Friday, January 3, 2014

Comparing thermostats - Mazda OEM vs NAPA

I took a bunch of pics and measurements of various thermostats when I was testing them on my Miata.  I thought I would share them in case you are curious.  I compared and measured them looking for differences to substantiate why the OEM might be 'better' as some people say but could not notice any difference in materials using my naked eye or primitive measuring tools.  Even the spring feel similar when compressed using my hands for force.   Not very scientific but good enough to establish that the NAPA stuff is not made of weak springs or materials that are flimsy.

First, let me start by saying that I only compared the OEM Mazda thermostat with the NAPA sourced thermostats.  The Miata uses a generic, common sized thermostat with a 52mm / 2 1/16" diameter.  NAPA was the only parts store that would give me a hard time when I ask for a generic 2 1/16" thermostat in 180* or 160*.  Every other part store would only look up the Miata and sell me whatever the stupid system said was the one.  Just walk into NAPA and ask for a generic thermostat in 2 1/16" and 180* temp with the part/reference number of 142 and they should be willing to help you.

Here is a pic comparing the OEM thermostat with the 180* #142 Napa thermostat.  The NAPA is shorter but it makes no difference as it fits the thermostat housing / water outlet housing perfectly.

Here is a pic of the inside of the thermostat housing (aka water outlet housing as the part's store books refer to it...).  The thermostat can be shorter and still fit.  However, it cannot be longer / taller the the OE and fit.

Here is a pic [attempting to] measuring the size of the hole that the water circulates through when the thermostat opens in NAPA vs OE.  I couldn't find my calipers so I used a tape measure - sorry.  The diameter of the hole is very similar.  Perhaps only a mm larger in the NAPA.  Napa on the left.  OE on the right.

OEM thermostat:

Hope that was interesting in some way.

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