Coolant tank pressure (possible buy)

[Burny]

Hello all,

I'm Nico from Belgium. 33 years old and a long time Honda driver.
The time has come to find a good NSX.
So yesterday i went to inspect one! A '91 manual.The car was in good condition, everything looked and felt good.
Except for 2 things:

5 tot 10 minutes after a spirited drive, i noticed the coolant tank was slowly releasing pressure through the cap.
Just a little stream with a high pitched tone, but i assume it had been releasing that pressure for 5 tot 10 minutes, maybe more.
Is this normal?

Both the radio and climate control were completely dead.
The owner insisted that this was because when he changed the battery, there was a spark.
So he's sure it's just a blown fuse. But the little fuses all checked out ok. Could it be one of the bigger fuses?
Or is there another component/wire that those 2 things have in common, which could cause this problem?

Thanks for reading.


---------------
Additional info:

Additional info:


Both the radio and A/C control were completely dead.
So whatever buttons i pushed and turned, nothing happend. The displays remained dead.
So it does sound plausible there is a problem with the powersupply for both units?

I'm also pretty sure the A/C circuitry needs a repair.
The seller told me, when the A/C still worked (so before the battery-spark incident) the A/C would only work on maximum or not at all.

As for the second question: the temp gauge remained steady just a little bit under 'halfway'.
No fluctuations, it took about 5 minutes to warm up.
Bottom of the car was dry, no leak spot on the floor where it was parked.
However there was a tiny bit of coolant on the rim of the tank, before the drive. Not after the drive.
After the drive it was completely dry.
Coolant level was in the middle between high and low.
Both coolant and oil looked normal. If it would be a defective head gasket, i assume i would see something in the coolant, or oil? Or white smoke from the exhaust.

The seller has invoices for timing belt and waterpump replacement, done 3,5 years ago.

[hugabuga]

You have PM

Water tank tends to crack with age, there should be no steam nor liquid leaks released from a good water tank.
HP amplifiers and A/C controler are the weak electronic components and usually fail is just a question of when, but you can ship them to USA to get them repaired at affordable prices.
Replacing the battery will not damage them as they will only be powered when you turn the key and start the car

Finally if it's a 91 model make sure the gearbox serial number is out of the snap ring failure range, or use it as an argument to lower its price: http://www.nsxprime.com/FAQ/Troubleshooting/transmission.htm

Good luck!

[Kaz-kzukNA1]

Hi, Nico. Welcome to the club.
It is my policy not to carry out pre-purchase inspection or comment on the specific NSX on the market to be fair with the seller as well as for the buyer unless there was wrong info involved so please take the following comments as a general information.


First, you may want to visit the 'Technical' section of this forum and check the thread in the 'Sticky' part at the top.
You will find lots of info there such as the one from Sudesh in 'NSX Refresh' thread that will show many items that may fail on our classic NSX.
Also, you can visit my 'NSX Technical and Service Information Index' and '..... Index 02' for technical story/fact/example.
You can also visit the 'NSX Build' forum and go through the thread 'Britludes NSX story' to learn what can be done on some of the items on our NSX.


Regarding the hissing sound from the coolant tank....
It depends on the pressure of the system.
The tank cap has a certain window to control the pressure of the cooling system and if it exceeds it, it will release the pressure especially during/after the spirited drive.
If you stop the engine and started the cooling period, the entire system will contract and now the cap will suck back the air several times for a few seconds.

From what you wrote, it sounded like tank cap failure but can't confirm without testing it.
One thing you can do is to check the colour of the cap.
If it was still using the brass coloured one, then that's super old because it was replaced with the black one ages ago. You must check and replace the tank cap regularly.

Just check the age of the coolant hoses as well.
You may be able to read the manufactured YY/MM/DD text on the hose itself.
After 10 years time, you never know when they will fail. You will have 21 – 25 hoses depending on the spec of NSX.

Please check the radiator as well.
It will start leaking from around the right bottom side near the lower coolant hose neck.


