Do I have a problem, or not?

Following advice given here, I performed a coolant test today, using test strips. The kit says it measures freeze point, nitrites and Ph.

I opened the drain cock at the bottom of the radiator and a pure black fluid resembling engine oil drained out. After swearing a few choice words, I calmed down and examined it more closely.

• It doesn't smell like engine oil
• I don't *think* engine oil settles in the bottom of circulated coolant. Contaminated coolant usually has a milkshake appearance. This does not.
• Swirling it around, it appears to be a black sediment in suspension. The fluid is much thinner than diesel engine oil.
• The engine oil level is normal, just below "F" on the dipstick. The oil color is pure black, not milky in appearance and smells like normal oil.
• I have been running the engine daily, which would circulate coolant and oil.
• Oil pressure is around 80psi when cold.
• Exhaust looks normal, no white clouds...or really any cloud at all. Just a little black.
• Coolant in the surge tank is normal in appearance, lacking the black color that was sampled from the bottom of the radiator.

So, with all that, is this just some sort of sediment or sludge in the bottom of the radiator or do I have a bigger problem?

Now onto the test strip results-

The patch at the top indicates nitrites. This patch read very weak, indicating "charge." This means I need to add SCA?
The middle patch indicates freeze point. This patch seemed to indicate "50" or -37F degrees protection.
The lower patch indicates Ph. This patch looks closer to 8.0 than 7.0, which is squarely in the middle. Not great, but shouldn't be attacking my cylinder liners, right?

Comments on the radiator sludge and the test strip results, please.

Judging by the looks of what came out I think you need to "add" a complete coolant system flush to your list of things to do!

That was always the plan. I was just testing the coolant Ph to see if it was acidic while the truck was sitting and what kind of trouble the cylinder liners might be in.

Cylinder liner cavitation has more to do with engine harmonics forming empty vacuum pockets along the surface of the liner. Unless you're racking up hundreds of thousands of miles your engine will never see that issue. The liner O-rings on the other hand are what you should be concerned about.

The sludge is common, and is a pain to flush. I’d wait until the heat of the summer as it’s much easier to do multiple flush cycles.

That is normal sludge. It just needs a coolant flush. Drain the system, fill with straight water and run the engine for a half hour. Drain the now dirty water. Refill and add some Cascade dish washing soap. Run the engine for an hour. Drain then refill with water and run for half an hour. Repeat one more flushing rinse. Drain then fill with 50/50 mix and SCA. The same rinse method also works after replacing a bad oil cooler. The reason to use dishing soap is it doesn’t foam.

As others have confirmed, the black fluid is corroded bits of cast iron in suspension and a rigorous flushing will clear it. You may have to remove the radiator for individual disassembly and cleaning if your flushing routine does not completely solve the issue,

Rick

Thanks for the solid answers, guys. I've been driving clean, new cars for too long.

rchalmers3 said:

As others have confirmed, the black fluid is corroded bits of cast iron in suspension and a rigorous flushing will clear it. You may have to remove the radiator for individual disassembly and cleaning if your flushing routine does not completely solve the issue,

Rick

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Whoops, I missed this post last night. Very interesting (and reassuring)! Yeah, no problems with removing the radiator. I have to replace all belts and hoses on the truck so I suspect that it'll just be easier with the radiator out of the way.

I wanted to do this stuff this winter because I have nothing better to do, but Jbulach is probably right that it would be easier to build up heat that would dislodge the crud during warmer months. Well, I can still do an oil change and fuel filter replacement and other odds and ends.

You also need to familiarize yourself with the chemical properties of acid/base and also where in the numeric scale is neutral is - for your own knowledge to understand what's happening inside your engine. From what you described a through flush and refill with coolant is what is needed.
Also it would be best to use premixed coolant to assure the water used to blend is also meeting the recommended requirements. It is surprising how people miss that point. Good luck with the cooling system maintenace

PETE BALLARD said:

You also need to familiarize yourself with the chemical properties of acid/base and also where in the numeric scale is neutral is - for your own knowledge to understand what's happening inside your engine. From what you described a through flush and refill with coolant is what is needed.
Also it would be best to use premixed coolant to assure the water used to blend is also meeting the recommended requirements. It is surprising how people miss that point. Good luck with the cooling system maintenace

Click to expand...

I'll read up on that, thanks.

My house is on a well that has mineral laden water, so I sure won't be putting that into the cooling system. If I can't find pre-mixed at reasonable prices, I'll be sure to use distilled water free of minerals.