Floaters in the cooling system- What are they? (1 Viewer)

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GRM

Finding new adventures in old jalopies.
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This morning I went to pull my FJ40 out of the garage and noticed a small coolant puddle under the truck. I checked to find the coolant reservoir low, and filled with some kind of particles.

When I popped the radiator cap, the system was under pressure (despite not being driven for 4 days).

I found the same floating particles in the radiator too.

Does anyone have any idea what this could be? For reference, the engine is a 4 year old 2fe with around 3,000miles on it.
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Does it stick to a magnet? (probably shouldn't float it it's metal anyways..)

My first guess would be paint. How much overspray was inside water jackets, etc. when it was rebuilt?
 
Could be rubber from old hoses.
 
Or maybe rubber from new hoses like filings from the cutting of them. Paint sounds likely also.
 
Doesn't hurt to check with a magnet. Magnetite is a form of "rust" (Fe3O4) that forms in low O2 environments.

Might also be copper oxide, which can be black as well.
 
I just tossed a magnet in the coolant and was surprised that many, but not all, the particles were attracted to it.
When wiped on a paper towel, they feel like grease, or old rubber.

What confuses me the most is that this is new as of the last 2 weeks.

Maybe the coolant I used over the summer is the wrong stuff for this truck and causing corrosion?
 
New radiator and all new hoses with the rebuild.
 
Magnetite in boiler tubes is a good situation. It forms a protective layer on the water side of a steel tube, and minimizes corrosion rate. Something has to form on the cast iron block water passages, and IMO this is okay

Bad news is hematite Fe2O3, red rust, and we all know what that is.

I think anything immersed in ethylene glycol is going to feel greasy.

@GRM , you missed this question: "Was the rad cleaned or flushed after the rebuild of the motor? Could be old crud breaking loose."?
 
How old is the water pump?

Personally, I'm pretty lazy, and would just keep driving the thing till I found something broken (like water leaking from the water pump seal).

But I guess you could try a pressure test. I bought one of these late last year:
Amazon product ASIN B0002SRGWU
Hooked right up and showed me that what I thought was a leaky hose actually the seam in my radiator. It might show something useful for you, it might not.
 
@GRM , you missed this question: "Was the rad cleaned or flushed after the rebuild of the motor? Could be old crud breaking loose."?
I didn’t miss the question. I put in a new radiator with the new engine.
How old is the water pump?
The Aisin water pump was installed 4 years and 3,000 miles ago with the new engine.
 
It could be coming in thru the overflow bottle. Its exposed to the air, and has a ring around the inside. Have you ever used tap water to top it off?
 

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