A/C refresh

[goldnsx]

My A/C still works but the evap is leaking. So one project this year 'could' be a complete refresh of the system.

Parts already here:
93+ evap
new Schrader valve inserts (eB China)
new A/C o-rings (R134a)
new dryer (R134a)

As it's leaking oil to a unknown degree it was always a wild guess of how much oil to be added every two years. So I'm going to flush the whole system with A/C chemical solvent and dry it with nitrogen 2.8. Anyone else did this procedure? New PAG 46 oil will be filled in the compressor directly.

One question about the suction and discharge hoses. They're out of production and have been very expensive. You get what you pay for. But what about the A/C hoses which can be found on eB in the US for $20-25. Or should I go a different route and ask an A/C shop (actually very hard to find here) to custom build me some based on the fittings and size of the old ones? Or should I just reuse my 30 years old ones?

[Kaz-kzukNA1]

Hi, goldnsx.

What was the original spec of your A/C system, R12 or R134a?

If it was R12 but retro-fitted to R134a, which parts were replaced for the conversion?
Honda/Acura supplied adaptor valves in the OEM retro-fitting kit tend to leak in longer term.


Answers to the above will change the amount of recommendation....

Kaz

[goldnsx]

Hi Kaz

Originally R12

2008
- Retrofit kit mounted
- 2 fittings R134a plus a can of oil

2012
- New R134a Denso compressor (replaced the loud unit before it failed)
- New o-rings R134a everywhere (except the ones of the expansion valve)
- New R134a receiver plus hardware
- New Schrader valves. Not Honda ones (only the complete line available at a crazy price tag), some of China I guess. The dealer had a set you can buy from eB. I've bought a full set years ago and they work pretty well on other cars.

No further R134a components.

My evap has been leaking since 20 years or so and it seems to be one of the bad batches the early cars came with. So I'll replace it with a R134a one. Changing the evap is a bunch of work, so I want to do it right.

I've found two R134a hoses in Japan for about $300 from Honda. Are they compatible with R12 hoses? Really needed to change them? I've found R134a hoses on RockAuto for $30 or 1/10 of the price Honda asks. Any good or better leave them.

https://www.rockauto.com/de/catalog/acura,1994,nsx,3.0l+v6,1000876,heat+&+air+conditioning,a/c+refrigerant+hose,6900

Thanks for any help in advance.

[Kaz-kzukNA1]

You may find some of the photos and process helpful through my AC Refresh blog.
Multiple posts and the 1st one starts here;
http://www.nsxcb.co.uk/entry.php?1836-AC-Refresh-01


Regarding the compressor oil….
I posted the same comment here or on NSX Prime a while ago but personally, for Denso compressor that came with ND-OIL8, I would stay with it rather than the PAG or POE.

This was the advice from the famous company where they refurbish all sorts of compressors back in Japan.

Unlike the modern electric compressor, the oil around the high speed rotating shaft of classic compressor can get in contact with the moisture and the outside air even with the presence of a seal.
ND-OIL8 has advantage in this area over other type of oil.

I normally get it in Japan through Toyota dealer as it's so much cheaper than Honda.
ND-OIL8, 250cc, parts no: 08885-09107
However, the description on the container is in Japanese so probably it is specific to Japan market that it's very expensive in other countries.

The R134a a/c system total oil amount is 160cc MIN and 180cc MAX so you want extra amount to cover several tasks.
You may want asking your local Toyota/Lexus dealer for the different part no. for at least 200cc of ND-OIL8 for European market.


The puncture of evapo is most likely caused by over-pressurising the system.
I experienced the same with mine.
I think it happened when I asked my local Honda garage to re-charge the system years ago despite they were using the expensive service station.
Having said this, almost all of the reported puncture cases happened at the lower pressure side of the evap after the exp valve so not sure of the actual cause.


With LHD model, aftermarket evapo is/was available.
With the OEM one (not sure LHD spec still available), the exp valve comes with it.
You should replace it at the time of refresh any way.


For flushing, you have several options.
Find the a/c specialist with the super-expensive a/c service station.
Ask them whether their service station/machine can perform automated flushing process or not.

They will disconnect the discharge/suction hoses from the compressor and connect their service station.
Some of them can flush the system in reverse direction as well if the exp valve needle was removed.
During the process, the old oil is removed from the system.
Almost all of the machine have separated container showing the colour and the amount of old oil removed.


If DIY, Four Seasons (or, 4seasons) Dura Flush is a good solvent.
It's non-flammable and was available for international shipping long time ago through Rockauto but not sure these days.
You should be able to find alternative one but be careful with the cheap ones on the auction sites.
With one product, it destroyed the heavy duty glove by just touching it even for a few minutes.


