, do you follow service manual, meaning you unscrew the drain plug and remove the reservoir cap only, while leaving radiator cap on? Please let me know. Also, does the coolant from the reservoir drain as well, or does it remain there?

On a refill process - what I noticed just observing the system is that when you start the engine, it sucks the coolant in from the reservoir so it seems like it’s low, but when the engine cools off, it expands back to the MAX line. I assume that’s why you recommend to add if necessary when you start the engine. So my question is to what line do you add coolant in that first minute after you turn the engine on? I would be afraid to add to the MAX line as that may be too much coolant in the system – once the engine cools off the reservoir may very well be over the MAX line. Do you just keep it at MIN line before you put the vented cap on?

Finally, it appears to me that the coolant level in the reservoir should not be checked when the engine is hot (like the MAX line would indicate in a traditional system). It should only be checked when the engine is cold, and the level should be at MAX when cold. So there should be no need to check the coolant level while the engine is still hot because it may not be accurate. Am I wrong on this? Otherwise, the way you do it makes perfect sense, and I am glad I did not try using the funnel.

I don’t want to overthink this, but I also don’t want to ruin anything. Thanks for your help!

I'll loosen the reservoir cap first, to relieve any pressure, then screw it back on before removing the drain plug. Once it starts draining and I have me drain pan centered, I'll remove the reservoir cap and let it drain, which should pull a good amount of the coolant in the reservoir out. If there's some still in it when you finish draining, I wouldn't worry about it. You're never going to get all of the coolant out of the system. The radiator cap is not a vent cap; if you look at it, you'll notice there's no spring under it. It's sole purpose is to allow you to fill it with coolant (unless you have the "special tool," which I actually have, but I never found a need to use it on the R51.

I fill the reservoir to the "MAX" line when I first start it because there's inevitably will be some air pockets in the coolant system until they are pushed out and into the reservoir. The reservoir is essentially an expansion tank, so the level will constantly change as the engine is running. Best time to check is before the first start of the day, when the engine is cold. If the level is a little above the "MAX" line, it's not going to matter. If it is overfilled, the excess coolant will be pushed through the vent in the reservoir cap to the drain hose where it will end up on the ground. Obviously, we prefer for this to not happen.

Just wanted to say thanks. It was almost too easy – I have no idea why the tool is needed.

The coolant was draining for a long time, a little over 6 quarts total. I used my Lisle funnel to fill the radiator, closed it, filled the reservoir to the MAX line, closed it. Turned the engine on without raising the front – I figured I could always do that later if any problems arise. Heat worked fine front and back. Took it for the drive, no problem. Checked the level next morning when cold – exactly at the MAX line.

It almost looks like draining and filling the coolant on this system is easier compared to the traditional system, unless I am completely missing something. So thanks again for providing directions, it’s actually the easiest fluid change on this vehicle.

I'm just about to do total flush of engine coolant, having it cleaned with flush aditive first.
But I am a bit skeptical about being able to flush it entirely.

Service manual says 9-12 quarts of coolant total and if you take into account that reservoir tank holds about 3/4 and you managed to drain approx. 6 quarts....this means that 2-5 quarts were left in the system after draining via drain plug.

So, if I use flushing agent to clean it entirely, 2-5 quarts of flushing agent will remain in system after flush and drain. Each subsequent drain and refill will dilute it down significantly, but in theory I will never get rid of flushing agent 100%.
So I am thinking about doing:
- drain first
- then flush front and rear cabin heater with garden hose
- then add chemical flushing agent
- drain and flush both cabin radiators again, including engine cooler
- repeat everything with fresh distilled water
- dring finally and only then fill it with fresh BLUE (or GREEN) coolant

Thoughts?

You shouldn't need a flush additive unless there is rust in the system, and if there is, you have bigger problems. If you use tap water, then you are also adding minerals into the coolant system, which isn't good. My recommendation is to just drain and fill. If you are using Nissan Blue, it is already pre-mixed and will be compatible with the green coolant left in the system. If you are using Nissan green or aftermarket green concentrate, then use distilled water which you can get at Walmart or any drug store for about $1/gallon.

Well, as I do not have rust nor any visible dirt in cooling system, my only consideration for flushing the system is to prevent coolant/ATF cross contamination. With other words, to prevent possible leaks in main radiator.

Flushing it is not going to prevent the cooler leak issue. The reason for the radiator failures on R51's is because of a seal that fails on the internal cooler on a number of Calsonic-made, factory installed radiators that were installed from 2005-2010. It was a manufacturer's defect, not a maintenance issue, that caused the failures.

Looking at the service manual I see that there are 4 drain plugs on the block itself to drain the coolant. Does anyone have any close up pics of these?

I cant see them from underneath. Over at the frontier forums it was said that both front wheels had to be removed to access the drain plugs. I haven't had time to get em off and get in to look but if anyone has pics that'd help. I'm wondering mainly if their hex head bolt plugs or regular bolts.

Thanks

Did my first coolant drain/fill since I bought it w/33k mi on it. I was really dreading it but it was very easy. I didn't ramp up the rpms as noted above I just started, let idle, ran front/rear heat at max until engine was at operating temp (man you could roast a chicken in that cab), then topped off. Not sure there was even hardly any air in it, didn't have to add much at all.

Did lots of research on the board here before I undertook this so thanks to all who posted.