124 Spider ~ Coolant Confusion

[This information was originally a sidebar to the Coolants section of my Specs page, but since it was getting rather lengthy, it has become it’s own article, with photos instead]

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.  

black 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.

There really is no need to feel compelled to top-off the expansion tank.  Just insure that the level (when the system is cool) is at or above the LOW level.  If you are adding  coolant, it should normally be supplemented via the integral (unpressurized) expansion overflow tank (the black plastic cap), 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. 

[added 5/16/2020]
I never gave much thought to this overflow hose, but since it also serves as a vent for transfer activity between the pressurized system chamber and the overflow reservoir, unlike in vehicles without bottom pans, perhaps we shouldn’t panic and assume the water pump is failing if we occasionally get a whiff of antifreeze, as this vented air is perhaps more likely to be drawn into our cabin air inflow.  Similarly, don’t assume the worst just because you see a green stain on the belly pan – it could just be vented overflow coolant. 

Prior to a large repair job, shine a black light at a suspect water pump, as it will confirm an actual leak.

black coolant1

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.

Coolant Mopar

Mazda Coolant

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 de-mineralized (deionized water is best, although not easily obtainable;  distilled is your next best choice) 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.

coolant low

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 (reflect that changeover on the coolant reservoir bottle cap label).

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).

Coolant Change Interval:  10 years or 150,000 miles (240,000 km), whichever comes first; source, however I disagree, since per the description of Mopar’s 68334695AA Antifreeze / Coolant (FL22), it is “5-Year POAT (Phosphate Organic Additive Technology)”, and therefore isn’t an “Extended Life” coolant – so 5 years or 75,000 miles (120,000 km).

(another great article on coolants confusion)

15 thoughts on “124 Spider ~ Coolant Confusion

  1. Just to be a bit more precise:
    The reservoir below the pressure cap is normally always filled completely, so no chance to top off your coolant via this port at all.
    Really the only option is via the black plastic cap.

    As for non OEM coolants: German company Ravenol lists some FL22 compliant products. Description claims that they’re also green.


    These products are also available @ Amazon.

    Liked by 1 person

    • I have a doubt, FCA is authorized to use the FL 22 refrigerant but was it considered that our monobloc is in cast iron? (Mx5-ND completely in aluminum) FL 22 do we know the FL 22 specifications? Thank you


  2. I think you meant coolant 😉 and of course FCA authorized Mazda to install FL 22 into our cooling system.

    I’ve had a nice technical article link at the bottom of my article, which indicates to me (if I’ve interpreted it properly) that all of the special coolant enhancements are aimed at gaskets and the aluminum components (just about anything, including plain water, works for iron).

    Japanese conventional coolants contain no silicates, but they do contain phosphates for fast-acting protection, plus other inhibitors. Extensive Japanese tests have shown phosphates to be a good corrosion inhibitor for aluminum, and particularly effective in protecting water pumps from corrosion after cavitation erosion/corrosion.


    • I apologize for the bad English, I read all the articles and links contained in the page (the page is fantastic and it is a great contribution for us 124ists) and just reading the link “Honda and Toyota use a new extended-life OAT coolant-made with sebacate as the only organic acid-no 2-EHA. Sebacate isn’t quite as effective in combating corrosion at lower pH levels, but because that’s more of a cast-iron issue, it apparently didn’t concern the Japanese. Both Honda and Toyota do continue to avoid silicates, but add a dose of phosphates to provide fast-acting aluminum protection, particularly to recoat the water pump after cavitation erosion/corrosion.” I came up with the doubt that the Japanese specifications are not suitable for cast iron monoblocks, or am I wrong?


  3. I found another interesting article that states:

    Phosphate is an anodic inorganic corrosion inhibitor that works well to protect aluminum and cast iron components from corrosion. Phosphate acts as a pH buffer and is often used by Japanese car makers. However, phosphates react poorly with hard water and can form scale in the cooling system which can plug up the radiator and heater core [not a concern with premix].