The DIY method is not as beautiful as the expensive a/c service station method but fortunately, our NSX uses ancient condenser design so can be done.

You can't flush through the exp valve so the needle pin must be removed if you want DIY flushing the evapo but as you are replacing it, not a problem.


Please inspect the two pipes located in front of the radiator.
The one between the dryer and the L-side condenser.
The other one connects the R & L condensers.

They take lots of abuse from stone, debris, etc.
Ideally, you want replacing them but please pay extra attention to the fittings at the condenser.

Even with the double wrench method, you could either strip the thread on the pipe on the condenser side or twist the fitting.
If it happens, you won't be able to make the tight seal and most likely being forced to replace the condenser itself by removing the front bumper or attempt the repair in that tight space.

Your nearby hydraulic shop may have short adaptor fitting/hose for repair purpose.


For the discharge/suction hoses, strictly speaking, R134a can escape through the R12 EPDM material. It can also attract moisture through the hose.
However, it's so minute that even when retro-fitting was carried out at the Honda service centre, the hoses were left un-changed.
As the ones from Rock Auto are R134a spec and so cheap, you may want replacing them anyway.
Just keep your old R12 spec hoses.
You can always go back if the new ones didn't work well.


Just one caution for you.
The thickness of the flange at both ends of the hose is much thicker with the R12 hose than the R134a one.
The chassis side fitting has the stud bolt and you will use the nut to attach the hose.
If replacing the hose to the R134a spec, just add multiple washers to get enough thickness so that you can use the existing nut.
You could try replacing the stud bolt to the shorter one but with the possibility of oxidation and limited space, you could introduce new issue.
For the other end of the hose where it connects to the compressor service plate, just use the R134a shorter bolt.
Obviously, you need two of them.


As you are going to replace the evapo, you will be forced to disassemble the heater unit.
Because of this, you may want replacing all of the EPT foam sealer inside there.
In fact, if you touch any of them, it may simply fall off in bits and pieces.
Same goes to the ones inside the blower motor unit.

If replaced, you will notice how much air was getting inside even when you set the CCU into re-circ mode.
No more smell from outside and you can even feel your eye getting very dry after refresh.

Can't remember the userID but Joe based in US has the EPT foam sealer refurbishment kit.
I bought a kit for another owner.

Must go back working now.

Kaz

[goldnsx]

Thank you very much for your extended post and valuable informations.

Oil
Denso ND-OIL8 (part no. 9990101) can be found at RockAuto: https://www.rockauto.com/en/parts/denso,9990101,a/c+refrigerant+oil,6928

Find the a/c specialist with the super-expensive a/c service station
The common problem: in the event of an A/C failure the dealers claim that they have to change the complete system (more profit, less risk). So flushing is not very common (no incentive either). The smaller shops I usually go to (one man shows) are very competent and are willing to work with you on a solution but they can't justify a super-expensive flush station. A/C spectialists with such a machine are hard to find and expect you to hand over the keys and pay whatever they want. So it's better DIY.

Flushing agent
Thanks for the hint. RockAuto does carry 4Seasons but not in stock. I'd prefer a non-flammable liquid over SuperCool.
https://www.rockauto.com/de/tools/heat+&+air+conditioning,fluid+/+chemical,a/c+system+flush,13621

Two pipes located in front of the radiator
They still look fine. Not much highway driving.
I've had no problem with the fitting or corroded aluminium 8 years ago, so it should be ok.

Suction/recharge hose
At their price tag on RockAuto I'm giving them a try.
Thanks for the hint on the fitting flange.

EPT foam
The foam attracts bacteria. Not sure if I'm going to replace it with the same type of material. That will be puzzle task whenever I see what and how is seals.

Two more questions
- How many quarts of flush agent are needed? I intend to flush each part three times, condenser many more. 2 quarts sufficient?
- How long have the components to be dried? I'm using nitrogen 2.8 but for how long?

Thanks very much again.

Now, have to order and wait for parts...

[Kaz-kzukNA1]

Depends on how far your system was contaminated previously or whether the leak detection dye was used in the past or not.
2 cans of Dura Flush should be enough because you are not flushing the evapo.
I prefer not using the dye but that's just me based on what I experienced in the past.


Unless you are using the industrial nitrogen dryer in closed loop condition, there is no need using the nitrogen for drying
as long as you have completely recovered all R134a refrigerant (danger of fire/explosion under pressurised condition) and flushed through the system.

Even if you used dry nitrogen, when passing through the narrow tube with the other end opened, it will cause condensation at both the internal and external surface
depending on the surrounding environment condition so I would normally just use the compressed air.


