Feel free to believe that the world is flat.

The whole mainstream automotive world believes that antifreeze becomes corrosive when old.

The onus is on you to prove them wrong.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

I can find thousands of sites on Google that back me up.

Here's one section from a Ford website.

"Even though your coolant in your vehicle is green, it may be sending you the wrong signal. Additives to protect the cooling system may have been depleted and the green color remains. Ethylene Glycol (antifreeze/coolant) will turn acidic when buffering ingredients have been depleted, acidic coolant becomes extremely corrosive and components such as the waterpump, cylinder heads and timing chain covers, can become pitted or worn prematurely and lead to costly repairs. That is why your cooling system needs to be power flushed every 2 years or 30,000 miles."

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

Here's another site:

http://www.molderschoice.com/pdf/Page145BUndilutedEthyleneGlycol.pdf

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

Acidic corrosion happens when the coolant drops the pH level below 7.0, which happens when there are more positively charged hydrogen ions than negatively charged hydroxide (OH-) ions. Technically, only H30+ (called hydronium) ions exist, because free hydrogen ions quickly combine with H20 molecules to form H30+ ions. The result of this excess is that metal surfaces are corroded with pits as the positive ions rip up and then combine with atoms from metallic and other surfaces.



The pH level is actually defined in an interesting manner. It is defined as the negative log10 of the moles of H30+ ions per liter of water. Water naturally ionizes like this: H20 -> H30+ + OH- about once for every 107 molecules. So, in one mole of pure water, there is about 10-7 moles of H30+. The more H30+ ions you have, the lower the pH level becomes. The pH scale of 0...14 relies on the fact that the product of H30+ and OH- concentrations is always 10-14. If you are interested in a bit more detail, try this page on pH Scale. There are some details here that a doctorate in chemistry (such as our staff member pHaestus) could share, but, thankfully, those details are mostly irrelevant to our discussion.

Moles of Hydronium Ions in One Mole of Water
pH Level

100 Moles = 1.0
0 - Perfect Acid

10-1 Moles = 0.1
1 - Very Acidic

10-2 Moles = 0.01
2 - Lemon juice

10-4 Moles = 0.0001
4 - Wine

10-7 Moles = 0.0000001
7 - Neutral (neither acidic or basic)

10-10 Moles = 0.0000000001
10 - Detergent for Washing Clothes

10-12.5 Moles = 0.00000000000032
12.5 - Household Bleach

10-14 Moles = 0.00000000000001
14 - Perfect Base


In theory, you will see corrosion start when the pH level drops below 7.0. However, copper and aluminum will typically form a thin hydroxide coating that is stable until pH levels drop below 4 or 5. To complicate matters, however, you can go too far in the other direction too. Making the coolant too basic (called an alkaline pH level) can cause corrosion too. A strong base can strip the protective aluminum hydroxide layer that forms on an aluminum surface nearly as easily as a strong acid. And in situations where metal oxide coatings do not form, a strong base can actually be even more corrosive to elemental solid than an acid.

Coolants typically perform best when the pH level is from 9.0 to 11.0. As the coolant ages, it becomes more acidic and starts attacking the metal surfaces, so manufacturers add buffering chemicals. These buffering chemicals (usually borates and phosphates) absorb the acidity as it forms, preserving the safety of the coolant. The buffering capacity of a solution is known as alkalinity. You do not need buffering chemicals if you change your coolant before it becomes too acidic, and many cheaper brands of antifreeze-style coolant skip the buffering chemicals to save money.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

has anyone been amused by Porsche's coolant `fill for life ` recommendation?

Yeah right... given best performing Porsches were air-cooled and atmospheric air can be replaced only by moving away :p

~Nautilus

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1990 260E Sportline (that's 300E 2.6 for our American friends) -> sold
2001 E320 4Matic Elegance -> my Dad's daily drive
2005 Seat Leon FR 1.8T

28 years ago I bought a new Chevy Blazer. To date, I have never changed the radiator and did however change the AF 16 years ago. The Blazer has a new body, mostly, on it and about 150K miles. So when should I change the acid/caustic AF along with the radiator? I am confused as this truck runs perfectly as it was like new. Perhaps Chevy really knows their stuff when it come to radiators. What say you?

Good for you, Peter.... but I would say your experience is the exception, not the rule. I've bought many a used (5 year old) car where the coolant was never changed and brown in color, only to fail a bit later from corrosion rot.

I have seen data from Ford Motor Co where they plot corrosion protection versus miles for the green stuff. Right at 30,000 miles it crosses the corrosion threshhold.

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95 E320 Cabriolet, 159K

Strange I missed this post.

It's also strange how some folk get away without maintaining anything. I have a college buddy that was/is that way. He can take a car and universally wear it out having almost no problems until it is a useless POS after 10 years. Since I have know him he has done that to two MBs and a couple Nissans. Other than never maintaining a car, he is probably gentler with it than any one I know outside my dad.

Such stories can be interesting because they are UNUSUAL. I decided years ago that he got such use out of his cars only due to his inordinate ease of use (He slows up as he aproaches green lights - I can't ride with him as he drives me nuts).

Anyway, for those who enjoy their cars and aren't up for Russian Roulette, factory procedures are a good place to start with any personal modifications.

