REALLY Dirty cooling system - should I flush, or not?

ColoCRDx2 · **Posted:** Fri Feb 04, 2011 12:40 pm

And, as far as flushing the heater core separately before doing a complete system flush......

I'm just saying - it's really easy to do, and from what I've recently learned here and elsewhere - regardless of manufacturer's claims, the HOAT coolant should be changed much more frequently than 100,000 miles. I'm not sure what happens to it when pushed that far.

If I find anything weird when I flush the 06 - I'll report what I find.

.... just my two cents worth

Doug

racertracer · **Posted:** Sat Feb 05, 2011 10:06 pm

Doug, I agree with you on changing the Hoat coolant sooner than 100,000, I was told that 2.5 years / 65,000 miles should be the norm.

ColoCRDx2 · **Posted:** Sun Feb 06, 2011 10:53 am

racertracer wrote:

Doug, I agree with you on changing the Hoat coolant sooner than 100,000, I was told that 2.5 years / 65,000 miles should be the norm.

Yep, I've definitely learned my lesson.

I'm still wondering though - why would the maintenance schedule for CRD's in less severe service recommend the first flush and re-fill at 62,500 miles instead of the 100,000 miles that the severe schedule shows? A misprint, maybe. Did DC forget to recommend the earlier change? :banghead:

Both schedules for the gassers show flush and refill at 60,000 and 102,000 miles?!??

tjkj2002 · **Posted:** Sun Feb 06, 2011 8:36 pm

ColoCRDx2 wrote:

racertracer wrote:

Doug, I agree with you on changing the Hoat coolant sooner than 100,000, I was told that 2.5 years / 65,000 miles should be the norm.

Yep, I've definitely learned my lesson.

I'm still wondering though - why would the maintenance schedule for CRD's in less severe service recommend the first flush and re-fill at 62,500 miles instead of the 100,000 miles that the severe schedule shows? A misprint, maybe. Did DC forget to recommend the earlier change? :banghead:

Both schedules for the gassers show flush and refill at 60,000 and 102,000 miles?!??

In the severe schedule it is figuring that your engine is idling or most likely not shutdown for to long of periods,better for the cooling system.In the "normal" schedule the constant stop/starting of the engine and heat cycles reduces coolant life.

ColoCRDx2 · **Posted:** Sun Feb 06, 2011 9:31 pm

tjkj2002 wrote:

ColoCRDx2 wrote:

racertracer wrote:

Doug, I agree with you on changing the Hoat coolant sooner than 100,000, I was told that 2.5 years / 65,000 miles should be the norm.

Yep, I've definitely learned my lesson.

I'm still wondering though - why would the maintenance schedule for CRD's in less severe service recommend the first flush and re-fill at 62,500 miles instead of the 100,000 miles that the severe schedule shows? A misprint, maybe. Did DC forget to recommend the earlier change? :banghead:

Both schedules for the gassers show flush and refill at 60,000 and 102,000 miles?!??

In the severe schedule it is figuring that your engine is idling or most likely not shutdown for to long of periods,better for the cooling system.In the "normal" schedule the constant stop/starting of the engine and heat cycles reduces coolant life.

Figured it was somethin' like that.

But riddle me this - wouldn't the the constant stop/starting of the engine and heat cycles also reduce oil life? Yet DC recommends 12,500 mile oil change intervals in the "normal" schedule instead of 6,250 miles.

SLS · **Posted:** Mon Feb 07, 2011 3:06 am

Consider the possibility that it could be a combination of hard or acidic water and depleted antifreeze.
The new long life orange and yellow OAT-based antifreeze formulas can typically go 5 years or 150,000 miles between changes.

Aluminum is more vulnerable to electrolytic corrosion than either copper/brass or cast iron because aluminum is a highly reactive metal. When the corrosion inhibitors in the coolant are depleted and the pH of the coolant drops to 7 or below, aluminum becomes a sacrificial anode and is eaten away.

Checking the pH of the coolant with chemically-treated test strips can help you determine if the coolant is overdue for a change. The alkalinity of a typical antifreeze/water mixture will vary depending on the additives in the antifreeze and the ratio of ingredients, but is usually somewhere between 8 and 11. The average for most antifreezes is around 10.5, but when diluted 50/50 with water and added to the cooling system the pH drops to the 8.5 to 9 range. Higher is not necessarily better, though, because some of the new long-life coolants have a pH of only 8.3.

ELECTROLYTIC CORROSION

A different type of corrosion can also occur in the cooling system even if the coolant is in good condition. Electrolytic corrosion can occur if the engine does not have a good electrical ground connection. Voltage from the charging system and ignition system will flow through the coolant to ground, creating electrolysis corrosion that eats away at the metal components in the cooling system. This may eat pin holes into the radiator or heater core and cause coolant leaks. It can even eat away at the inside of rubber hoses and cause them to fail also.

This type of corrosion can sometimes be detected with a voltmeter. Place the positive test lead into the coolant, and touch the negative lead to battery negative terminal or body ground. If the voltmeter shows more than a few tenths of a volt, current is traveling through the coolant and may be attacking the cooling system. Check the engine ground straps for loose or corroded connections. If a ground strap is missing, replace it (or install an extra strap if one is not enough).

The Europeans use less silicates and rely mostly on borates to inhibit corrosion. Their antifreeze also contains no phosphates because hard water can react with phosphates to form calcium and magnesium sediments. The Asians use phosphates but no borates and low or no silicates because they say borates may actually add to the aluminum corrosion problem if the coolant is neglected. The new long life coolants use an entirely different corrosion inhibiting chemistry that uses carboxylate organic acids instead of the silicates, phosphates or borates.

Glad to see this info I had been thinking about changing the coolant. Now I know I'm changing the coolant
I'm looking at some alternatives...........

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AMSOIL Antifreeze & Coolant is compatible with all ethylene and propylene antifreeze and coolant formulations on the market, including DEX-Cool®, Sierra® and Zerex®. It is also compatible with fully formulated diesel anti-freezes and other organic acid technology (OAT) and hybrid organic acid technology (HOAT) formulations.
Super long life fluid - 750,000 miles/7 Years of service in over-the-road trucks & 250,000 mile/7-Year service life in light-truck and auto applications. Essentially nontoxic & biodegradable. Superior performance in all climates. Independent tests reveal AMSOIL Antifreeze & Engine Coolant surpassed standards for metallic corrosion.

REALLY Dirty cooling system - should I flush, or not?

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