car is 2017 nissan sentra  manual states 7 yrs or 100,000 miles change coolant this car has ONLY 14,000 miles i can't beleive  coolant could break down  with so few driven milescould some of the experts here have an answer?

5 minutes ago, sjay said:

car is 2017 nissan sentra  manual states 7 yrs or 100,000 miles change coolant this car has ONLY 14,000 miles i can't beleive  coolant could break down  with so few driven milescould some of the experts here have an answer?

It’s 2024. So it’s been 7 years; chemicals do degrade over time.

Antifreeze degrades faster in the bottle than in your car's cooling jacket.  They add silicates, which tend to polymerize to a gel in a couple years if the solution is just sitting on a shelf.  In a car, the heat/cool cycles and circulation actually prevent that silicate instability.  However...

The glycol portion degrades in the presence of oxygen, which means if air gets into the cooling system it will break down faster.  This process forms acids like glycolic, formic, acetic and oxalic acids. These can corrode the radiator over time.  So changing the coolant is a good idea.

- former shade tree mechanic 

38 minutes ago, sjay said:

car is 2017 nissan sentra  manual states 7 yrs or 100,000 miles change coolant this car has ONLY 14,000 miles i can't beleive  coolant could break down  with so few driven milescould some of the experts here have an answer?

It's not "breaking down" exactly, but some components may be used up. Anti-freeze also contains things such as corrosion inhibitors which plate out on surfaces and eventually become used up. It's inevitable in cars that there will be different metals in contact with the coolant which can set up electrochemical corrosion over time. There can also be deposits from corrosion that accumulate in the cooling system and should be flushed out so that you don't get blockages in the radiator, for example. It's cheap and easy to flush out and replace the coolant so hardly a big deal to do.   

1 hour ago, exchemist said:

It's not "breaking down" exactly, but some components may be used up.

Ethylene glycol doesn't break down? 

https://en.wikipedia.org/wiki/Ethylene_glycol

"Ethylene glycol ... breaks down in air in about 10 days and in water or soil in a few weeks." 

51 minutes ago, swansont said:

Ethylene glycol doesn't break down? 

https://en.wikipedia.org/wiki/Ethylene_glycol

"Ethylene glycol ... breaks down in air in about 10 days and in water or soil in a few weeks." 

OK, it will oxidise in time in air. But there should not be significant amounts of air in the coolant system.