Coolant level dropping & Dirty coolant

[Ultramaroon]

Originally Posted by Bonburner

To quote myself:

That's completely wrong. The reservoir is not supposed to be air tight. They never are.

[Bonburner]

Originally Posted by Ultramaroon

That's completely wrong. The reservoir is not supposed to be air tight. They never are.

It isn't air tight, the coolant yellow cap has a hole.
Doing what I said reduced the rapid amount of evaporation due to the loose fitment of the rubber hose.


Edit: I realized I said air tight in my first post. I was referring to the part where the rubber hose fits into the coolant. Not the entire coolant and overflow coolant system, that shouldn't be air tight.

[Ultramaroon]

Originally Posted by Bonburner

It isn't air tight, the coolant yellow cap has a hole.
Doing what I said reduced the rapid amount of evaporation due to the loose fitment of the rubber hose.


Edit: I realized I said air tight in my first post. I was referring to the part where the rubber hose fits into the coolant. Not the entire coolant and overflow coolant system, that shouldn't be air tight.

The advice from the fellow owner was well intended but misguided. The expansion reservoir is specifically designed to vent to atmosphere.


It wasn't until I became involved with this forum that I discovered how widespread this misunderstanding really is. I guess it's because, for most people, coolant loss is a frustrating mystery.

[Icecreamtruk]

While it may be normal or acceptable for most people, you may in fact have a head gasket that is on its way out. My car used to go thru coolant as well, very little initial, needing a top off between a few months. Then at the beginning of this year it got worse, while hot it was pushing so much coolant on the overflow that it kept going out of the plastic hose on the top and it eventually even splashed on my windshield on track.

I had the heads pulled appart, and yes, head gasket on the passenger side had a leak big enough to push some of the compression from the cylinder into the coolant, presuring the system beyond what it can handle. Not a pretty bill, but I track my car very regularly, so while you may never get to that point, its pretty clear that water misteriously dissapearing like in your case is probably a weakened head gastket that leaks a tiny small amount under certain circomstances only.

[new2subaru]

There's no possible way it's a closed system. It has to vent or the reservoir would implode when cooling.

I haven't touched my coolant since new (3 years-30,000km) and check it regularly.

[Bonburner]

Originally Posted by Ultramaroon

The advice from the fellow owner was well intended but misguided. The expansion reservoir is specifically designed to vent to atmosphere.


It wasn't until I became involved with this forum that I discovered how widespread this misunderstanding really is. I guess it's because, for most people, coolant loss is a frustrating mystery.

I fully understand the expansion of water (and whatever else is in the coolant that can vaporize) will increase pressure in the overflow tank. But there is a hole in the yellow coolant cap to allow for air pressure to release. I personally found that the coolant was evaporating way too fast. Meaning the coolant in the system is not 50:50, more like 45:50 now. If not worse, because I have been regularly topping it off with the 50:50 coolant from subaru. Up until I added an extra bit of sealing to the system.



I drive 450 miles in the summer California desert heat without any issues with this set up - multiple times. It has preserved my coolant from over evaporating without anything blowing up.




All in all, feel free to do as you feel. But I'd suggest you do a flush sooner than later if you don't replace the evaporated water with DI water occasionally.

[redwine]

Hey guys,

appreciate all the reply
From the reply, looks like my coolant loss is on the high side.

i tried to google about the minimum coolant ratio with adequate corrosion protection.
(Freezing not a issue since my location is all year summer)
Look like that ratio is btw 10% to 30% coolant.

Assuming the factory fill is 50%/50%, evaporation is 0.5L coolant + 0.5L water,
If i top-up 1litre (0.25L coolant + 0.75L water) every 4mth,
After 2years / 6 top-up, i should have at least 30% coolant.

Any idea btw the Full & Low marking, is the volume around 1L ?

Definitely hope the gasket is not giving way.
My last ride (honda fit), the coolant reservoir was bubbling non-stop when the gasket give way.
Exhaust leak into the coolant tunnel, i suppose.
Surprisingly, the BlueDevil Gasket sealant really work !!
The best $70 (inc overnite fedex) i've spent !!

[redwine]

For distill water,
are those "Drinking Distill Water" available in Pharmacy/Supermarket good enough ?
i believe most are processed via reverse osmosis rather than Distillation process.
eg.
https://polar.com.sg/polardistilled


Not easy to get industrial grade distill water in my area, esp small amount.

[redwine]

interesting read...


https://www.sparkplugs.com/learning-...-coolant-ratio

[Bonburner]

My concern is the constant water evaporation will concentrate the coolant. Meaning you will have not enough DI water in the mix if you keep topping off with the subaru blue premixed coolant.


Also, I thought the coolant called for DI water (De-Ionized water). Which is different from distilled water. Although, I doubt distilled water will harm the system.

[Ultramaroon]

Originally Posted by Bonburner

I fully understand the expansion of water (and whatever else is in the coolant that can vaporize) will increase pressure in the overflow tank. But there is a hole in the yellow coolant cap to allow for air pressure to release. I personally found that the coolant was evaporating way too fast. Meaning the coolant in the system is not 50:50, more like 45:50 now. If not worse, because I have been regularly topping it off with the 50:50 coolant from subaru. Up until I added an extra bit of sealing to the system.

If both the cap and the reservoir have holes, what exactly does stuffing tape between the hose and reservoir do?

[Bonburner]

Originally Posted by Ultramaroon

If both the cap and the reservoir have holes, what exactly does stuffing tape between the hose and reservoir do?

It reduces the amount of escaping vapors.


edit: so I still top it off, but much less frequently. Maybe one or two times a year.

[redwine]

Just to share....

Under the Owners Manual,
it state SUBARU Super Coolant is a mixture of 50% coolant and 50% deionized water.

Under the Service Manual recommended material,
For coolant dilution purpose, the recommendation is Distilled Water.

[highway7]

Also have disappearing coolant, I bought a jug of the premix and just top it off every once in awhile. Don't believe it's a HG issue, because there's no white smoke, sweet smell, or chocolate milk oil.