    I am not an expert, so my opinions are based on what I’ve read…


    • Very interesting! although I think FCA has adopted a convenient solution, perhaps not the best one. I study the attic well to know what is the best solution for our engine, I also asked Ravenol and Noraison for information on the correct specification to use. Your information is very useful. Thank you


  4. After seeing some commentary regarding failed water pumps, I’ve added a paragraph to my article as I’ve convinced myself that the occasional whiff of antifreeze after a drive is perhaps not reason enough to assume my water pump needs to be replaced.

    I never gave much thought to this overflow hose, but since it also serves as a vent for transfer activity between the pressurized system chamber and the overflow reservoir, unlike in vehicles without bottom pans, perhaps we shouldn’t panic and assume the water pump is failing if we occasionally get a whiff of antifreeze, as this vented air is perhaps more likely to be drawn into our cabin air inflow.

    Replacing a water pump (new timing belt too) won’t be cheap at an independent shop:
    ◉ there are a few special FCA tools required (1.4 L timing belt positioner, scanner, etc)
    ◉ Mopar charges $1800 / year for access to FCA vehicle service manuals
    ◉ Mopar charges a lot for parts
    ◉ the hourly rate is probably close to $150, and I bet it takes about 3 hours (it’s not an easy job)

    so independent shops can’t offer economy, but if the mechanic is conscientious, at least you’ll get the job done properly.


  5. Hi, thanks for the very helpful article on the 124 coolant issue. I’ve had my spider for a year and would be interested to see how often anyone who reads this has to top up their expansion tank. Whilst under warranty I had a Fiat garage here in the UK pressure test the coolant system in case there was a leak and they could not find any problem, despite the level dropping fairly regularly. There are no obvious signs of gasket damage and no drips from the car (also nothing seemingly on any bottom pan). Is this a quirk of the Spider? Keep up the good work!


    • Thank you Richard. I’ve reworded the associated paragraph to hopefully clarify that there really is no need to top-off the expansion tank.

      There really is no need to feel compelled to top-off the expansion tank.  Just insure that the level (when the system is cool) is at or above the LOW level.  If you are adding  coolant, it should normally be supplemented via the integral (unpressurized) expansion overflow tank (the black plastic cap), somewhere between LOW and FULL. 

      In answer to your question, I’ve only added coolant once, since I wasn’t yet aware that there really was no need to feel compelled to top-off the expansion tank just because it was near LOW. 😉


    • Hi Richard,
      over the course of one year ( ~ 6000km driven ) my Spider’s coolant level would slowly drop from high to low. Dealer then always topped it off during the anual service.

      Also not seeing any signs of leakage and I’m not smelling coolant out of the exhaust. So I suspect that some water slowly evaporates through the overflow hose on the refill cap.


      • Hi Tobias, thanks very much for your comments – very helpful. I reckon my Spider probably does the same over a similar number of miles. Worth keeping an eye on! Best wishes.


  6. Hello Dan,
    I’m getting desesperate, i want to drain my coolant in order to install silicone hoses on the coolant system.
    The only tutorial i found on the forum says drain the coolant by the petcock …. fill it back.
    There’s no mention of the pressurized cap and the overflow part just beside.
    Is there any coolant system diagrams or step by step tutorial somewhere ??
    I looked up in the 2016 mx5-nd that you gave the link but this is not our coolant system.
    Could you help me please.
    I’m French from Québec (Canada) so excuse my poor English.
    That’s why I’m not going on the 124 spider forum to ask questions.
    Thanks for reading me and Have a great Christmas Time.


    • You need to vent the (not-hot) coolant, in order for it to drain, by removing the pressurized cap. If you are putting the same type coolant back afterwards, don’t worry about the overflow tank.

      Per the service manual: Remove the belly pan, then remove the RH wheelhouse splash shields, then open the radiator drain valve.


  7. I thank you so much Dan,
    So if i do understand well, instead of having the cap directly on the radiator, the pressurized section of the plastic reservoir is à sort of extension of the radiator.
    Well, anyway, you made my day !
    I love your work and I always read your articles with great attention.
    Have a great Christmas Time Dan.
    Thank you again
    Jean-Guy (the FrenchGuy) 🤣

    Liked by 1 person

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