With the a/c pipe, just a few minutes is enough to push out any remaining flushing agent.

For R & L condensers, I normally check the other end of the attached clear tube and feel for any residue and repeat the process multiple times
as I don't have huge compressor tank.
Never measured the total time but with two condensers, probably like at least 30min.

Nitrogen is much more useful for pressure leak testing and for the 2nd stage vacuum drying process.
That's what used when installing the a/c for the home and small offices when back in Japan.


It depends on the performance of your vacuum pump but I have ancient 2 stage 15micron vacuum pump with dedicated vacuum gauge.
With this, for automotive a/c system, I normally pull vacuum for 15min and then carry out the leak check.
Then, move onto the vacuum drying stage.

Before this stage, some people charge the system with Nitrogen for pressure leak check as well as to improve the drying performance.

For the vacuum drying process, I normally run the pump for minimum of 2Hrs.

Kaz

[goldnsx]

Thanks again, Kaz.

Leak detection dye has been used in the past by an 'uncertain' amount. I won't fill it this time. Unless we have another unusual leak next time (in about 2 years).

The idea behind the nitrogen was to complete the system at home (except the receiver) and have as less moisture in the system as possible (or to remove the shop air in the lines) to speed up the vacuum at the filling station of the shop. I know that if the system is clean, moisture can't form harmfull acids. I don't have a vacuum pump yet. If you say a pump might be the better way to get wrid of the moisture I might consider buying one.

One note just read in a forum: A vacumm pump can only remove the vapor state substances so dry nitrogen is used to push out noncondensable contaminants from within the system.

[duncan]

As a more agricultural work-round: buy a male dash 6 and dash 8 hydraulic fittings from a local hydraulic pipework supplier, say £5 each, remove the tapered lead-ins and then put a longitudinal slot in the threaded section. These then can be used as DIY die/ thread chasers on the retained nuts on the two hard line cross over pipes. Doing so will clean and protect the threads on the condensors from galling prior to re-assembly.

[Kaz-kzukNA1]

Hi, goldnsx.
If the aim is to complete the system at your place AND eliminate the moisture in the system AND minimise the time being spent at the shop for charging the refrigerant, then just hire a decent vacuum pump.

You can buy one but may not be cost effective unless you use it regularly.

On the other hand, even the reasonably priced manifold gauge would become handy just for monitoring the system pressure to spot any issues.

I'm quite sure you are aware of the saturation curve of the water but unless you can use dry nitrogen in closed loop industrial system, just passing it through the system won't be enough to remove the moisture even on the automotive a/c system.

As soon as you expose the parts to the atmosphere, the moisture is introduced.

With DIY flushing, you rely on the flushing solvent to soak into the debris in a hope to separate it from the internal surface.
Once soaked for a while, then you run the pressurised fast flow of solvent fluid to push it out, ideally in reverse direction as well (back flush).
Then, the compressed air (or nitrogen in your case) to further push out any remaining debris.

I don't know what benefit the dry nitrogen has over the compressed air during the above process on automotive a/c system but if you already have access to it, it won't harm.
For small refrigeration system service, I do use nitrogen but for different purpose.

The vacuum pump will lower the boiling point and evaporate the moisture inside the system.
By keeping the pump running for long period, the saturated moisture will be removed further.

Once installed all new parts and confirmed that there is no leak with the system, I normally run the vacuum pump for more than 2Hrs.

When dealing with the service of small refrigeration system, even just 5g of moisture inside the pipe takes ages for removal.
However, with properly flushed NSX a/c system, good vacuum pump kept running over 2Hr would be enough.

So, after flushing the system, start re-installing the parts and install compressor and the receiver/dryer as the last item to be installed.
Carry out leak check and then pull deep vacuum for long period.
After hours, stop the pump but keep the system under vacuum in preparation for charging the refrigerant.

I'm HVAC certified in Japan but don't know how to convert it into F-gas certificate in Europe so can't handle the refrigerant.
I just ask my friend to charge the refrigerant at my place.

For your case, just keep the system under deep vacuum and disable the compressor (not required because of triple pressure sw but as a pre-caution).
Then, just drive to the nearby a/c shop to charge the refrigerant.

This will save everyone's time.

Kaz

[goldnsx]

If the aim is to complete the system at your place AND eliminate the moisture in the system AND minimise the time being spent at the shop for charging the refrigerant, then just hire a decent vacuum pump.
Hi Kaz

That's pretty much my goal (save time at the service shop). So I'm convinced to buy a vacuum pump and gauges/hoses instead of the nitrogen kit. At least I've found a supplier with reasonable prices (hard to find here).

Thanks very much and best regards