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Heads Up for NC Owners

A little note from Larry Garner for those of you whose Miatas are from 2006-2009:

We recently got some coverage for Ritas’ mom and got away for a few days and visited friends in Helen, GA, and drove some of the great roads in the area. We get back and after the NC sat for a few days, noticed a small puddle of fluid underneath.

An exam finds that the top of the radiator reserve, where the cap sits has cracked and separated under pressure. On further info search, I read that this part has a life of about 10-years; our car was built in 11/07. Glad it didn’t happen on that trip.

Kinda like when we drove the NA to Niagara Falls in 2012 (2400 miles) and two weeks after we get home, I find a hair line crack in the original radiator.

One thing I’m finding is that parts for the NA are very plentiful and inexpensive but not so much on the NC. There is an upgrade for the NC, in aluminum, but it’s $250, while the OEM one is around $70 or so on-line. I have one on order and it’s an easy swap.

— Larry

5 comments to Heads Up for NC Owners

  • Daryl Shipman

    I purchased the aluminum tank for my 2013 NC from JEGS for $210 and installed it myself. See attached photo.

  • Tom Varallo

    I learned of this issue from the folks at Zoomin in 2016. It’s an issue because on the NCs, the overflow tank is actually part of the pressurized cooling system, unlike most other cars where the tank is open to the atmosphere. If the plastic tank fails catastrophically while the engine is operating at speed, you may not have enough time to shutdown before you loose enough coolant to cause engine damage. Like Daryl, I replaced mine with a welded aluminum version by Mosimo through Moss Motors for about $250. Haven’t worried about it since.

  • David Brock

    You scared me enough to convince me to go ahead and buy one. $228 and change from Amazon. No tax and 5% back for prime for a grand total of $216 and change. Any special procedures needed to avoid air pockets or is it engineered well enough so air will quickly work its way to the overflow?

  • Daryl Shipman

    I siphoned all of the coolant from my old tank and then was careful when I disconnected the hoses not to let them drain. Then I installed the new tank using new worm drive hose clamps and refilled the new tank using the coolant I had siphoned from the old tank. I ran the engine with the radiator cap off till the coolant was warm, squeezed the hoses to expel any air, then started the heater and squeezed the hoses again. Finally I topped the new tank off with clean water and installed the cap. Since I only had to add a very small amount of clean water I didn’t think it would affect the coolant mixture. I did not have a problem with air pockets.

  • Jennie Hodges

    Good info for NC owners.