coolant maintenance of nissan leaf
the original coolant that comes in the leaf from nissan is a silicate free 50% water to 50% ethylene glycol based premixed solution. according to the technical manual of the 2013 leaf, it is recommended to replace the original coolant after 15 years or 200,000kms; whichever comes first. however, it is a good idea to check the state of the coolant once every year or so because the effectiveness of the coolant may be reduced due to various reasons.
the cooling system in the leaf is quite similar in principle to an internal combustion engine's cooling system. the main difference is that the leaf’s cooling system lacks a traditional thermostat and operates in a lower temperature range than an i.c.e. vehicle. instead of cooling an engine block, it cools the integrated unit which houses the on-board charger, dc-dc converter, motor's inverter, and motor. the coolant runs through the housing of those parts to collect heat and comes back to a fanned radiator to dissipate the collected heat out to the environment, and the cycle continues due to the water pump being activated/controlled by the car's computer.
due to the similarity in function, the maintenance needed to keep the leaf’s cooling system in check is no different than to a regular vehicle.
maintaining the proper water-to-antifreeze ratio
pure water is the best heat transfer agent. water has a higher “specific heat capacity” than of pure antifreeze. but water freezes at 0° celsius and boils at 100° celsius. also water causes corrosion inside the cooling system. to overcome the said shortcomings of water, antifreeze is added to water in order to lower the freezing-point, increase boiling-point, prevent corrosion and also to provide lubrication. the downside to adding antifreeze to water is, the “specific heat capacity” of the coolant mixture gets lowered and the viscosity of the liquid is also increased compared to pure water. the higher the amount of antifreeze in the mix, the harder the water pump has to work to collect and expel the heat generated by the car. therefore, wasting energy and reducing the overall efficiency of the system. even in the coldest of climates, the maximum amount of antifreeze in the mix should not exceed 70% according to most antifreeze manufacturers and experts. for an all-year round hot climate like ours where freezing is not applicable, we can safely go as low as 25% antifreeze and 75% water. this is evident from the fact that wurth brand blue coolant marketed in sri lanka is supposed to be diluted in the ratio of 1-part antifreeze to 3-parts water according to instructions on the bottle as well as wurth management from their branch in nugegoda (near urban wetland park).
the boiling point for a mix of 30% antifreeze and 70% water would be around 105° celsius according to the sources listed below. it should never get that hot in a leaf unless there is some kind of fault in the system such as failure of the radiator fans, water pump malfunction, etc. in which case the car's computer will shut down the car if detected.
however, if you’d like your coolant mixture to be as close to the original factory ratio, it is recommended that you stick to the nissan recommended "all-weather" ratio of 50% antifreeze and 50% water which would provide boiling protection of up to about 107° celsius.
checking the status of your coolant
when checking the status of your current coolant mix, the difficulty is in accurately determining the current ratio of antifreeze-to-water; even though several methods exist to measure the composition of a mixture. most tend to give varying results depending on variables like ambient temperature, quality of devices, accuracy of charts/ formulae, etc.
the most foolproof way imaginable is to first get a sample of brand new 50/50 nissan blue coolant and get a target level using either a refractometer or a hydrometer. by using that level as our goal, we can test our current coolant mixture using the same device and check whether we need to add more antifreeze or water to bring our mixture to the intended level. however, please be noted that instruments such as refractometers and hydrometers only indicate the "specific gravity" of the mix. it cannot tell us the exact ratio of antifreeze:water of the mixture, nor can it tell us whether the antifreeze/anti-corrosive chemicals in the mix have degraded or not.
most hydrometers and refractometers will show between -35° to -30° celsius as the freezing point reading for coolant mixed at the 50/50 ratio. if your current freezing point reading falls within that range, we can assume that your coolant mixture is still close to the original. but as previously mentioned, the freezing-point reading (which is an approximation from specific gravity) is not a good measurement of the effectiveness of your coolant.
if your original nissan coolant is near it’s end of life (200k or 15yrs) or if you're unsure what the previous owner of the car has done to the coolant; you should just skip checking the state of your coolant and completely flush out the system and replace with brand new nissan blue coolant or any other good brand silicate free coolant mixed to the desired ratio.
coolant flushing procedure
in the leaf, when the radiator and reservoir tank is drained, it takes about 3 liters of new fluid to fill it back up to full level. but the total capacity of the leaf cooling system is 5.3 liters according to the manual. what that means is about 2 liters of old coolant mix was still inside the system. so keep in mind that if you simply drain and refill the radiator/reservoir, it would not be a 100% true flush of the system.
due to the above mentioned complication, if someone wants a true coolant flush, the recommended procedure is to:
- shut down the car
- drain coolant by removing the radiator drain plug
- close drain plug and fill with de-ionized distilled water
- turn the car on (with a/c running) and let the water pump cycle the water for a minute or two
- stop the car and drain again and repeat above steps until all colored coolant has left the system and only clean distilled water remains
- then drain about 2.5 liters of distilled water and add 2.5 liters of 100% concentrate nissan blue or equivalent silicate free antifreeze
- turn car back on and let it cycle for a few more minutes to bleed out air and add distilled water if the level drops
doing the above procedure will guarantee a ratio close to 50/50 which you can verify by doing the math ( 2.5 / 5.3 x 100 = 47% ). if you’d like to go for the wurth recommend 25/75 ratio, simply use 1.5 liters of concentrate antifreeze.
I have personally done a true flush as mentioned above and done a 25/75 ratio with wurth blue concentrate for my 2013 leaf. if your car is a different year than mine, please refer to the correct year manual and find the full capacity of your cooling system and then re-do the math.
note 1: only use deionized distilled water when mixing with coolant. never use tap water.
note 2: it would be unwise to mix different brands if/when topping up antifreeze (i.e. when not doing a true flush). if unable to find nissan blue or unsure what brand coolant is already in your system, it would be better to do a true flush and replace with brand new antifreeze as per the above procedure.
additional resources:
- a video that demonstrates checking the ph balance of coolant using test strips and checking freeze-point using a refractometer: https://www.youtube.com/watch?v=5OC9nM0Frb4
- a video that shows how to use a hydrometer to check the freeze-point of coolant and use a voltmeter to check electrical conductance: https://www.youtube.com/watch?v=xVHRpBn-yaA
- freezing-point, boiling-point, specific heat, etc. charts for coolant mixtures: http://www.engineeringtoolbox.com/ethyl ... d_146.html
disclaimer:
none of the information presented here is my own opinion and can be verified by anyone by searching the internet and/or talking to industry experts.
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