Drain and fill radiator?

[Computron]

Ok call me stupid... I’ve had my 2004 NSX for over 3 years now and I never noticed that the radiator has no cap on it. I don’t want to mess with all the different drain points and just want to do a simple drain and fill of the radiator.

How do you do this on the NSX? Is the tank in the engine bay more than just an overflow tank like other cars? Do I fill there? Not sure after I drain the radiator where to fill with coolant. Seems like it would take a while to fill the radiator via that tank instead of direct in the radiator.

any advice for what I want to do?

 

[Old Guy]

Yes - from the back end and it does take a while.

Pretty hard to drain 'just the radiator' if you think about it. If you drain the radiator, the lower rad hose is going to keep filling the radiator from the 'rest' of the system. You could try clamping off the rad hoses and removing them from the rad to drain just the rad; but, what's the point. You end up with a mix of new and old coolant which really leaves you nowhere in terms of restoring the anti corrosion properties to new and you probably need to do the full meal deal burp after because of the risk of trapped air. I suggest you follow the drain procedure in the service manual. The Wiki has some good suggestions about draining and burping the system including, as I recall, some spare bits in case you damage the seals on the drain cocks.

Edit - The NSX Wiki does not have a section covering coolant replacement. It must have been a DIY post that I read.

 

[goldNSX]

Seems like it would take a while to fill the radiator via that tank instead of direct in the radiator.

Yes which involves getting all the air out of the system again.

Why flushing the radiator only? There are about 1-1.5 gallons in the rad while the whole system has around 4.

 

[Computron]

Yes which involves getting all the air out of the system again.

Why flushing the radiator only? There are about 1-1.5 gallons in the rad while the whole system has around 4.

I was trying to keep things simple. So I guess there is no simple with the nsx?

For my other Hondas, just draining and refilling the radiator gets most of the coolant out... I ignore the block drain because it’s so hard to get to and makes a mess. Sometimes I just drain and refill twice. Guess I can’t easily do this with the nsx because of the rear engine front radiator design?

 

[Honcho]

I was trying to keep things simple. So I guess there is no simple with the nsx?

For my other Hondas, just draining and refilling the radiator gets most of the coolant out... I ignore the block drain because it’s so hard to get to and makes a mess. Sometimes I just drain and refill twice. Guess I can’t easily do this with the nsx because of the rear engine front radiator design?

As [MENTION=10201]goldNSX[/MENTION] said, there is more coolant in the hoses and engine block than there is in the rad. The Front-Rear design of the system means you have to drain and fill as a system because air and coolant can become trapped in different sections. Just follow the service manual method (pages 10-5 to 10-7) and you will be fine. A few tips:

1. Before draining, set the climate control to max temp. This will open the heater core water valve and make sure you are able to fully drain and fill it.
2. When bleeding the system, get the rear end of the car as high as possible. This will encourage any trapped air bubbles under the car to work their way to the rear bleed screws and/or header tank.

The pros (e.g., LarryB, Kaz, etc.) use a variation of this:

https://www.amazon.com/dp/B0787JQSFH/ref=sspa_dk_detail_0?psc=1&pd_rd_i=B0787JQSFH&pf_rd_m=ATVPDKIKX0DER&pf_rd_p=a54d13fc-b8a1-4ce8-b285-d77489a09cf6&pf_rd_r=FHSFRYDRBXB0DPC34HDN&pd_rd_wg=ErYa3&pf_rd_s=desktop-dp-sims&pf_rd_t=40701&pd_rd_w=oMUk3&pf_rd_i=desktop-dp-sims&pd_rd_r=88683cba-aebb-11e8-ad5d-f9d1f1abea37

It pretty much eliminates the possibility of trapped air in the system and lets you test the dry system for leaks before filling. IIRC, Larry uses the vacuum fill and then runs the car for a bit with the cap off to burp out any air. Kaz also uses the vacuum fill, but then follows the manual bleed procedure. Both of those guys have done this on literally hundreds of NSXs, so I think it is more a style choice than anything. If you plan on keeping your NSX for a long period of time, I recommend picking up a vacuum fill tool- it makes the coolant changes so much easier.

