What is the point of changing coolant if it get's constantly replaced?
 

Based on the maintenance schedule of the coolant:

1st replacement interval is 11 years/137,500 miles (220,000 km).
2nd replacement interval is 6 years/ 75,000 miles (120,000 km) after the 1st.

...I don't really understand the point of replacing the coolant. Why would it need to get replaced if you're constantly replenishing it? Especially during a long period of 11 straight years, wouldn't it have been replaced several times over?

Edit 1: When did I ever say it was being replaced constantly? I said "constantly replenishing". Constant could be any frequency. The definition of constant means occurring continuously over a period of time. So let me be specific, "topping off when needed". Also my car is still relatively brand new, under 10k miles. There aren't any signs of leaks that I know of, so it's doubtful I have a leak.

What? How is it being replaced constantly? Unless you have a serious leak it would never happen.

Me thinks there is a piece of the puzzle missing.

Replacing (the entire coolant) vs topping off is NOT the same thing.

It's like saying "my car burns a quart of oil every month, every 6 months I have an oil change so I don't need to change my oil"

Wow kids theses days. Would not be surprised if he clams he's an engineer of some kind.

Any who, short answer, the coolant brakes down over time and it's not as effective.

Your Google-fu is weak young grasshopper

I'm new to the FRS, just got mine a month ago, but reading around here I've seen several people talk about these cars eating coolant. I can't say if mine does as I just got it. But I think the OP was sort of referring to that issue. If you're eating through and topping off the coolant at a higher rate than the scheduled interval then theoretically you've changed it a few times. Just speculating on what the OP was getting at. I'm not sure how widespread the coolant eating problem is or at what rate they are eating it.

But lets say it burns 1 quart a week. In 6 months you have put 24q in it. I used to have an Integra GSR that was hydrolocked and sat up for a holiday weekend waiting for an insurance adjuster to look at it. By the time he arrived it was dried out and would start. They screwed me over and didn't cover it. The damage on the cylinder walls was was so bad from those 3 days that even after boring to the service limit you could still see the damage. After a few years like that it would eat up the rings and burn at LEAST 1q per week.

I think the OP was kind of poking fun out of frustration that his car is using coolant.

This is news to me, If my car was eating coolant I would be a tad concerned. The engine cooling system is pretty much a closed loop. Topping it off every few months with a few ounces of coolant would not cause all of the coolant to be replaced, even after five years.

I'm willing to be corrected on this one but if my twin was eating coolant to that extend I would be checking for leaks and doing a coolant system pressure check. (Or getting the dealer to check it under the warranty).

See Edit #1.

But how often and how much are you having to add? It should go away if you aren't burning it or leaking it.

I have owned the car for 3 yrs now and I have only topped the coolant once myself (roughly .2liter) and once guys at Subaru dealership did during the oil change. BRZ has 7.2L of coolant (for manual car). I hardly doubt you will be "replenishing constantly" to add 7.2L of coolant in 11years. If you do have to add that much coolant, then you have bigger problems.


:bonk:

As pointed out, see the title of your own thread "What is the point of changing coolant if it get's constantly replaced?"

The point of replacing coolant is so that you replace the capability of it to 1) protect the cooling surfaces it contacts, and 2) continue to act as antifreeze. Additionally, since there is no filtration capability, replacing the coolant in its entirety means you can remove any contaminants that are suspended in it.

"Topping off when needed" is great if it was pure water and nothing else, except if you ran only water the insides of your engine block would soon lose the ability to transfer heat to the water. Aluminum blocks oxidize over time as well as iron blocks, and once this takes place you will find it increasingly difficult to run the engine cool, especially if you take it to the track or otherwise live in very hot/humid conditions.

The entire point of having to replace coolant is so it continually provides the ability to cool your engine over time. The reason why the interval becomes more frequent over time is because the manual is written assuming some corrosion with the stock block will happen, thus you need to increase the frequency you replace the fluids as mileage or time increases.

-alex

For sure don’t run pure water. Your water pump will be gone in no time at all. I live in Florida so the antifreeze aspect is rarely a concern. It’s the anticorrosion properties that are critical here.

Yup, it's why the manual is written the way it is, for people that don't understand how cars work.

Admit it, it is something we've wondered at one time or another, right? In my teens I had a friend who owned a Rambler. It burned about a quart of oil every 500 to 1000 miles. He decided there was no point in changing it since it was effectively changing itself every 5000 miles. In fact, we thought the car was better off because it always had 2 quarts in it that were less than 2000 miles old.

It ran like that for several years until some f&^kwit stole the thing and ruined our experiment. If memory serves, one of the Car Talk guys, Tommy, I think, did the same thing to a Dodge Dart. I don't recall how the car died, but it ran for a long time.

