Radiator Leak Question.....

[uscarioca]

so I am getting a few coolant fluid drops to appear under my radiator. Under further inspection I located, what appears to be the source of the drops. Some sort of valve, on the radiator bottom side. Can anyone explain what this is? It's not not the drain plug. Do I have an issue here or do I just need to place a cap on this?

thanks!
Chris

 

[Old Guy]

As you note, that is clearly not the drain valve; but, is it located on the bottom of the boss that the drain valve screws in to? I don't have a lift so I can't get under my car to check.

If it is the boss that the drain valve screws in to, the drain valve may be leaking. It has been a bunch of years since I did this; but, my recollection is that when you release the drain valve the coolant pours out of that little hole. The drain valve has a seal on it and the seal may have failed.

1986-2020 Acura Gasket, Drain (Toyo) 19012-PD2-004 | OEM Parts Online

1986-2020 Acura Gasket, Drain (Toyo) 19012-PD2-004

acura.oempartsonline.com

 

[uscarioca]

a ha. makes sense. let me try replacing the drain valve here, did not realize this was all connected. Will let you know if this fixes things.

thanks

 

[Wild Turkey]

That looks like the outlet where the coolant drains if you open the lower petcock, (or if the petcock fails.)
Likely the petcock is OK - you just need an new O-ring as @Old Guy noted. Mine failed last year in the middle of Winter storage (top one, took a while to track back - key is fluid on top of the rad fan shroud.) I'd replace the top petcock o-ring as well if you're doing the bottom one.

@Old Guy part # was the same one I used last winter, which worked on my USDM but interestingly, amayama shows a different part number for RHD vehicles, 19012-PV0-005? Not sure where you are, but RHD gets a better rad?

Radiator for Honda NSX 1 generation 09.1990 - 11.2001 - Honda Car and Auto Spare Parts - Genuine Online Car Parts Catalogue - Amayama

Radiator for Honda NSX 1 generation 09.1990 - 11.2001. Buy OEM spare parts online. Low prices, proven reliability, fast shipping from Japan

www.amayama.com

 

[ralph cerbone]

my car would do this if it sat in garage during winter for a prolonged period , this year had car out every weekend , no leak . The o ring shrinks once you start driving it it should be fine . Just sit on it and see what happens once you start using , remember measure twice cut once .

 

[Wild Turkey]

Not sure if you're kidding or not, but that's not how o-rings work. An o-ring that shrinks would leak; o-ring rejuvenators (for swimming pool fittings) cause o-rings to swell a bit. o-rings are compressed between two surfaces, usually perpendicular to the direction of joining so that the sealing force is optimal and constant, independent of how much it is tightened. (This petcock, or valve as @Old Guy described, uses this design, with the sealing force from inside to outside the o-ring.) They often leak when a portion becomes compressed with a flat spot over time. Mine developed a crack and became a "c-ring", which leaked continuously but slowly. For o-rings, measure twice and cut never.

If you're wondering about it, if it feels dry or cracked, or you can detect a flat spot, replace it.

 

[Old Guy]

Interesting observations on the O rings. Being an old guy, I am becoming increasingly familiar with shrinking and swelling in all its manifestations. During the winter of 2021 - 2022, the radiator bleeder, the same one that tturkstra referred to, decided to have a release and left about a 40 mm puddle on the inside of the storage bag while the car was in storage. I pulled the car out of the storage area, let the engine idle to come up to temperature while I checked everything else and then I examined the bleeder for further leakage. It seemed tight so I drove home with a mental note to replace the seal on the bleeder.

I have a seal for the bleeder (part of the parts package for the coolant hose replacement); but, I never replaced it because the drip did not obviously reappear. However, I did note that the coolant level was dropping in the expansion tank requiring a top up of about 100 ml every 2-3 months so the leak is probably still there. Maybe I will get around to doing the hoses this year.

Absent some of that gooey rubber rejuvenator, I think it unlikely that the seal / O ring will restore itself by swelling. I suspect it might be a case that the seepage is incredibly slow and with warm weather dissipates before you see anything. I do know that if you unscrew a fitting that has been in the closed position for a long time the seal / O ring will have a relatively permanent deformation and it is unlikely that it will reseal following re installation.

For @uscarioca you might want to check the parts. I am not sure that the seal is included with the drain valve. If you order a new drain valve you might find that it still leaks if you try to reuse the original seal.

 

[ralph cerbone]

Not sure if you're kidding or not, but that's not how o-rings work. An o-ring that shrinks would leak; o-ring rejuvenators (for swimming pool fittings) cause o-rings to swell a bit. o-rings are compressed between two surfaces, usually perpendicular to the direction of joining so that the sealing force is optimal and constant, independent of how much it is tightened. (This petcock, or valve as @Old Guy described, uses this design, with the sealing force from inside to outside the o-ring.) They often leak when a portion becomes compressed with a flat spot over time. Mine developed a crack and became a "c-ring", which leaked continuously but slowly. For o-rings, measure twice and cut never. If you're wondering about it, if it feels dry or cracked, or you can detect a flat spot, replace it.

The point I was trying make was just dont start taking things a part ,the leak might stop when warm. All honda radiator drain plugs are face seated petcocks , the biggest problem is inexperienced guys over tighten them and damage the face seat . And yes I familiar with o rings ,dow corning o ring compound which causes them to swell . I used to service high pressure hydraulic systems (12000 psi )

 

[edvc520]

@Wild Turkey is a god sent.
So patient and helpful.

My 95 was experiencing some coolant dripping. I have then done my research on Prime, and I have messaged @Wild Turkey for help since he had experienced this according to this thread

He gave me some good advice as I have never touched a coolant system before.
He made it quite simple for me to follow, essentially:

- Got myself two new O rings.
- Release the top drain hole first, a little coolant will come out
- change the top petcock’s O ring first but keep it handy and don’t screw it back into the drain yet
- Release the bottom drain, coolant will rush out (way faster than I anticipated). Immediately plug the bottom drain with the top petcock. Still managed to lose like half a litre of coolant even though I have already prepared to plug it with the petcock
- now I can take my time to change the remaining O ring and screw it back to the top drain

 

[Wild Turkey]

You are too kind @edvc520 Didn't know you hadn't worked on the coolant system before. Note that any time the system is opened. You need to purge the system as outlined in the service manual. The NSX is too valuable take any chances with and a new motor will be hard to find now.

Glad this worked to fix your leak and you're smart to change both o-rings. If one is gone, the other won't be far behind. If you can get a friend to seal the top purge valve with their finger while you're changing the bottom one, the bottom one will drain more slowly.

Side note: while the other 3 purge valves are face seated, the upper (purge) and lower (drain) are interchangable hand petcocks that can be tightened by hand, as the o-ring seals radially, not on the face.