How to remove silicate and scale from cooling system?

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I'm working on a nc700 that has had wrong (green, silicated) coolant in there for most of its life. The cooling system internals are now coated with a white powdery substance similar to chalk. At its worst, white flakes were visible circulating in the radiator, I got those out after a few flushes. I can remove the white scale with a scotchbrite or a metal brush, but obviously brushes can't reach into the engine's internal passageways, so I am looking for a chemical solution here.

How do I get rid of this coating?

Steps already taken:
-Multiple commercial radiator flushes
-Multiple distilled water flushes
-Cooling system disassembled and inspected
-One test piece has been targeted for trying different cleaning methods - overnight vinegar soaking made no difference, and I'm now trying a CLR soak with results TBC.
 

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ST13Fred

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finditparts.com has a Baldwin CSC5012 1 US gallon coolant system cleaner. Have no personal knowledge but a possible start. Stick with Honda brand coolant.
3 years (no mileage interval) is the regular coolant replacement recommendation for the NC. Good luck.
 
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4 hours of soaking in hot 50/50 CLR and water was ineffective. I changed tactic and went for a strong base - caustic soda, aka sodium hydroxide, mixed as per the packaging recommendation (about 75g pellets in 1.5L water). This has been effective on my test part, it fizzes and bubbles the moment you lower it into solution. About an hour of soaking has removed the bulk of the white deposits.

So the plan is to reassemble the cooling system with the old seals, sans thermostat, and (briefly) flush it out with this strong alkaline mix, then distilled water, then reassemble with all the new rubbers and seals.

This has been loads of work - RTFM - use the right coolant!
 

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itsmenc700

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Wrong coolant???
OK its not "Honda" coolant but it was coolant.
The only difference between ALL the coolants out there is what they use to protect the engine from rusting and plugging up.
The green that you called wrong is only because the Honda ISN'T green. It still has properties to protect an engine.
I'll get blasted for this but you can use ANY coolant in any engine no matter the color!
Some recommend change intervals shorter than others, but they are still good to use.
 

670cc

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Wrong coolant???
OK its not "Honda" coolant but it was coolant.
The only difference between ALL the coolants out there is what they use to protect the engine from rusting and plugging up.
The green that you called wrong is only because the Honda ISN'T green. It still has properties to protect an engine.
I'll get blasted for this but you can use ANY coolant in any engine no matter the color!
Some recommend change intervals shorter than others, but they are still good to use.
I’m not going to blast you, but I am going to say there is a whole lot of science in coolant chemistry that some people may not be aware of. Put whatever you want in your bike.

Honda‘s coolant recommendation primarily revolves around avoiding the silicates additive. The silicates are abrasive and have been known to damage the water pump. And now we have the newer, often incompatible formulas like Dexcool, HOAT, OAT. There are purple, orange, green, etc identifiers for a reason . Anyone that thinks these are all the same and compatible might want to do more research. I don’t know it all but I know there is a lot to learn about coolants. I keep three different coolant types on hand for various vehicles.
 
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I know vinegar removes scale from bathroom fixtures...I wonder if pouring a gallon of vinegar into the system and allow it to circulate will do the trick...I wouldnt want to circulate Lye (sodium hydroxide) thru the system...may be too caustic....
Agreed, it's pretty aggressive stuff. I'm only doing it because I've got all new rubber parts on hand. The only issue on my mind is the water pump impeller seal - not a serviceable part. What seals the shaft in the attached picture? Isn't it a ceramic seal?

The pictured part in my original post has soaked for two hours and it hasn't removed enough aluminium to upset any mechanical fits and tolerances - all the factory paint, surface etching, and batch numbers are still crisp and clear. So hopefully running the same concentration of solution through the cooling system for ~20 minutes will descale the internal water galleys but not destroy the ceramic water pump seal.
 

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Klap

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Wrong coolant???
OK its not "Honda" coolant but it was coolant.
The only difference between ALL the coolants out there is what they use to protect the engine from rusting and plugging up.
The green that you called wrong is only because the Honda ISN'T green. It still has properties to protect an engine.
I'll get blasted for this but you can use ANY coolant in any engine no matter the color!
Some recommend change intervals shorter than others, but they are still good to use.
Not true. Silicated coolants are NOT Recommended for most Honda motorcycle engines. They have been known to cause failures on water pump seals, bearings, etc. Best to stick with Honda Type 2.
 

itsmenc700

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I know not to mix the different colors because of different additives.
But engines have had the same type metals for years.
The whole point of the additives is to stop the metals inside the engine from destroying themselves.
These engines dont have some new metal that requires a specific coolant.
Seals - maybe but it would take many years and/or miles for anything to show up as damage.

Posted above -"Not true. Silicated coolants are NOT Recommended for most Honda motorcycle engines."

Yet it would be OK to put vinegar in the engine. That stuff wont harm anything - right?!?!?
 

670cc

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I know not to mix the different colors because of different additives.
But engines have had the same type metals for years.
The whole point of the additives is to stop the metals inside the engine from destroying themselves.
These engines dont have some new metal that requires a specific coolant.
Seals - maybe but it would take many years and/or miles for anything to show up as damage.

Posted above -"Not true. Silicated coolants are NOT Recommended for most Honda motorcycle engines."

