Iron Grit in Radiator

[Big Jake]

My 1967 Charger big block has a very unique problem. Appoximately 10k after rebuild there is iron grit in the radiator. When I insert a small telescoping magnet into the top of the radiator it comes out with small amount of iron grit that resembles coffee grounds. I flushed the radiator the best I could and refilled with anifreeze. However the problem continues. Any ideas where it's coming from and is it fatal?

 

[Photon440]

About the only moving part in the cooling system internals is the water pump, is it possible that something is 'self machining' in there?

 

[R413]

Remove the screw-in plugs from the sides of the block and rinse it out. Remove lower rad hose and flush that also.

sometimes this stuff comes loose from the block cleaning and takes some effort to get it all out.

 

[diesel_lv]

As @R413 said, I've got it in my '67 block when i drain my coolant. I've drained n flushed at least 8 times w distilled water and still get it. They do make an inline filter for cooling systems. I've just never done it.
engine cooling system filter - Google Search

 

[Bill M]

changing freeze plugs on a 340 that has been in storage for 15-18 years and not running, been washing out a PILE of sludge. I can fill a cup there is so much. The lower plugs were rusted out. Appearances was i was not the first one to do this to this engine.
Looks like mud and stones when flushing it. Even after all that flushing i can still feel grit inside the engine with my fingers.
First time in 40 years i have ever needed to do freeze plugs. Was a Florida car, maybe they don't use antifreeze??

 

[69a100]

Appoximately 10k after rebuild there is iron grit in the radiator. I flushed the radiator the best I could and refilled with anifreeze. However the problem continues. Any ideas where it's coming from and is it fatal?

How well was the internal part of the block washed & flushed before the rebuild? Do you know?

 

[diesel_lv]

Most of our cars in the 60's, 70's n 80's topped off the cooling system w garden hose or hose at gas station. Neither is or was distilll. Would just keep topping off n not putting in antifreeze. It's not until the cars became an investment or heirloom that most of us actually started paying attention to the ratios n corrosion prohibitors.

 

[Big Jake]

How well was the internal part of the block washed & flushed before the rebuild? Do you know?

I'm not sure. The engine was rebuilt before I bought the car.
Why is there rust in there when antifreeze is suppose to prevent it?
I'm surprised the themosat still seals with all the grit. You'd think it would prevent it from fully closing when cold.
However the temp gauge readings are fine.

 

[Big Bad Dad]

If the engine was bored oversize and honed, if the mains were align bored, or if the block was decked, there are probably cast iron shavings from the machine operations in the water jackets. I used to work in a machine shop, and it was critical to completely clean and flush out a block if we were assembling the engine. If the customers just had the machining done and were then going to build their own engine, the final cleaning was on them. And we occasionally had a comeback complaint that could be traced back to them not doing the final clean and flush before assembly. That is a possibility for the iron grit you are finding.

 

[1 Wild R/T]

I just got done popping freeze plugs and flushing a 340... You can try flushing through the block drains but the holes are pretty small... I knock out the most accessible plug on each side, the two down low on the front of the block & I remove the thermostat plug all the hoses... Then I use the garden hose cranked wide open, you want as much volume as possible... If you watch the water flow out the plug holes you probably won't see much but if you stick your hand down along the side of the engine into the flow you'll sure feel all sorts of hard debris being flushed out... I bounce back & forth from the thermostat hole to the front freeze plug holes until the water comes out clean.. Overkill? Maybe, but it's not hard to do, I've done it on practically every car I've owned & I know I've done the best I can short of taking the engine out of the car & having the block boiled...

 

[diesel_lv]

I'm not sure. The engine was rebuilt before I bought the car.
Why is there rust in there when antifreeze is suppose to prevent it?
I'm surprised the themosat still seals with all the grit. You'd think it would prevent it from fully closing when cold.
However the temp gauge readings are fine.

Mine was tanked and bottom assembled by shop, still have iron dust in mine. Cools just fine in 125° summers pulling jet boat, but very unnerving the 1st time I flushed it. I'm assuming either they didn't run brushes through every water jacket when doing final cleaning after dipping n machining, or there was just so much rust built up after yrs of pump jockeys just topping off w the gas station hose.