 

[Computron]

As @goldNSX said, there is more coolant in the hoses and engine block than there is in the rad. The Front-Rear design of the system means you have to drain and fill as a system because air and coolant can become trapped in different sections. Just follow the service manual method (pages 10-5 to 10-7) and you will be fine. A few tips:

1. Before draining, set the climate control to max temp. This will open the heater core water valve and make sure you are able to fully drain and fill it.
2. When bleeding the system, get the rear end of the car as high as possible. This will encourage any trapped air bubbles under the car to work their way to the rear bleed screws and/or header tank.

The pros (e.g., LarryB, Kaz, etc.) use a variation of this:

https://www.amazon.com/dp/B0787JQSF...&pd_rd_r=88683cba-aebb-11e8-ad5d-f9d1f1abea37

It pretty much eliminates the possibility of trapped air in the system and lets you test the dry system for leaks before filling. IIRC, Larry uses the vacuum fill and then runs the car for a bit with the cap off to burp out any air. Kaz also uses the vacuum fill, but then follows the manual bleed procedure. Both of those guys have done this on literally hundreds of NSXs, so I think it is more a style choice than anything. If you plan on keeping your NSX for a long period of time, I recommend picking up a vacuum fill tool- it makes the coolant changes so much easier.

That vacuum tool looks cool. Can someone explain how that works? What steps from the service manual method can I eliminate with this tool? If it will save me from making a mess, then it's totally worth it in my book!

 

[Honcho]

That vacuum tool looks cool. Can someone explain how that works? What steps from the service manual method can I eliminate with this tool? If it will save me from making a mess, then it's totally worth it in my book!

Not that hard.

1. Drain system.
2. Tighten everything back up.
3. Connect vacuum tool to fill neck and pull vacuum until hoses compress fully.
4. Wait at least 60 minutes and see if vacuum gauge moved. If it did, you have a leak somewhere. Go find it.
5. Fill clean 5 gallon bucket with Honda coolant and drop fill line into it.
6. Open fill valve and watch coolant get sucked into the system. Close valve once fill level is where you want it.

 

[Old Guy]

That vacuum tool looks cool. Can someone explain how that works? What steps from the service manual method can I eliminate with this tool? If it will save me from making a mess, then it's totally worth it in my book!

The vacuum refill tools are nice. Just be aware that you also need a reasonably sized air compressor to pull the vacuum. A portable compressor for an air nailer probably is not going to make the cut.

There are a number of Youtube videos touting different versions of the product. Just Google Engine Cooling System Vacuum Refill

 

[Computron]

Not that hard.

1. Drain system.
2. Tighten everything back up.
3. Connect vacuum tool to fill neck and pull vacuum until hoses compress fully.
4. Wait at least 60 minutes and see if vacuum gauge moved. If it did, you have a leak somewhere. Go find it.
5. Fill clean 5 gallon bucket with Honda coolant and drop fill line into it.
6. Open fill valve and watch coolant get sucked into the system. Close valve once fill level is where you want it.

When I drain the system, do I not have to worry about the coolant trapped in the block or low lying hoses? Does the vacuum suck the rest of the coolant out when it runs? Not quite understanding how the vacuum will remove the last of the coolant if I have everything tightened back up before running the vacuum?

 

[Old Guy]

The vacuum refill system is a refill only tool. Its primary benefit is that it greatly speeds the refilling process and reduces the risk of an air pocket in the cooling system. On the NSX, doing the burp to get the air out of the system is tedious, even with the back end elevated.

You still need to drain the cooling system the difficult way - using all the drain plugs in the system. If you look at the routing of the coolant lines, the lines actually go up slightly coming out of the engine, and then down along the rear bulkhead and then under the car and then I recall that the lower rad line actually goes up slightly before it connects to the bottom of the rad. Net result is that the bottom of the rad is not the lowest point in the cooling system. If you open the rad drain or remove the lower rad hose, because of the way that the coolant lines are connected to the engine you likely will get none of the coolant out of the engine block and most or all of the coolant in the under car pipes will also fail to drain. In addition to the rad drain there are two drains on the under car pipes and two block drains (I think that is all). They all need to be opened.

In order to drain the system, you really need a hoist to get under the car or be prepared to remove all 4 wheels and get the car up on jack stands so that you can get under the car to access the drains on the coolant pipes and the engine. I don't have a hoist so I did the jackstand thing - once. No more. This is one of those tedious activities that this old guy is happy to have the dealership do. I suggest you do the same.

 

[goldNSX]

This is one of those tedious activities that this old guy is happy to have the dealership do.

...if they know what they're doing...

