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Heineken's Garage

Coolant Tank - Replacement

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General information

The NSX's coolant tank is quite different from the coolant tanks used in Japanese high volume cars. In most of these vehicles the coolant system "breaths" into the coolant tank by pushing excessive coolant into the tank and sucking it back during cool-down. The cap of such a reservoir doesn't hold pressure and the tank is therefore not pressurized.

At the NSX the tank is part of the pressurized cooling system and therefore subject to much more thermal stress. Additionally, it's internal sections are constructed in such a way that air bubbles are removed before the coolant is drawn out of the tank, improving cooling efficiency during high engine stress.

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The Coolant Tank

Known Issues

The coolant tank in the engine bay is a consumable item, similar to the front radiator. Over time, the white material gets more and more opaque as the plastic hardens and becomes more brittle up to the point of failure. It should be possible to check the coolant level without using an additional light source. If that becomes necessary, it's advisable to think about a replacement.

Leaks become visible as green, crystallized residuals inside and below developing cracks. If these are observed, replace the coolant tank at the next occasion and avoid thermal stress situations. Typical failure points are around the seam, especially at the mounting tabs, and along the "MIN" / "MAX" marks, preferably at the bottom half.

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A crack near the mounting tab ..

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.. further developing downwards.

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Cracks at the "MIN" marker


Replacement

Replacing the tank with an OEM unit is advisable due to it's special internal design and possibility to check the fluid level from the outside. Third party alternatives made out of metal do have the advantage of not hardening but often don't provide above features.

Honda's part number is: 19101-PR7-A02.
Prices vary from country to country, it's advisable to check different sources.

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An OEM replacement tank

To replace the tank without loosing any liquid follow this approach.
A pair of pliers, a plug to close off the bottom hose and a clean, flat tray to temporarily store coolant fluid is required.


  1. Ensure the engine is cold to avoid getting scalded.
  2. Unbolt the tank from it's mounting points and disconnect the overflow tube.
  3. Remove the top hose (near the filler cap)
  4. Lift/move/rotate the tank to pour as much coolant as possible through the top hose flange into the tray.
  5. Rotate the tank in such a way that the bottom hose gets above the remaining coolant level.
  6. Remove the bottom hose and plug it (avoids a leak when snapping back to its original position) and remove the tank from the vehicle.
  7. Connect the new tank to the existing hoses and overflow tube. Pour the coolant from the old tank and the tray and into the new tank.
  8. Carefully install and tighten the mounting screws.
  9. Check the coolant level and top-up if needed.
  10. Transfer the filler cap from the old to the new tank.
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