The CCU and Audio head unit are famous for the capacitor leakage inside and it will result in many failure modes including loss of power.
If the CCU only operated at max fan speed setting, then that's one of the most typical failure mode and won't be surprised to see further failure such as loss of power.
Audio head unit is the same.

For both items, you can visit the 'Blog' section of this site, click on any of the blog post and you will find blog category on the right side window.
You can check many examples in the category 'A/C CCU Board Service' and 'Audio'.


You can't judge the head gasket condition simply by the fact that the gauge stayed 'just little bit under halfway' or by looking at the 'colour of coolant and the oil'.

The head gasket on our NSX is very strong but it could show failure even when the gauge/coolant level/ colour/etc were perfectly fine under normal street driving conditions yet the gasket was already damaged and the issue only showed up when driven really hard.

You need to carry out the eng block test or use exh gas analyser at the header tank.


From your post on NSX Prime, it seems that you are aware of the snap ring failure.
However, many owners misunderstood some of the aspects of this issue.

The main point is that snap ring failure can happen on any NSX or even other Honda/Acura models using the same method of holding the counter shaft in the trans case.
It happened on other Honda models such as Civic, etc and also I know it happened on JDM NSX that doesn't even use J4A4 Gbox series that was stated in the TSB from Acura.
Though, it was very rare case as there are about 7,000 – 8,000 NSX in Japan and I only heard about a few cases. In Japan, we used J4A3 seriese due to different gear ratios, etc.

TSB was released because these J4A4 series gbox with that serial no. window had higher possibility of failure.

So, even the gbox was within this 'snap ring range', it didn't mean that all of them will fail and at the same time it didn't mean you were free from the snap ring failure if your gbox was out of this range although it would be super rare to fail.
I'm actually helping one JDM NSX owner with possible snap ring failure at the moment.


By now, most of the early model NSX would have covered a certain mileage so you can do quick check to see whether you are very likely to have snap ring failure in the near future or not.
The 1st and 2nd drive gears (and Reverse gear as well) are directly cut on the main shaft body and the shift fork for these gears are located on the counter shaft side.

So, at low speed, drive NSX in 1st or 2nd gear and press On and Off at the TH pedal rapidly to cause jerky movement many times. During this process, just touch the top of the shift knob with one finger.
If you can feel the shift knob vibrating massively or even move back and forth trying to pop out of the selected position, you may need to be prepared for the big surprise.
The excess movement of the counter shaft will push the 1-2 shift fork resulting in big vibration or even a movement at the shift lever.
Once it managed to smash the snap ring enough, it would pop out the gear when you were in 1st or 2nd gear.


By now, I think everyone knows that 'snap ring failure' is in fact the 'trans case issue' and nothing wrong with the snap ring itself but it will be smashed in pieces.
You will need to replace the trans case to fix this issue.


Good luck with the hunt.

Kaz

[Burny]

@ hugabuga: Thanks for the offer&info. Coolant tank and cap will be replaced in case i should decide to buy this car.

@ Kaz: Wow, long read, thanks for making that effort.
The last couple of months i did alot of reading on the NSX and amongst other things, i have made a list of parts that i want to replace pre-emptive.
Coolant tank, caps, hoses, valve cover seals, fluids etc are on that list. I just thought it was weird to hear that pressure release. Never noticed it on my other Honda's.
Then again, i don't think i have ever opened the bonnet right after a spirited drive :)

I am indeed aware of the snap ring problem, but my thread on Prime might be confusing, since it's about 2 different NSX'es. The first one i went to see around 6 weeks ago, the second (last couple of posts) i saw last weekend.
In the end i decided not to buy that first one (too many problems, weird seller, etc) but this second one is alot more promising.
I carried out the snapring test exactly as you described it, there was no movement on the stick so i guess so far so good.
The gearbox of the second NSX is also not in snapring range.

I've been hunting for nearly 2 years now, saw over a dozen NSX'es, but all in all never really found one good enough.
That may be different with this last one.

I'll keep you guys up to date.