 

[Albert86]

Well you have 1 of 197 cars ever produced for the US market with a 2004.
I sure wish I had your problem.
I think you should heed advice and try to either do the procedure as as the manual describes, or get some help that can work with you to do it.
Air in the lines can cause over heating and possible engine damage.
Let's keep your 04 on the road.

 

[Computron]

...if they know what they're doing...

Exactly! This is precisely why I am looking into doing more maintenance myself. I have a friend who works at a dealer and he’s been telling me about behind the scenes things that the service shops do even at a dealer when it comes to fluid changes. Like just replacing brake fluid in the visible master cylinder container only instead of bleeding through the system.. changing coolant by just draining and refilling the radiator without draining the engine block... etc. I’m just thinking whether they would even know what to do with an NSX and I doubt they’d take the time to research it and do it right.

i wouldn’t mind paying to have it done if it was done carefully and properly. But that’s hard to guarantee unless you personally know the mechanic.

 

[Old Guy]

Then its time to get a service manual.

 

[Larry Bastanza]

As mentioned above you will need to use all the drain plugs, radiator, engine block, and center drains in the tubes under the seats(outside above the plastic cover mid-body). Also make sure the heater valve is OPEN. If you are not using a vacuum refill tool, it is important to raise the car in the rear, so the radiator is lower then the engine block. Open all bleeders (radiator, heater valve, engine block(2). Fill and as they bleed fluid close them. Once completed go for a drive, watch your temp gauge. Up to full temp, run the heat for a few minutes, until heat is coming out of the system. Return home, then wait some time to cool, and check the reservoir. Typically another quart or so will need to be added.

HTH,
LarryB

 

[051009]

Is the tank in the engine bay more than just an overflow tank like other cars?

I've wondered this question too if anyone has any info that would help it would be appreciated. The answer must be yes as the reservoir tank cap is a pressurized one whereas a "normal" overflow tank is basically at atmospheric pressure (and can be opened at any time to check levels).

Is the NSX tank dual chambered or anything of the sort?

 

[mwagner10702]

Is the NSX tank dual chambered or anything of the sort?

Nope.

 

[Larry Bastanza]

The tank is directly part of the system. "Full" is over halfway full. It has a full marker on the side.

HTH,
LarryB

 

[Computron]

Ok, so does that mean the NSX has no overflow tank then like other cars?

 

[Honcho]

Ok, so does that mean the NSX has no overflow tank then like other cars?

The tank is pressurized and has 6 separate chambers designed to remove air from the system as well as prevent sloshing. It is an "overflow" tank in the sense that it is designed to catch boiling-over coolant and remove the air, but it does also regulate the coolant level in the system. Circulating coolant is returned to the tank via the top hose, where it migrates to the bottom of the tank (leaving any air at the top) and then works its way through the 6 chambers until it is ready to be drawn from the tank via the bottom hose, if needed. This is why you need to run the car with the cap at the half-tight position after opening the cooling system- this allows any trapped air at the top of the tank to be vented out. As Larry mentioned, you will need to top off the tank after this step.

If you really want to see the tank in detail, you can read Kaz's post here. Kaz is one of the engineers at Honda who designed the NSX. We are lucky to have him as a resource for these type of things.

*edit* If you really, really want to understand the system, read this.

 

[warrenw]

I have replaced my entire coolant three times. Once just for maintenance after buying the car, then when I did the timing belt, then once more when I replaced all the hoses.
The bleeding procedure in the manual works perfect, just as described. The only thing I add is to get the rear end of the car up in the air.
Yes, cap half open to start, but the service manual says to just add fluid after the car cools.

Here is a hint. When you open the bleed valves on the radiator, replace the o-rings on those valves first. They always will have flattened.

 

[Mac Attack]

I have the vacuum tool but I would only use it to refill the system after replacing all of the coolant hoses. It FLATTENS the hoses and will likely cause damage if the hoses aren't in new condition.

This is what I have used on the NSX and others:
https://www.amazon.com/gp/product/B00804HWOU/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

However, the coolant drain/fill procedure described in the owners manual works fine too. Just follow the procedure on here recommended by others to raise the rear end as high as you can.

Warrenw also has good advice: Buy the radiator o-rings (two of them) in advance, as well as the aluminum crush washers for the coolant pipe drains in the middle tunnel of the car (two or three).

I recommend you invite a fellow NSX owner over to help if possible for your first time doing this. And follow the service manual.