Radiator Refurbishment

[Kaz-kzukNA1]

Placing the highest priority on another subject until the end of February so slow to respond.
Please bear with me.

If you really want, you can get the Mazda NF01-15-203 but as stated above, no need.

You can re-use the Koyo rubber gasket at least once.

The comment from 10 years ago about the spare gasket was based on the initial experience that was even before that.






Didn't like how the gasket sat at the mating surface of the radiator drain port because of the drain plug design.

Since then, don't know whether Koyo changed the material, the thickness, etc or may be it was one off unlucky at that time but for all the ones afterwards,
no problem even with the same plug design.






The Mazda parts consists of not just the flat rubber gasket but also the plastic drain plug.

Quite cheap in Japan and even several good quality aftermarket ones available.

However, probably around £10 in UK just for a single drain plug.

Although the Mazda plug looked to be the same diameter/pitch as the Koyo one, it's much shorter.

Also, the plug body is plastic whereas the Koyo one is machined aluminium.


I own MX-5 and change coolant every 2 years.
In old days, used to create own coolant mixture at 30% and change it at short interval.
I still prefer 30% from the cooling performance point of view.

If you own MX-5 or other JDM (Mazda/Toyota/Nissan/etc) using the same plug,
you’ll know the #3 slot on the plastic drain plug could get damaged.

So make sense to replace the plug and the gasket as a set every time.


As mentioned above, Koyo drain plug is machined metal.

If changing the coolant frequently, just replace the gasket when required.

Look for the M10 flat rubber seal.

From what you wrote so far, you either have the Koyo Rad ready to be installed or about to get one.
You can measure the one pre-installed on yours but this is what I have.

Should be the same unless Koyo changed the design spec recently.

ID: 10mm, OD: 16-17mm, THK: 2mm




The flat gasket of the Mazda one is thicker (2.5-3mm) than the Koyo one.

My preference is THK 3mm.


Don’t know what material in use for the cheap ones on the market but you can find the EPDM one as well.

If not sure, just replace it every time when you drain the coolant.

Plenty of M10 flat rubber gasket on the market with all sorts of different spec.


It's in contact with the coolant chemical passing through the threaded section of the drain port, thermal shock, all sorts of debris, etc so you can get some idea on the environment.


Again, you can re-use the Koyo rubber gasket at least for the next service.


Don't know if it will fit and not sure of the material but the rubber seal at the TB tensioner adjuster bolt could be similar size.


Kaz

[Formula 91]

Thanks Kaz for clarifying the seal required at the drain plug.