welding over the koyo radiator fill
 

I'm thinking about chopping off the radiator filler neck on my Koyo n flow and welding a piece of aluminum over it. it bothers me, does it bother anyone else? I was just looking at purchasing a radiator cap for it when I thought about this. I don't care for polished aluminum, I rather have my radiator unpolished if there was an option

So the issue here is one that I ran in to recently. Your N-flow has the fill port with the overflow tube attached to it. If you eliminate the overflow, you'll have no place for the expanded coolant to go, and subsequently return when cooled.

So what I did to mitigate the issue was to drill a small passage under the fill cap on the thermostat housing, tap it, then thread in a small barb fitting to go to the overflow tank.

The other option is to get a pressurized overflow tank from another vehicle and make it the highest point in the system.

I forgot to mention i have a s4 with the fill on the upper house with the overflow already there.

I was going to connect the 2 overflow with a "y" fitting

you can get a Thermo neck "plastic piece" that has NO Overflow nipple and run a flat cap.(mazdatrix)
That way your rad With the overflow tube is the only area that has a spring loaded cap.

I was looking at that also, but it looks like I would have to cap off the nipple that goes to the overflow. The most reliable way i know of capping those off is with a small piece of hose with a bolt clamped on it, Which looks real ghetto. Those vacuum caps aren't very reliable
wait, It's there a cap that would hold pressure so i don't need to cap the overflow nipple?

Got a link?

15-17Y0-N323
Radiators, Caps, Water Level Sensor

Are you talking about eliminating the long fill tube? Dont they sell the radiator that way now as an option?

Ah, maybe I'll do that., only run spring loaded at the radiator.

Rob, I'm not sure, but i Would have bought it like that if i would have known

Why not put a higher pressure cap on the neck your not using and then vacuum cap that overflow or just drain to the ground? It will probably never open anyway.

I'm thinking this well be a nice option also because buying the filler neck and cap that only holds pressure, plus o ring is a cool $70 without tax or shipping. I'm going to search now, but you know a good qualIty high pressure cap?

I personally like the OEM jap import ones with the Caution Hot! written in Japanese on them, cos they look cool, but i'd imagine your local auto parts store would have the full range of whatever the main domestic aftermarket brand is over there.

when I bought mine they didnt offer it either, now they do

Hate that long neck it looks so out of place once the factory shroud is gone
Debating modifying mine or just buying the new one and selling the one I have.

Mine doesn't have the long neck, just a filler with overflow nipple

So you want to fill it from the thermostat housing?

Yup, highest point.

For bleeding or aesthetics? The special funnel works great, simple and easy

When youve got two options for filling points, why wouldnt you use the highest point?

Im just interested in this thread as i was running an s5 rad and s4 pump housing in my FB so also had the two fill points. The overflow on the rad was blanked. Never had a problem with it.

New setup am running the koyo N-flow for s5 and s4 pump housing again. Will probably just blank the overflow at the rad again.

every FC is the same there arent tons of guys with air in their coolant

Im all for making things better it just seems like unnecessary work to take a perfectly good radiator and weld over it but people can do as they please with their cars

It would be a little much work too weld it, So I'm going to just run one cap higher pressure.
Like i wrote on my install thread, i probably should have just done a custom setup. The mounting is super easy on these cars. But I'm only saying that because i have access to a welder and have experience with minor fabrication.
Koyo is still nice to install just drilling my s4 brackets and chopping my stock shroud.
It just looks silly to have 2 filler necks,that i plan on going to a car show

i misunderstood you said you didnt care for polished now its a show car

I just like the look of clean raw aluminum over the shiny polished look. Cleaning polished is nice though

How did you go with this?
Im in the same predicament, s4 thermohousing and s5 koyo n-flow, and wondering again what to do with the two pressure caps and the two overflows.
previous setup was a standard s5 rad with a filler cap but no overflow and the s4 housing with cap and over flow.
I rigged up some temporary clear hose to both overflows so i can see whats going on, but im not too sure about it - should the overflow hoses be completely full of coolant, or are the air pockets normal? My thinking is that the engine pretty much bleeds the air out itself, but then if the air is still in the hose, it will suck it back in too?
apart from that, overflow bottle level rises when warm and lowers when cold as normal, and zero heat problems so far.

That 15-17Y0-N323 Cart Price Check Part:15-17Y0-N323 part number Misterstyx69 posted is all you need. It's $36. It replaces the cap/overflow nipple assembly you have on the top of your filler neck with one without the overflow nipple and a flat cap. No need to replace the whole neck.

Same thing for you. Then you have one overflow and one hose coming from the rad. You will still have two filler caps but only the one on the radiator releases pressure.