Black floaters in antifreeze

Porchhound · October 16, 2022, 10:14:39 AM

During the survey the surveyor dipped his finger in the antifreeze and came out with black globules floating in it. Is this the Death-cool sludge (Dex-Cool) or what else might it be?

mark_53 · October 16, 2022, 10:25:10 AM

oil

Porchhound · October 16, 2022, 10:28:52 AM

How would oil get into the coolant? I'm not sure where the crossover might have occurred.

Noah · October 16, 2022, 10:34:19 AM

Caveat: I am not a mechanic. But I hope it is not oil. That would probably NOT be a good thing and could be (head) gasket problems? I would say flush the system out until clear, then refill with standard green 50/50 coolant and see if it reappears.

mark_53 · October 16, 2022, 11:45:29 AM

Quote from: Porchhound on October 16, 2022, 10:28:52 AM
How would oil get into the coolant? I'm not sure where the crossover might have occurred.

Someone put it in, cracked block, cracked head, head gasket...

Check the color of the oil. If brown (not black) there is water in it.

Porchhound · October 16, 2022, 01:59:33 PM

The other cracked head or block symptoms weren't evident. Compression and overall engine performance, temp, exhaust were good, even at WOT of 3400 RPM and cold start. This C34 was mostly idle over the past three years...only 30 hours logged. I'm wondering if something might be growing in that coolant system.

Noah · October 16, 2022, 02:08:25 PM

Again: empty, fill and flush with water, empty, refill with glycol 50/50, and keep an eye on it — to see if "problem" returns.

Ron Hill · October 16, 2022, 02:20:54 PM

Porch : Do as Noah mentioned. You might want to add another step of using some Prestone Radiator Flush.

If you want to test for oil - take a drop, examine it and see if it floats in a glass of water.

A few thoughts

waughoo · October 16, 2022, 02:54:14 PM

When I first acquired my boat, I did a couple rounds of radiator flush on my cooling system, then drained and refilled with fresh coolant adding a recovery bottle so the system would be free of air. It has been very stable since then. I prob need to do the flush again one more time and then get to a regular schedule of Changi g coolant every so many years.

Jon W · October 16, 2022, 04:07:23 PM

If your coolant is an orange color, then you have Dex-Cool. If you drain and choose to change to the green or yellow color make sure to completely flush the orange out. Supposedly the chemistries have changed so they're all compatible now, but to be safe flush the whole system including the heater loop with distilled water thoroughly.

KWKloeber · October 16, 2022, 06:08:19 PM

Quote from: Porchhound on October 16, 2022, 10:14:39 AM
During the survey the surveyor dipped his finger in the antifreeze and came out with black globules floating in it. Is this the Death-cool sludge (Dex-Cool) or what else might it be?

Seems like the surveyor should know or have an idea?

Capture it and get a mechanic's opinion.

Porchhound · October 16, 2022, 07:15:45 PM

There is a small recovery container (1 qt or so) in the head compartment. Should I replace the coolant through there in order to avoid air...or will that work?

waughoo · October 16, 2022, 08:15:07 PM

The recovery tank works on expansion. When the coolant expands and pressurizes the cap, it will eventually increase pressure above the cap set point pushing coolant out of the tube and into the recovery tank. When the engine cools and the volume of water contracts in the engine, it will develop a vacuum and pull coolant out of the recovery tank. Without the tank, the system will end up with air in it which aids the creation of rust.

mark_53 · October 16, 2022, 08:44:56 PM

Quote from: Porchhound on October 16, 2022, 01:59:33 PM
The other cracked head or block symptoms weren't evident. Compression and overall engine performance, temp, exhaust were good, even at WOT of 3400 RPM and cold start. This C34 was mostly idle over the past three years...only 30 hours logged. I'm wondering if something might be growing in that coolant system.

Well if it's running good that's a good sign. Take a glob out and examine with a magnifying glass. Could be just very old anti freeze.

Porchhound · October 17, 2022, 09:33:57 PM

Went back to the boat today and took samples of oil and coolant. Everything looked okay. When the PO x 2 pulled the engine and replaced the head gasket and oil pan gasket he refilled with green coolant. Interestingly the small overflow container had a few ounces of orange in the bottle. I got a chancer to speak with this guy and he gave me the lowdown on all the upgrades he did based on the recommendations from this site. I'm feeling pretty good about the engine and other systems now.