Yet it would be OK to put vinegar in the engine. That stuff wont harm anything - right?!?!?
Just do an internet search for terms "honda motorcycle water pump failures silicates". I won't bother posting the links because they're easy to find. Put in plain old green silicate automotive coolant in your NC and you might add your Honda to the failed pump list.
 

itsmenc700

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My point was the use of vinegar!!
Also the use of silicates has almost been eliminated.
So other than a few other additives a blue Kia coolant, or a Pink Toyota coolant will work, as long as its silicate free.
The problem is there are silicate free coolant that are still colored green!
 
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670cc

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Posted above -"Not true. Silicated coolants are NOT Recommended for most Honda motorcycle engines."

Yet it would be OK to put vinegar in the engine. That stuff wont harm anything - right?!?!?
That’s sort of a “whataboutism“ comment, don’t you think? First you stated that any coolant could be used in any engine, but when that was disputed, now you’re wanting to direct the focus instead to the affects of vinegar used a cleaning agent.

The vinegar is being used as a one time flushing agent to rid the system of contamination potentially caused by past use of the wrong coolant. I thought it was pretty clear that the vinegar itself will not be used as a coolant. The owner is prepared to replace or rebuild any parts that the vinegar or similar cleaning agents might harm.
 

MZ5

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There are silicate free coolant that are still colored green!

That is correct. Plain green Prestone is silicate-free and meets the only requirement(s) stated for coolant by Honda.

OP, I hope you can get the deposits cleaned up without damaging the water pump or its bearing.
 
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Janus

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Just do an internet search for terms "honda motorcycle water pump failures silicates". I won't bother posting the links because they're easy to find. Put in plain old green silicate automotive coolant in your NC and you might add your Honda to the failed pump list.
Just to add confusion to this thread (perhaps my own)... I think my OEM fluid was green. Now Honda Pro fluid is blue. I seem to recall a post or manufacturer statement saying it was okay to mix them too.
 

670cc

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Just to add confusion to this thread (perhaps my own)... I think my OEM fluid was green. Now Honda Pro fluid is blue. I seem to recall a post or manufacturer statement saying it was okay to mix them too.
In the Honda world, I thing the coolant designation "Type 2" is the key for compatibilty and suitability for the NC. I think the Pro Honda HP coolant says Type 2 on the bottle's rear label.
 
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I took the plunge and flushed the system with caustic soda. First I did 2x 15 minute flushes with caustic soda, then flushed with vinegar to neutralise the alkaline, and then I ran multiple distilled water flushes through the system, before disassembling everything and rinsing individual parts and reverse flushing the block.

The areas of high pressure around the water pump output cleaned up quickly. Loads of what I assume to be crystalline silica came out in the flushes. Flakes/crystals got stuck in awkward flow corners, where fluid takes 90 degree bends and in low pressure areas like the water pump inlet. The caustic soda also stripped off a lot of paint on the inside of radiator hose barbs and under the cap. The inside of the water pump cover (test part) now has a soft, dull surface finish that dirties a cloth if you wipe it across the surface. I'm glad I stopped the soda flush when I did, because the soda definitely eats aluminium. The water pump seal seems fine, although there is some surface rust developing on the impeller already, probably due to the soda stripping off the galvanic coating of the stamped steel impeller.

I've attached some before and after photos, this treatment definitely worked to strip the silica out of the system. But I would not recommend doing this job as any kind of routine maintenance - I simply had no other option to recover my cooling system from having the wrong coolant filled in it. I will be reinstalling all the new parts tomorrow and hopefully the cooling system will function like new again.
 

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MZ5

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Glad it's doing what you wanted.

FWIW, I kinda doubt you're looking at coolant-based silicate drop-out problems here. I think you're more likely looking at the results, primarily, of using hard tap water in the cooling system. Those hard scale deposits are what one generally associates with calcium and magnesium from the water. Silicates can certainly be a component of the deposits, perhaps a significant component, but those silicates generally or at least frequently come from the water, too.

Again, I'm glad you're getting it cleaned up like you want. If your water pump is rusting at this point, I'd consider replacement if it was mine.
 

showkey

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Agree ^^^^^^^^^^^^^

The water quality is far more likely to be the root cause of the OP a problem.
or a water quality plus coolant compatibility issue.
One argument for quality branded premixed coolant is the water part is a known quality.

some vehicle manufacturers have no problem with silicates ...The silicate also coats the metallic parts of your machine inhibiting corrosion within the system.................Honda’s issue with silicates has always been the water pump seal damage and that goes back 50 years and applies to bike and cars.

Also.......... agree the coolant color and chemistry has been muddied over the last 20 years and you must read the labels very carefully.
 
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BFair

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I agree with MZ5. Those deposits are identical with the scale I get from flushing my hot water heater. I've never seen that kind of scale from any type of antifreeze.

My guess someone ran hard tap water for a bit before changing. Once heated the crystals come out of the tap water, check your tea kettle and shower head. Aluminum corrosion is indicative of the system not having a corrosion inhibitive package from brand coolant.

Looks like you did a great job with the flushing and taking pictures. Add a good coolant and go on with you life, ride. Any damage will show up in weaping seals down the rode. How far ?????
 
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