Hi Guys,

Yesterday, I replaced my coolant, thermostat and upper/lower radiator hoses on my 2013 G37S Sedan, so I wanted to share some tips that helped me during the process. Note that the car is just under 67K miles now and 2015/20K miles was the last time the coolant was drained and filled by the dealer; At that time, the car was at the 2 year mark and the dealer replaced the green "replace every 2 years" coolant with the blue "long life" coolant. To reach the decision to change "early", I used which showed that the existing "long-life" coolant was leaning towards being acidic with less desirable boil/freeze points. As such, I decided to be proactive since it had been 7 years since the last drain and fill.

I had initally thought about using the dealer for this service, but I enjoy doing the work myself because in addition to learning, it also allows me to clean/inspect areas of the engine bay (and underside) that are normally unreachable (i.e. the coolant resevoir itself, area below the driver's side airbox, etc.). I also like saving roughly $400 on parts and labor as below is what the dealer quoted (below).

-Radiator: $198 for drain and fill, recommended by Infiniti at 105K miles (he wasn’t sure why mine was done at 20K, but I mention above that I initially had the green coolant)
-But then they recommended replacing the Radiator Hoses: Hoses with new clamps, $110 for parts and $430 labor (Includes drain and fill)
-They also recommended thermostat replacement: $155 (parts and labor)
-They did not recommend O-rings for drain plugs (even though the FSM recommends replacing both)
-Around $600 out the door with tax

Here's the receipt from Z1 for the parts I purchased for the DIY (there was Black Friday promo at the time that saved me $9):


First off, for the coolant drain and fill Eugene's DIY here is by far the best one I found online:
Some things to add to his DIY:
1. I didn't end up changing my upper and lower relief plug and drain plug o-rings. I did order the lower drain plug o-ring from Z1, but they sent the wrong part (looked like a gasket for something else). I called around and nobody had the o-rings in stock till Tuesday of next week, so I went ahead and used my existing ones that actually looked fine (recall from above that the dealer didn't recommend replacing). I inserted the PNs below for both that I found buried in another thread.

21416-48A00
O-ring for upper air relief plug

21441-5V000:
O-ring for lower drain plug

2.
In the video, he says to wait for the thermostat to open as indicated by a warm lower radiator hose. Note that I left the car running for 15-20 minutes before sensing anything resembling warmth on the hose and was convinced it would never open and that my new thermostat was bad. But then it happened. One thing I found in another thread that helped is to run the heater at 90 degrees with the fan at max. You will know that the termostat opens because the level in your spill proof funnel (I used

this one from Lisle

this one from Lisle

, Red Fitting in the radiator opening with the associated cap) will drop and you will need to pour (slowly) a little more fluid in the funnel.

3.
When you pour the fluid in the radiator throught he funnel, do it very slowly (FSM actually has a spec for how slow) as you do not want to introduce alot of air. Also, be patient and wait for the air to escape (you will see the burping/bubbles). I waited 20 minutes till I did not see any form of bubbles in the funnel. The web is full of 370Z/G37 owners that had problems in this area. Patience is key as our coolant systems are notorious for trapping air that causes a host of issues (the dealer even warned me against a DIY because of the problems they see when others try the DIY then bring to the dealer to fix). With the Spill Free funnel and some patience, you'll be fine.

4.
Once the bubbles are gone, close everything up and go for a 10-15 minute drive. When you return, top off the coolant resevoir to just below the max line and check for leaks. Jack the car back up and reinstall the undershroud; I know it's a pain to install the undershroud at this time vs. when the car was on stands prior, but I like the visibility to leaks provided when the undersround is removed.

That's additional feedback on the coolant drain and fill portion, but recall that I also changed hoses and the thermostat and wanted to provide some lessons learned on those items as well.

1.
Hoses. The existing ones had been on the car nearly 10 years and did no want to come off easily. I found that it's better to tug/pry on the engine side to break the hose loose. I tried a hanger/metal rod (someone on YouTube recommended), but the hanger/rod bent too easily. Instead, I found that a thin screwdriver worked best. Pull the hose (engine side) while gently prying with the screwdriver and you will feel it break loose. Once the engine end is off, it's easy to get the radiator side (top inlet is plastic, be gentle) free because you can now gently wiggle/twist the hose to break it free. Laying under the car helps with the lower hose as it's tough to get to from the top. Also, I had some corrosion on my fittings, so I used 600 grit wet sand paper to remove most of it. No hose grease for me.

2.
Thermostat. The thermostat is somewhat buried, so the removal and install requires some forethought as there isn't much to work off of on the web. I'd advise against using impact tools as the bolts were not that tight and using a small socket helps you feel around and find the right bolts (which again are not that tight, despite what you will find on the web). Note that there is an electrical connector for one of the Cam Position sensors (don't remove/unbolt the sensor like some online say, that's not needed) that's in the way; if you shine your flashlight into the connector, you will see that there is a small clip that needs to be pried (again, gently) with your thin screwdriver while pulling; the clip will slip right off. Once off, I used a small 10mm ratchet as the bolts themselves. 18 ft/lbs is the torque spec, but good luck getting a torque wrench in that area (I tightened by hand as I'm familiar with the force needed for 18 ft/lbs). When you place the new thermostat in place, be careful not to skew the gasket while you are trying to get the bolts threaded it's difficult to see where the bolts go, so you need to "feel" while holding the thermostat and gasket in place. There is a little tab on the gasket that can help guide you. I also used my phone to snap a pic (below) just to make sure everything was lined up (note the tab on the gasket).



That's all I have for now. Hope this helps.

Mike

 

Did this today. Quick and easy till I got around to replacing the hose adapter by the heater core. I watched the Z1 motorsports video but it was on a 350Z and the hose was longer allowing it to be pulled above the engine to work on it. Our sedan uses a very short hose. As soon as I pulled it off the heater core and started raising it up to get a look at it, the adapter broke. Came out in hundreds of pieces. An hour and a half job turned into roughly 4 hours all together because of it. If anyone reading hasn't replaced their adapter/bleed port-DO SO NOW. It is really a ticking time bomb.

 

I considered changing mine as well, but it still looks new and I didn't want to create a problem where one doesn't exist. I do check the coupling for seepage weekly when I wash the car as I know this has been an issue for many. Any idea why that coupler is needed there in the first place? Seems that extending the hose a little further would have been a better idea, but maybe the coupler was added to make the heater core connection more serviceable?

 

While I agree with the premise of "if it ain't broke, don't fix it," I am also a firm believer in "a ounce of prevention is worth a pound of cure." This is one of those items that should be addressed BEFORE it becomes a problem. When it fails, it will be at the most inconvenient time and under the least ideal of conditions. This plastic piece is literally a ticking time bomb as many have stated.

I used a brass fitting (personal choice), but any ¾" metal barbed fitting should work just fine.

As for why the coupling is used in the first place ¯\_(ツ)_/¯

 

Finally getting around to a coolant flush due to age. Outside of new hoses, thermostat & gasket, anything else I should consider?

 

I also replaced the OEM Spring Clamps, but suspect they are already on your shopping list, as is replacement of the plastic heater hose connector (if not already replaced) and acquisition of a spill free funnel.

This is a very satisfying job to perform DIY.