Simple question about coolant recovery tank

[thinwater]

Originally Posted by Djarraluda

Key issues are the difference between Ethylene Glycol, common coolant product, or Propylene Glycol, food safe antifreeze for ice cream etc.
If mixed, you get a funk, jelly like strands form that is not good in the water passages!!
Do not taste test, ethylene glycol will damage your liver!
We used to have a commercial ethylene glycol manufactures (distilled) for our business and chose the colour. It is just a dye.
Ethylene glycol will oxidise in use, any exposure to air and it degrades, becomes acidic. That is why you change coolant. One other post here talks of measuring PH, this is the check for degradation.
Most coolants also contain ph modifiers to prolong the life.
Best recommendation is to test the coolant. Then flush and renew so you know what you have, a new baseline to work with.
Roger

a. EG vs. PG. There is very little difference in physical properties. You can use either in any engine coolant formulation. There no is tendency of PG or an EG/PG mixture to get stringy. You misinterpreted something. In the past, some of the early additives did not play well together.



b. EG and PG can both degrade with air (this is why you use an expansion tank--it keeps the air out of the system). However, in a marine system, the reason AF is replaced is risk of seawater contamination. Ask either Yanmar or Mack Boring. Replace every 1-2 years. Based on hours and thermal breakdown, it would last 10 years. But it will likely fail for something else first. A boat is not a car.



c. The OAT add pack is a natural pH buffer and is formulated to function closer to neutral pH than the traditional borate/phosphate/silicate types. The pH will run lower than traditional AF, so don't go by old pH advice. Anything >8 is just fine.

[a64pilot]

Originally Posted by thinwater

I do NOT recommend flushing unless the system is clogged with scale. I was part of the ASTM committee, talked with the head engineering guys at the big manufacturers, and none were fans of flushing. It is easy to do more harm than good.

Now when you say flushing can easily do more harm than good, I assume your talking about a chemical flush and not a fresh water flush?
My when new to me 27 yr old engine had some rust in it and needed to be removed somehow, and installing the Prestone flush kit which is nothing more than a T in a heater hose that a garden hose will connect to and a couple of fresh water flushes, it removed nearly all of the rust.
At least I think it was rust, it looked like rust anyway.
Point is that I think there are many engines with rust etc in the coolant that a just drain and refill won’t remove.

However for a new engine, by all means drain and refill, it’s what I have done in our little cars that I got new anyway as there is never any rust to engine with.

[EthanC]

Originally Posted by thinwater

I spent 25 years in the coolant formulation business (manufactured glycol, tested coolants, one patent).


a. The current Dexcool is not the original Dexcool. It has been subtly reformulated to get around a few early short comings. So for get the old horror stories, they no longer apply. It's a good product, for both gas and diesel.


b. You don't need to flush unless you are dramatically changing chemistries. Just change what you can.


c. The marine change interval is driven not by the coolant wearing out, but by the risk of seawater contamination. So for get longlife and change it every few years.



d. Use only water of equivalent quality to what you would use in batteries (there is an ASTM spec). Not tap water and not from the watermaker.

Question:



The Red coollant it is OTC also? If yes it can be mixed with Dexcool?


Thank you.. Ethan

[vic008]

To get rid af any trapped air, I found a clear plastic hose, about 1m long, jammed well enough into where the the pressure cap normally sat. Filled it with water, ran motor for 5 min, then there was a big burp,, hot water shot out the top of the hose, and I dont know but I think she was cleared of air.

[Steve DAntonio]

If the boat is new to you, there's a very strong argument for flushing the system and replacing the coolant. Ideally, coolant should be replaced every two or three years regardless of engine hours.

Coolant recovery bottle fluid level should be at the COLD level when...cold, leaving room for it to expand when it heats up. The level to which to coolant moves when hot and cold should be constant. If it returns to a lower COLD level, you have a leak, if it rises to a higher HOT level you are either overheating or fluid is leaking into the system, possibly from a water heater. Recovery bottles are valuable indicators for coolant issues, something you can easily glance at and know right away of there is an issue. More on coolant recovery bottles here https://stevedmarineconsulting.com/t...overy-bottles/

Unless you have no coolant available, topping up should be done using the same mix that's in the system. Barring that use distilled water and barring that tap water.

[wsmurdoch]

Steve, I have two questions about your linked article.

Two thirds of the way through is the sentence, "For systems not equipped with an expansion tank, an air void is maintained at the top of the expansion tank when the engine is cold, into which coolant expands when the engine heats up." If there is no expansion tank, how is there an air void in the expansion tank?

The second and more real question is about my coolant system. I have a 1988 Yanmar 3HF35F engine. It supplies hot coolant to both a water heater and a Heater Craft 'bus heater' in the main cabin. The two are piped in series; the 'bus heater' first, then the water heater. The 'bus heater' is below the engine, and the water heater is above. In the return line between the water heater and the engine, a head tank is teed into the system. Both the head tank cap and the engine heat exchanger cap have overflow hoses that are teed together and go to the plastic overflow bottle.

