Calculating Alde glycol quality with simple annual gravity drains and refills

RMo

I’ve read (or skimmed) most everything I could find on changing glycol in the T@B and see a mix of great DIY ideas, high costs from dealers and lot of hesitancy to dive in and try a DIY solution.  Throw on top of that the unknowns about the need to switch to the new Rhomar fluid and it can cause analysis paralysis or just plain denial of the need to do anything – at least it did for me.

After getting through the denial phase and considering the uncertainty of the need to do a complete flush and switch to a new fluid, I thought I could easily handle a gravity drain of the system through the drain plug, and a refill of the system.  I wondered, however, just how effective this would be.  To figure this out, I drained what fluid I could from the system via the rear drain -- managing to remove 6.5 quarts of glycol (2019 T@B 400).  Using a total capacity guestimate of 15 quarts, I calculated that each refill done in this manner would leave 57% of whatever fluid was in the system to begin with and add 43% new fluid each time.   Assuming an exchange of this type each year and starting with 2-year-old fluid, the average age of the fluid just prior to the yearly exchange starts at 2.0 years (prior to initial exchange) and slowly rises to and average age of 2.3 years prior to the 10th annual exchange.

I’m not certain that the average age of the fluid is a precise indicator of its quality, but  the calculations gave me the confidence that I could do a simple drain and refill each year without much risk of damage to the system.  All this, of course, pending any new info on why Alde is recommending a new type of fluid, and pending my need to tinker with pumps, shop vacs, low-point drains and all the other great ideas that are posted in this forum.

For me the partial exchange approach is at minimum a short-term solution that takes little skill or time, and the only cost is the fluid itself.  I’d love to hear any thoughts, especially on the assumption that the average age of the fluid is a reasonable indicator of quality.

webers3

My thought on Alde fluid exchange is this, or rather a question; of those who promote annual or bi-annual fluid exchange, or whatever the frequency, how many exchange the coolant in their automobile in the lifetime of their auto and how often?

Verna

@webers3, I was going to try to explain, but I realized I don’t have the terminology down pat to explain. If you read this discussion ,starting on page 5 (pages 1-4 are from 2016 to 2019), there is a lot of great information in it. No, I do not understand everything I know about the glycol, but there there are others who do https://tab-rv.vanillacommunity.com/discussion/2665/changing-out-the-alde-fluid/p5

webers3

@Verna Yes, I've read that discussion, the question remains

Ricky

Interesting 

qhumberd

The reason that pushed me out of my comfort zone and made me drain flush and refill rather than just drain and partially refill was the issue of corrosion on the convectors, documented by more than one. There seems to be a good rationale that this is a chemical/electrolytic issue with the Alde. The comparison with automotive cooling systems is less compelling for several reasons, not least of which is the difference in the glycol mixtures and the sealed pressurized design. So for me the unknown factor is what additives in the glycol are there and how long do they prevent corrosion? When they degrade what is effect of mixing fresh glycol? None of these are known at least by me. So learning how to drain and flush and refill my system seemed less risk than assuming that dilution and mixing of old and new glycol would prevent problems. Since I am at least starting with a fresh fill every 2 years. And it was much easier than I imagined thanks to @ScottG and others.

ScottG

The corrosion issue that surfaced in several T@Bs earlier this year was certainly a motivator to do a more thorough job with the glycol exchange. However, I'm not completely convinced that the crevice corrosion evident on the convector stubs was the result of neglected or degraded glycol.

Now that I've done a full exchange on mine (albeit with the previously recommended century fluid), I'll be curious to see how those stubs look in another year or two. Unlike some other owners, I did not take any addition steps to protect the convectors other than cleaning up the existing deposits as best as possible. 

tphaggerty

So I may have missed it, but is there any information about mixing the old and new glycol formulas. I am 5+ hours from any dealer that I would be comfortable doing the flush and replace. But, following RMo’s plan sounds like a good idea, maybe better if you could use the new formula to gradually remove the old. Just a thought…. 

Sharon_is_SAM

If you mean “new formula” as in Rhomar - you can not mix the Century with the Rhomar.  If you change to the Rhomar, you must drain the Century then flush with distilled water before refilling with the Rhomar.

Verna

@tphaggerty, under no circumstances do you mix the two kinds glycol. This warning comes with both types of glycol.