As it turns out I know a bit about corrosion (BS Metallurgical Engineering UofF 1974). Basically it isn't the antifreeze that makes the acid it is the water. It WILL happen unless the antifreeze stops it. The way it stops it is the basis for differences in coolants as everything we have talked about is ethylene glycol. It is the corrosion inhibiting package that changes. Original "green" coolant used phosphate and silicate ions to tie up the process. It turns out that these ions find something to grab onto and plate out as solids over time. It turns out that the corrosion properties aren't linearly related to the ion concentration. It takes some level for them to work and it just stops beneath that level. Thus one doesn't need to get it all out if one changes it regularly adding to the package enough to maintain that threshold.

It turns out that the solids eventually plug raditors and the ions used turn out to embrittle many plastic and rubber components, including hoses, radiators, and waterpump seals. As a result a different technology was created called OATS, organic acid technology. These huge organic molecules somehow protect the metal from corrosion and unlike their name the mixture is stabilized to a "basic" mixture of pH 7.5-11, see:
http://www.valvoline.com/pages/products/product_detail.asp?product=10

The key to making all these antifreezes work is the right amount of additive package in the system. This is the only reason you can mix them. If you had 25% oats and 25% ions and 50% water you would have too dissimilar additive pachages that would not help each other and thus both wouldn't work.

These OATs or HOATs (add hybrid) are all low silicate low phosphate. Almost all are "No phosphates" but G05 has in the area of 250ppm silicates and thus the difference between it and the 5/150 coolants (Dexcool) which have "No silicates"

As a sidebar some Jappanese cars are using water pump seals that are quickly embrittled by even low silicate coolants and require "no silicate" compounds. as such it is common for good maintenance with improper coolant to result in a waterpump failure about a year later.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Common sense from the "modern Mordor" which Romania is:

All fluids are far damn cheaper than rubber & plastic parts, and light years away from the cost of major parts, leave aside the labor costs. For this reason, fluid change intervals recommended by factory have to be attended. And a proverb says "you can't foresee from where will the rabbit jump" - the radiator may live for a quarter of a century like new, yet water pump gasket (or, God forbid, cylinder head gasket) can go to hell when you expect less. Or a hose, for the matter.

That's why here we change coolants each spring & autumn, adding 50% AF in the autumn and less or not at all in spring, flush the brake fluid when it becomes black, change the oil & oil filter when specified, add oil additives after a number of oil changes, complete power steering fluid when low etc. Better give a few bucks away than risk a $5,000 engine rebuild.

BTW there was a story (urban legend?) on Tori Spelling, who was seen pouring a $6 bottle of mineral water in the radiator of an E30 series BMW. Given the risk of an overheating in Californian weather, I understand her... just that I use distilled water on my M-B

~Best regards,

Nautilus

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1990 260E Sportline (that's 300E 2.6 for our American friends) -> sold
2001 E320 4Matic Elegance -> my Dad's daily drive
2005 Seat Leon FR 1.8T

I'm sure everyone has seen the Xerex G05 that is supposed to be a Mercedes golden coolant equivalent. But yesterday at the parts store I see Prestone has finally jumped on the bandwagon with something similar to G05 !! How confusing to the average joe. Prestone makes the normal green, low toxic, dexcool (orange) and now this new stuff.

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David McDonald
1981 240D
1985 300D (wrecked)
1985 300TD 365,000 miles
1969 Mustang Fastback

It seems to me that everyone knows the problem (acid) but no one has told how the average person can test for this acid. Well, here is a little trick I learned a few months ago. Set a digital meter to mv and put the positive probe in the coolent and the negative probe to ground (engine, body or battery). If you get over 300mv (.3v) then change your coolent. If it is under 300mv than everything is fine. I would still change the coolent every 2 years but the DVM trick will help if you forget, or if you aquire a used car and don't know the history of the car.
I didn't believe this at first but after doing some testing on my own cars (some maintained very good and some very bad) I proved to myself that it works.

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84 500 SEL (307,xxx miles)

The litmus test for reserve alkylinity is only valid for conventional "green" antifreeze, so they are not valid for pure organic formulations such as Dexcool, or hybrids like MB brand or Zerex G-05, which is the same formulation as MB brand and approved for all DC vehicles.

Your best bet for coolant system longevity is to replace the antifreeze at the manufacturer's recommended change interval, which is every three years, regardless of mileage, for MBs.

Duke

Paul- thats a cool trick. I am going to have to try that out sometime.

As far as never having a problem for lack of maintaining a vehical,unless you actually take apart the radiator and insepct some internal passages you cant very well verify that its still in great condition. I have seen plenty of ATV's run with the worst looking motor oil you have ever seen. But they still ran, were they running good? Good enough, but surely not what they could be doing with proper oil and change intervals. I guess its just what level of performance you consider acceptable.

Also how do you think you are going to be proved wrong? Most likely on the side of the road with the hood up......

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88 300E
03 911 C4S
2008 Triumph Speed Triple

My pics --> www.BrettAdamsDesign.com

What we have here is a good old fashion peeeeeeeeeeing contest.

Can't we just all get along

It's your ride do as you want. I say do as LarryB says change it hot change it often.. Has all this acid talk brought us back to the 60's LOL

MR. LUCKY

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1997 E420 White