Cooling system flush questions

1998_K1500_Sub

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Connect the negative lead to ground, and dangle the positive lead in the coolant via the radiator fill neck. See what voltage you get. Less is better, and it better be a small fraction of one volt.

There's two causes of "radiator voltage".
1. Improper grounds. The vehicle electrical system is grounding through the coolant.

2. Worn-out coolant. The dissimilar metals in the cooling system are using the coolant as electrolyte, the metals touched by the coolant are effectively a big battery.

@Schurkey, good stuff here. Be specific about the "ground" reference to be used. Is it:

- a stud on the engine and, if so, where exactly (if it matters)
- a point on the frame
- the battery neg
- (other)

Since the topic is coolant, I would expect the most relevant "ground" reference would be one on the block. Or...

One might use other "ground" references elsewhere in the cooling system, e.g., ground at the radiator or ground at the heater core (front and/or rear heat).

Grounding elsewhere seems irrelevant to the cooling system... maybe relevant to the electrical system, but not cooling.

I assume a DVM with both mV and V scales would be handy.

Finally, dangle BOTH leads into the same pool of coolant (e.g., at the radiator filler neck). THAT reading should be quite close to 0V... and if non-zero then is likely due to the probe's metal tips.
 
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Schurkey

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The link I included uses the battery ground cable clamp.

Connected to the battery, it's testing for electrical system issues causing voltage in the coolant. With the cable removed from the battery, it's testing dissimilar-metal voltage.
 

tayto

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Your correct. I run pink CAT ELC coolant in everything. Mostly because it’s readily available and it fights electrolysis.

As for system flush, I’ve used a lot of crazy stuff. Cascade for dishwashers, mineral spirits, degreaser etc. I would use at your own discretion but my point is not to put much thought into it. Drain, fill, drive repeat a few times and your good.
I've mentioned before on this forum i think, but the best flush product i've found for iron blocks is Motocraft VC9.
 

95burban

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I will try it next time on a small engine. It would probably be to expensive on something that holds 250gal of coolant.
 

Erik the Awful

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Finally, dangle BOTH leads into the same pool of coolant (e.g., at the radiator filler neck). THAT reading should be quite close to 0V... and if non-zero then is likely due to the probe's metal tips.
The only way to get a voltage that way is if your leads are made of dissimilar metals.
 

1998_K1500_Sub

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The only way to get a voltage that way is if your leads are made of dissimilar metals.

Or something really unusual is going-on. I would use that test as a sanity-check.

Measured a voltage? (Y/N)

(N) Good

(Y) Something's amiss. You're not measuring what you wish to measure.
 
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udidwht

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Most coolant now is extended. Prestone recently extended their Green coolant. Used to be 5 year or 150,000 miles. Now it is either 10 year 0r 300,000 miles or 15 years and/or 350,000 miles.

I also see a new labeled one named 'Prime Conv Green' (2 years and/or 25,000 miles)

When I did the coolant in my RV back in 2018 it (standard Green) was still 5 years/150,000. When I saw the same coolant a few years later (with new 10yr/300K) I inquired about it from Prestone. They said nothing had changed with the chemistry.
 
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