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Testing Coolant: Basic Question
I have a basic question related to testing my coolant.
My understanding is that coolant needs to do four things: transfer heat, prevent corrosion, not boil, and not freeze. I have a basic hydrometer that tests only the freeze point. My question is: can I assume the the properties of a coolant, its abilities to do what it's supposed to do, deteriorate at approximately the same rate? So that, if the freeze point is still very low, I can assume that the boil point is still high and the corrosion prevention still intact. Or conversely, is it possible that the deterioration of the properties will occur at significantly different rates? Thanks.
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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles 06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU 91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion 19 Honda CR-V EX 61k mi Fourteen other MB's owned and sold 1961 Very Tolerant Wife |
#2
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antifreeze has little to do with the boiling point protection. the cap does that. higher pressure caps boil water at a higher boiling point.
PURE water will boil slower than water with antifreeze in it. the water wetter products reduce the water particles and make it absorb heat faster... keeps the motor cool.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!! 1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere! |
#3
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Hydrometer tests amound of dissolved stuff in coolant. Freeze and boil temps are dependant mostly on that. As vstech points out, pressure held by cap is predominant boil temp control.
Corrosion protection is via chems in antifreeze, and they get used up over time, hence the periodic repacement. Expect corrosion protection to degrade nearly independently from hydrometer reading.
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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png Broadband: more lies faster. |
#4
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If I wanted to test corrosion protection, how would I do that? With one of those little strips?
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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles 06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU 91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion 19 Honda CR-V EX 61k mi Fourteen other MB's owned and sold 1961 Very Tolerant Wife |
#5
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A rule of thumb is that for every PSI an automotive cooling system is pressurised the boiling point temperature is increased by one degree Celsius...
Read more than you'd ever want to know about antifreeze here:- http://en.wikipedia.org/wiki/Antifreeze
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1992 W201 190E 1.8 171,000 km - Daily driver 1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone 1965 Land Rover Series 2a Station Wagon CIS recovery therapy! 1961 Volvo PV544 Bare metal rat rod-ish thing I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior Don't leave that there - I'll take it to bits! |
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The manufacturers apparently have a different opinion. Zerex, for example, claims that a 50/50 mix of G-05 and water has a boiling point of 226 degrees F at standard atmospheric pressure.
That's an interesting claim, since 100% G-05 boils at 325 degrees F. Water particle reduction. Now that's an interesting concept!!! |
#7
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Generally the high boiling point of water and its high heat capacity is due to the hydrogen bonding between molecules. However, Tango, you are correct that the addition of antifreeze increases the boiling point of water. This is due to the colligative properties of mixtures and the fact that anti-freeze has a higher vapor pressure than water. The addition of anti-freeze increases the overall boiling point, despite reducing the hydrogen bonding of the water molecules. I hope no one minds my geeking out here. http://www.peachparts.com/shopforum/images/icons/icon10.gif |
#8
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Never Assume ANYthing WHEN :
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You use a VOM to check the corrosion protection ( as per the FSM )...
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1980 240d , chain elongation, cam marks reference: http://www.peachparts.com/shopforum/showthread.php?threadid=10414 http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html evap fin cleaning: http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator A/C thread http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html |
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Incorrect. Freezing point depression and boiling point elevation are colligative properties and are solely due to the presence of other molecules/ions/atoms being dissolved in water. If you dissolve ANY substance in water it will both lower the freezing point and raise the boiling point.
Correct. The phase diagram of water (and every other substance I can think of) reveals that the boiling point increases with system pressure. The exact relationsip is described by the Clausius-Clapeyron equation. Quote:
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Incorrect. Anti-freeze does not significantly alter hydrogen-bonding. Incorrect. The size of these molecules size does not appreciable change because of the presence or absence of inter-molecular forces from other molecules. ------------ |
#10
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__________________
1992 W201 190E 1.8 171,000 km - Daily driver 1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone 1965 Land Rover Series 2a Station Wagon CIS recovery therapy! 1961 Volvo PV544 Bare metal rat rod-ish thing I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior Don't leave that there - I'll take it to bits! |
#11
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#12
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You can buy a kit with test strips to test coolant, I keep them on-hand for testing. They are diesel-specific, the simple 3-way test: pH, Nitrates, and freeze-point, there are also 5-way strips.
The problem is that I don't know if these are accurate to the needs of a Mercedes-Benz automobile, so even if they indicate good there might be something that Mercedes diesels need that isn't being tested (or indicated to the proper Mercedes level). The kits only have about a 1-year shelf life, less than the life of the coolant in your car so if you do wish to play with the strips buy the 3-strip packet from NAPA instead of the more common 50-strip bottle$. The easiest IMO is to just change at the factory interval with the proper G-05 coolant and distilled water (per FSM). On the 124s there is a new pressure tank available that has a silicate pack in it (aka: coolant filter in the H-D world) to extend the useful life of and stabilize the diesel coolant, I don't know if the same is available for your 126.
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Gone to the dark side - Jeff |
#13
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The "cavitation inception" I have heard of described as a nucleation source. That's why we put boiling chips in a beaker to control the boiling. It is an entirely separate process than the colligative mechanism discussed above. |
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I do not know how one would directly measure increased or decreased hydrogen bonding. I do not know if the IMF (inter-molecular force) of hydrogen-bonding (it's not a bond but an interaction) is measurable with spectroscopy. It's not an area that I have explored. So I am not aware of anyone showing an increase/decrease in hydrogen bonding by doing such-and-such. Surface tension is a surface phenomena. It is understood by the presence or absence of certain chemicals that are at the surface. The term surfactant means surface active agent. It's very possible to add a chemical to water and have it present in the part per million level in the solution and yet be a thousand (or more) more concentrated at the surface. I believe I understand the thinking of the statement: .. decreased surface tension indicates decreased hydrogen-bonding ... It is not an accurate description of what is occurring. Sorry. It's not a personal attack I've just spent a lot of time studying inter-facial phenomena. Quote:
Last edited by sjh; 04-14-2011 at 05:26 PM. |
#15
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That's interesting. I wonder with the difference in AF composition today versus when the FSM was written if that is still valid. Could you briefly describe the FSM procedure and values? Thanks. |
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