The key is that the consumption/replenish rate be high enough that the chemistry of the fluid is constantly being renewed. :D

I solved my own question and posted it on stack exchange mainly because I couldn't get any real answers here. If you're interested, it's at this link ---> https://mechanics.stackexchange.com/...antly-replaced
@ermax, I think you meant "shouldn't", and I don't know, I just checked and my coolant reservoir is at the low mark. I will more than likely add some in and frequently check for any changes. My question is unspecific to any issue.
@mav1178 I'm not sure what you mean by this ---> "Topping off when needed" is great if it was pure water and nothing else..."
@Capt Spaulding I encourage you to read my post on stackexchange. You may have a different perspective on the issue.

Cool story except you didn't answer your own question.

Really? That's your own answer to your own question?

I think we need to start another thread to discuss this same topic.

My response was meant as a joke. I.E. a car that is in such bad shape that it's hemorrhaging coolant and oil so fast that you are, indeed, constantly replacing it, has problems far beyond what a fluid change can address.

To the extent that your initial question, "What is the point of changing coolant if it's getting constantly replaced?" could be answered it was addressed early in the discussion. 1) It's NOT getting constantly replaced, so 2) Its anti-corrosion properties degrade with time and "use" 3) and the degraded chemical compounds (combined with other foreign matter) precipitate out of the solution and need to be removed from the system and replaced by fresh fluid.

In essence, you could not answer your own question because it contains a faulty assumption - that the coolant is "constantly being replaced."

@mav1178 - Um, but I did. @Capt Spaulding - It doesn't get constantly replaced, we already know that. You don't need to keep beating the semantics of the thread title. I already mentioned replenished in the description.

If the entire cooling system was closed, then "topping off" would never be a phenomenon, but it is because the coolant reservoir vents to outside air, but nobody here has mentioned that, so it IS getting replenished here and there, but rarely necessary. My question was about the dynamics of fluid exchange primarily, no sure why no one could understand that here except for the community on stackexchange.

Well, I don't know about the other FR-Ss but my 2013, with 20 some thousand miles over the past 4 years, hasn't "used" any coolant ....... :popcorn:


humfrz

Well, ghostzfh, I reckon you are either just yanking our chain or you're waaaay overthinking this situation ........ :iono:

Since you're at 10,000 miles, you have several years/miles before the coolant replacement is scheduled.

I suggest you relax and enjoy driving your machine ....... :thumbsup:


humfrz

I understood your question perfectly.

If you think stackexchange can answer all your questions, why start 3 threads on the same topic?

It's very simple, the mechanism that regulates the cooling system is the thermostat and radiator cap.

The thermostat ensures operating temperature is above a minimum so optimum heat is retained for combustion. There's always an ideal operating temperature given differences in thermal properties of different metallic and non-metallic components of an engine.

The radiator cap basically regulates overheating, in a nutshell. Additives may raise the boiling point of the coolant but the amount of heat that the cooling system can carry away is limited by several factors like ambient temperature, surface area (of radiating surface, i.e. radiator), etc. The radiator cap is designed to hold up to a certain amount of pressure (stock caps usually are 1.1kg/cm2 or around 1.078bar), then the spring releases pressure into the overflow tank ("boils over") and this release in pressure will help reduce the heat in the system. When the engine is cooled down, there will be a vacuum in the cooling system, and it pulls coolant back in from the overflow tank.

The overflow tank needs to be refilled when it is excessively low, yes, but I get the feeling your original question was only with regards to topping off the overflow tank. Topping off this vs replacing your coolant at 100k+ miles is not the same thing.

What is the point of all this? Coolant is water + additives. Additives break down over time, the ability of the additives to prevent corrosion inside the cooling system is reduced and thus your ability to cool the engine is compromised with usage/time.

What you CANNOT do is view this fluid exchange as the coolant being "replenished" or "replaced". Nothing about this is changing anything about the coolant in the block, other than replacing what may have boiled over when the car was hot and the radiator cap was venting excess pressure. You should view it as "putting back what was taken out", which means the bulk of the coolant inside the engine is the same.

Or you can spend 30 seconds and Google all this information.

My money is on option #2. You're cooling a lump of metal with an antifreeze mixture and a pump, not building a goddamned time machine. If you drive more than 10 minutes at a time (long enough for the thermostat to open), all the coolant in the system is homogenous...you don't need to worry about what's in the block being different from that in the radiator or the overflow tank. Crrrripes....


Edit...didn't see the reply above, which was a much more thoughtful way to say "stop making something out of nothing"

You know, I've reread the original post and the stackexchange exchange and I'm still not completely sure what the question is. Is it about the thermodynamics of the cooling system and how/why the overflow bottle works as it does? It is still about the "replenishing" of the coolant?

The latter question (which still seems to be at the core of the discussion on stackexchange) is as @humfrz implies (and the folks on SE confirmed) a non issue as there is no meaningful replenishing happening.

edit: If it's just where does the coolant go as the level drops by tiny increments over the years and miles, @steve99 answered that as clearly as can be in another thread.

I know for me, my coolant kept 'disappearing' pretty fast ...
I met a guy that grabbed some electrical tape (I think that's what he used) and wrapped it around the black rubber hose that sticks out of the coolant overflow tank (where you fill it up). After this little bit of 'air-tight' sealing, my coolant has nearly no loss in coolant (just a splash now and then).