Grit in Coolant and System

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Mar 3, 2015
Lonely Nevada
In the process of installing my new radiator. Drained the coolant and upon inspecting it for whatever.. found that it is full of sand-like grit. Well maybe a little finer than sand. Also found it pooled up in the low part of the hose elbows. The only thing I can think of.. that it is rust from the cooling passages in the block. However I inspected the previous coolant when it was drained in prep for my first radiator replacement. No grit! Possibly it was hiding in that replacement radiator. I flushed it before it before it was installed. However I didn't really put a lot of effort into it as it was a brand new radiator.

SO other than rust in the block.. any ideas as to where the grit came from? I did't really need to pull the water pump to install my new radiator.. especially since I went thru the whole system with new parts 20k miles ago. But I will be pulling the pump to have a look at the internals for any scoring or grit in the seals. Guessing the same with the thermostat as well. Not much to go wrong with one except fail of old age. But...
I wouldn't worry too much about it. Remove the block drain plug and flush with a hose through every coolant hose with the thermostat out. Run some thermocure in the cooling system for a week to dissolve any rust, reflush, and top off with green coolant and distilled water.

Leave the thermocure in for a week in above freezing weather. Read up on it, its great stuff.
I have been thru a lot of automotive cooling systems and have never seen this much grit. As I mentioned in original post.. when I went thru the system 20k ago I found virtually none of the grit family. Sure a little tiny bit.. hardly noticeable. Hence the reason it raised an alarm bell in my head this time around. I knew it was not catastrophic.. but it had to go. In the end I wanted to know if there was anything else on the table besides rust from the block.

I read up on Thermocure.. so thanks for the heads up @450LX. It has been ordered. Always flushed over and over with just plain water.. plus a lot of those scenarios were with aluminum blocks. However I guess I will now join the High Tech route along with the big boys! Of course there is still the lo-tech distilled water that plays a big part.
Doing a little research and coolant can contain silicate which is sand. Maybe see if your old coolant had silicate in it I guess. The coolant can break down over time and the silicate is left? Maybe try a silicate free coolant next time.
I just finished my first week with thermocure. Today I flushed out some pretty nasty looking bs... almost black in color. My first flush last week produced some sediment of some sort. I didn’t really take too close of a look at it, but quite a bit of it was living in the bottom of my rad.
I'm going with precipitated silicate, like @450LX suggests. Long ago, I saw this in the bottom of a long stored bottle of coolant. If something shifts in the chemistry, the sodium silicate in solution might start to crystallize & drop out as sandy grit - is it white-ish?
The solution is simple - thorough flush & replace properly w new coolant & distilled water.
Did you mix toyota red coolant with green coolant?
Mixing incompatible coolants can cause sedimentation.
Even if you did a distilled water flush after the green coolant, it still seems like the grit shows up when you run the red.

I finally went the Thermocure route as well. Amazing what came out. Amazing how bad it smells too. Like a cat peed on vomit.
Hi, With as many trucks as I keep up I spend a lot of time on maintainance. Gano filters help a lot .Amazing what they pull out. Mike
Thanks for all of the great info. I don't post often with needs.. but when I do.. help is always on the way!

I wracked my brain to remember the scenario of my coolant system overhaul back when I purchased this 80 with 105k miles and just a shade over 5 years ago. When I initially drained the system it did have green coolant. Flushed the block several times and installed a new radiator.. hoses.. water pump.. thermostat.. heater control valve and deleted the rear heater entirely.. including metal lines. However I seem to remember that I somehow spaced flushing the interior heater core. I replaced the heater control valve after I had flushed the system. With no battery and having probably not moved the temp slider.. the valve was more than likely closed.

Assuming this will answer the grit question. So here I am with my great 80 series and I just found out about what happens when you mix coolant. Whether you mean to or not. I am in the process of installing my new.. new.. radiator when I found the grit. There will be NO chance that it will ever happen again.. not with my ownership!

I posted a thread about my new radiator if you are so inclined and have not read it. UPS Delivered Exquisite Fine Art

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