This is what my coolant looks like after 2 years – still a bright green
There has been quite a bit of confusion regarding the coolant to be used in the 124 Spider, much of it caused by Fiat calling out the Mopar purple Antifreeze / Coolant (# 68163848AB) that it specifies for other FCA vehicles using the 1.4 liter turbo engine, like the Fiat 500, Jeep Renegade and Dart Sport. There is nothing wrong with using that coolant, but it doesn’t mix well (at least color-wise), with the green FL22 premix coolant that Mazda uses to fill all vehicles built at their Hiroshima Assembly Plant, including the MX-5 and our Spiders. As you introduce more of it in with the green, the color will darken, eventually turning black. If you develop a coolant system leak, it won’t be as easy to differentiate from other fluids.
The photo above is indicative of how the coolant reservoir appears leaving the factory, so if you purchase a new vehicle with it appearing like the photo below, someone has probably added conflicting purple Mopar coolant.
Looks like dealer added Mopar purple coolant. Photo courtesy of Steve Russell. (click on it to enlarge)
Mazda also installs their metal coolant reservoir pressure cap, which specifies using FL22 coolant. As a note of caution, that cap is for the closed-loop pressurized cooling system (small section of the reservoir on the right, along with a port leading to that pressure cap) and should normally not be opened, especially if the engine is hot.
Coolant level should normally be supplemented via the integral (unpressurized) expansion overflow tank (the black plastic cap) to keep the level somewhere between LOW and FULL. In order for the system to not build up too much pressure, the relief valve allows some coolant to be released into the expansion tank when the coolant is HOT, but it will also eventually allow coolant to be sucked back in, as the system cools down again. This keeps the pressurized closed-loop system always full, but if you allow the overflow tank to go below LOW, or empty itself, not only might the pressurized system no longer be full, but in the cool-down mode, it will be susceptible to also pulling in air, which is not desirable in either the radiator or the heater core, as they become less effective, but in particular, air pockets — or hot spots — within the engine, can be dangerous, as they can overheat, crack or warp any part of the engine where air is trapped!
A hot spot is nothing more than trapped pockets of air or bubbles inside cooling system passages that prevent coolant from carrying heat away from those areas, causing that section of the engine to overheat and corrosion to start setting in.
Note that the overflow reservoir also has it’s own overflow hose, which releases excess overflow onto your engine belly pan. You will normally not see this overflow coolant on the ground, unless the pan is unable to contain the released coolant.
Steve’s expansion overflow tank
Anyways, getting back to the confusion over which coolant to use, Fiat has recognized and addressed the issue this year, as noted in their Mopar catalog for the dealers, and is now finally recommending Mopar # 68334695AA Antifreeze / Coolant (or equivalent), since it too is FL22 coolant, and matches the coolant Mazda installs (including the green color). It appears to be unusually expensive though, so if you might like to have some on hand in your garage, you might find it financially advantageous to procure this coolant at a Mazda dealer (around $20 for a gallon, if you ask nicely), rather than at your Mopar dealer.
Water should never be added to the reservoir, if a Premix configuration of coolant is being used, as it has already been added to that coolant. On the other hand, if a concentrate is being poured in, allow room for adding in distilled water in a 55/45 ratio (55% concentrate and 45% water). Just as in the case of topping off your lead-acid battery, the use of distilled water is very critical, not only for a proper pH balance, but to avoid introducing other minerals normally found in water (hard well water particularly) that will alter the chemical configuration.
photo courtesy of yorksboy; just about ready for some more coolant
Per the description of Mopar’s 68334695AA Antifreeze / Coolant, it is “5-Year POAT (Phosphate Organic Additive Technology)”, and therefore doesn’t appear to be Extended Life (which is 10-year / 150,000 miles), so keep that in mind if the coolant has been drained from your vehicle’s cooling system, and isn’t going to be re-introduced (as in a coolant flush), as the originally specified purple, Extended Life Mopar # 68163848AB Antifreeze / Coolant (or equivalent) now becomes a viable alternative to the FL22 formula, along with subsequent top-offs. If choosing alternative brands, it is most important that your coolant choice be OAT, extended life, ethylene glycol based with phosphate rust inhibitors (not silicates) and no 2-ethylhexanoic acid inhibitor (2-EHA free).
(another great article on coolants confusion)