Now my questions... Should both overflow hoses go to the overflow bottle or should only one? If only one, which one? If only one, what should be done with the other? If both, which cap should have the higher relief pressure, or should they both be the same? Is it more important to burp air from the engine heat exchanger or from the expansion tank?

Thanks Steve,

Bill

[thinwater]

Originally Posted by EthanC

Question:

The Red coollant it is OTC also? If yes it can be mixed with Dexcool?

Thank you.. Ethan

There are no color codes set by regulations or industry standards. It's been discussed but has failed to gain traction. Any answer would be a guess. Sorry.

[thinwater]

Originally Posted by a64pilot

Now when you say flushing can easily do more harm than good, I assume your talking about a chemical flush and not a fresh water flush?
My when new to me 27 yr old engine had some rust in it and needed to be removed somehow, and installing the Prestone flush kit which is nothing more than a T in a heater hose that a garden hose will connect to and a couple of fresh water flushes, it removed nearly all of the rust.
At least I think it was rust, it looked like rust anyway.
Point is that I think there are many engines with rust etc in the coolant that a just drain and refill won’t remove.

However for a new engine, by all means drain and refill, it’s what I have done in our little cars that I got new anyway as there is never any rust to engine with.

There is nothing wrong with freshwater.

Rust is a problem. The ONLY way that can form in a less than 5 years is if there is an air leak (probably blown head gasket) supplying a gross amount of oxygen, salt contamination of the coolant (HE leak), or an electrical problem (stray current in the coolant--not as rare as you would think).

With modern coolants, iron corrosion is basically zero. PPM in the coolant at most, and never anything you can see... unless you are running a wet sleeve engine and not using a cavitation chemistry (HD coolant).


Of course, 27 years is a while, and who knows what the PO did!

[chrisr]

Originally Posted by thinwater

I spent 25 years in the coolant formulation business (manufactured glycol, tested coolants, one patent).


a. The current Dexcool is not the original Dexcool. It has been subtly reformulated to get around a few early short comings. So for get the old horror stories, they no longer apply. It's a good product, for both gas and diesel.


b. You don't need to flush unless you are dramatically changing chemistries. Just change what you can.


c. The marine change interval is driven not by the coolant wearing out, but by the risk of seawater contamination. So for get longlife and change it every few years.



d. Use only water of equivalent quality to what you would use in batteries (there is an ASTM spec). Not tap water and not from the watermaker.

can you explain a bit what is the problem with using water from the watermaker to top up coolant. i thought this (being very pure h2o) would be highly suitable ?

cheers,

[Steve DAntonio]

Originally Posted by wsmurdoch

Steve, I have two questions about your linked article.

Two thirds of the way through is the sentence, "For systems not equipped with an expansion tank, an air void is maintained at the top of the expansion tank when the engine is cold, into which coolant expands when the engine heats up." If there is no expansion tank, how is there an air void in the expansion tank?

The second and more real question is about my coolant system. I have a 1988 Yanmar 3HF35F engine. It supplies hot coolant to both a water heater and a Heater Craft 'bus heater' in the main cabin. The two are piped in series; the 'bus heater' first, then the water heater. The 'bus heater' is below the engine, and the water heater is above. In the return line between the water heater and the engine, a head tank is teed into the system. Both the head tank cap and the engine heat exchanger cap have overflow hoses that are teed together and go to the plastic overflow bottle.

Now my questions... Should both overflow hoses go to the overflow bottle or should only one? If only one, which one? If only one, what should be done with the other? If both, which cap should have the higher relief pressure, or should they both be the same? Is it more important to burp air from the engine heat exchanger or from the expansion tank?

Thanks Steve,

Bill

First question, that was a typo, it's been corrected (thanks for catching it).

Second question, the lower cap should never open or vent once a remote expansion tank is installed, that's usually accomplished by installing a higher pressure cap on the lower expansion tank, again ensuring it will never open.
This article covers the subject of remote expansion tanks in more detail https://stevedmarineconsulting.com/water-heater-primer/

[Steve DAntonio]

I routinely encounter visible rust inside cast iron expansion tanks that are not equipped with recovery bottles. In that case, the contracting coolant leaves an air bubble in the expansion tank, allowing rust to firm. This is another case for recovery bottles, as the air bubble is eliminated.

[wsmurdoch]

Thank you, Steve. I understand.

The Yanmar shop manual gives the engine cap specification to be open above 12.80 lb/in^2 pressure and also open below 0.71 lb/in^2 vacuum. The head tank cap is marked 13 lbs. I suspect that only the engine cap passes coolant because when opened with everything cold the head tank is always 3/4 full and when the engine is operating the overflow bottle level rises and falls with the engine temperature.

I'll buy new caps and straighten it out at the next coolant change.

Again, thanks,

Bill

[Steve DAntonio]

Originally Posted by Steve DAntonio

I routinely encounter visible rust inside cast iron expansion tanks that are not equipped with recovery bottles. In that case, the contracting coolant leaves an air bubble in the expansion tank, allowing rust to firm. This is another case for recovery bottles, as the air bubble is eliminated.

Here's a textbook example...