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Normal Coolant Evaporation Rate with Recovery Tank?
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Post Normal Coolant Evaporation Rate with Recovery Tank? 
What amount of coolant evaporation is considered normal in an well working RECOVERY TANK TYPE cooling system (pressure cap is on radiator, coolant recovery bottle under atmospheric pressure, e.g. like our trucks), that has otherwise no external leaks? This question has been on my mind for a while and I can't seem to find any answer to it.

There is an SAE Paper 2015-01-1655 that seem to deal with this subject, but I can't get access to it unless I pay some ransom. I could only see the preview and the preview suggest that there IS coolant evaporation which in addition may be influenced by recovery tank design.
https://www.sae.org/publications/technical-papers/content/2015-01-1655/

I understand coolant use may be dependent on many conditions. I'm really looking for an answer to coolant evaporation rates on healthy vehicles with no other leaks than perhaps at the weep hole of the water pump. In other words on a vehicle in new condition.

What are the experiences?

...

There is a specific reason that this question is of my interest:
Unlike before, now apparently more and more manufacturers start using High Pressure DieCast Method to manufacture their engine blocks. Using this method, they are able to produce lighter blocks with thinner walls. However the system does not come without it's issues. Porosity of the cast is one issue. As a result casts are checked for leaks those that are determined leakers will be treated/sealed with various methods. Which begs the question how effective such treatment is and how long is it good for?

As an example, here is one of the companies that offers Casting Impregnation Services:
https://www.cmf-us.com/Home/CastingImpregnation
Check out some of their links on the website as well.

So I would like to see some normal rate of evaporation established (again for 'semi-open' RECOVERY TANK SYSTEMS), so that we have a comparison.

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Another good example for die-casting porosity issues and sealant repair:
https://www.godfreywing.com/blog/3-types-of-die-casting-porosity

Video about the sealing process:
https://vimeo.com/225297533?__hssc=163776992.1.1533175607023&__hstc=163776992.d2ae19b5eb9230426ee4a48afb003df7.1533175607023.1533175607023.1533175607023.1&__hsfp=1023962018&hsCtaTracking=9c8fe39c-0a37-4ca5-a5f4-5481009ca841%7Cb1dbc7f2-606e-4f37-b27e-8654673279dd

I don't quite understand how setting the entire part uniformly under vacuum would draw the sealant into the porosity areas. I would more understand if certain areas of the part are under vacuum while others that contain the sealant are not.

Another great read on the topic:
https://www.starrapid.com/blog/porosity-in-pressure-die-casting-and-how-to-control-it/

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1999 Tahoe 4x4 wrote:
I don't quite understand how setting the entire part uniformly under vacuum would draw the sealant into the porosity areas. I would more understand if certain areas of the part are under vacuum while others that contain the sealant are not./


What I got from the video is that if they just dip the part in the sealant, the sealant will seal air inside the fissures, which means you have an incomplete seal. An incomplete seal would eventually rupture under use. Just dipping would extend the life of the part, but not by much and when it fails it would fail the same way it would if untreated. What they are doing by first pumping all the air out is removing anything inside the fissures, allowing the sealant to fully penetrate the fissures. The sealant is pumped in under pressure, so it gets as far inside the fissures as is possible.

Of course, I could be wrong, which seems to be the norm these days...

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In retrospect, I see I started this thread with the wrong title. It should have been something along the line of "Porosity and Remedy in Modern DieCasting of Engine Blocks" or alike.

Speeder wrote:
Of course, I could be wrong, which seems to be the norm these days...

No worries. What you wrote makes sense.

Although I would expect the sealant to penetrate the cavities already to a high degree via capillary effect as well. Perhaps the use of vacuum is key for a complete penetration.

By the way, it would also be interesting to know how permanent such sealants are. I suppose manufacturers claim them to be effective for a "lifetime", but as we know that definition can vary widely.

A great video of a Totoya visually leaking oil because of porosity of the cast:
https://www.youtube.com/watch?v=TRjWwFk_W48

From what I read, Toyota has already used High Pressure DieCast engine blocks since 2000 in their AZ engine line:
https://en.wikipedia.org/wiki/Toyota_AZ_engine
[..."The cylinder block is an open-deck, midi-skirt die-cast aluminium type with cast-in iron liners and a die-cast aluminium lower crankcase"...]

The 2004+ Mercedes M275 engine seems to be High Pressure DieCast as well. As a matter of fact, from what I read, THESE DAYS most open deck engine blocks (which seems to be nearly all new engines) that have cast in cylinder sleeves are made via High Pressure DieCast.

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After seeing that leak, I would bet that owner is not too happy. Seems to me the potential cost to repair must not outweigh the cost savings to manufacturers. That is interesting.

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