The mother of all Coolant System Flushes...
 

When I installed a new motor a couple of years ago, I noticed that the coolant looked as if there were fish scales floating around in it. I assume this is what coolant system people refer to as "scale" but I could be wrong. Either way, it didn't look kosher so I did a full drain and refilled but it looked the same.

Fast forward to this year. I was helping moconnor on his Vmount and we noticed his coolant looked kinda dirty. He did a coolant system flush using something like this:
http://www.prestone.com/node/424
and flushed with pure water for a cooling cycle and that seemed to clear it up. His car only has 50k miles or so. Mine has 150k.

Given his results, I decided to flush my coolant system. Figured I'd get the Prestone Super Cleaner since my coolant looked dirty and then I'd do one fill/flush with distilled water and I'd be good to go. Yeah right.... Didn't quite work out that way....


I started out by buying a bottle of the Prestone Super Cleaner since it's description is "This formula removes heavy rust and scale deposits.":
http://www.prestone.com/node/379

I fully drained the system by removing the small 14mm bolt on the driver side of the block and removing the radiator to fully drain it. Then I filled it with 2 gallons of distilled water and the Prestone Super Cleaner and drove the car to/from work for a week so that I could get the required 3-6 hours of run time allowing the stuff to do its job. Then I fully drained the system again and refilled with another ~2 gallons of distilled water and ran the car through another heat cycle*.

*By heat cycle I mean bring the car up to temps allowing the thermostat to open so that the water circulates. I set the heater to high and set it to defrost to ensure that the heater core gets a full flush as well. Sometimes I'd drive it. Other times I'd just let it run until it warmed up to over 85* C.

I was now ready to drain the pure distilled water which I expected to be nice and clean. I was very surprised at how dirty the water looked. It was kinda brownish and nasty looking. So I decided to do it again. Same result.

How many more times did you think I had to do this until the water started coming out clean looking?
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Long story short, I went through 14 gallons of distilled water flushing the system out. 7 flush cycles using distilled water. Only after the 7th cycle did the water being drained finally start looking clean enough that I was comfortable calling my flush 98% successful.

My car is a 93 with 150k miles. I'm pretty sure the coolant system was never flushed in its life. At some point, it had been run on Evans coolant. I don't think it ever had any sealer or anything like that added to the system.

If you are as meticulous as I am about maintenance and a clean running, well performing car, you guys might want to consider doing a couple of flushes at some point.

Ew. Sounds like something to do if you've bought a car with unclear maintenance history.

David

That is impressive

After the final flush, I filled with a little over a gallon of distilled water, some prestone green anti freeze and a bottle of Redline Water Wetter.

After running the car with the Lisle funnel to get the air bubbles out, I tested the coolant system using a Coolant System Pressure Tester. I found a leak on one of the silicon hoses to my custom radiator setup (V-mount by Speed of light). I hadn't tightened one of the clamps sufficiently. tightened it up and it went away.

Here is a pic of the coolant system tester testing on my Spec Miata. Same thing on the FD except attach the big chrome thing to the filler neck at the thermostat housing.

https://lh3.googleusercontent.com/-1...0/DSC01499.JPG

Let it sit for a while to ensure pressure holds over time.

https://lh4.googleusercontent.com/-c...0/DSC01501.JPG

Great job :icon_tup:

How can I flush my engines coolant passages, when motor out of the car ?
Can I use the same stuff ? Does it need to be heated ? I could mix it with hot water :nod:

Steven

iv been thinking about doing my coolant change recently also. Might just have to do exactly what you did, if i find time... where again is the coolant drain on the block?

Did you change coolant often?

The reason I ask is that one of the things on the "spring maintenance" when I'm getting the car out of storage every year is changing coolant. But I don't flush, I just change with distilled water. I've never used that flush, but then I've never had the swamp water coolant like you've described. :confused:

Wow 14 gallons! Gotta make sure...

some could be more, or less depending on how dirty the system is

FWIW- Mercedes has been using G-05 coolant for over two decades, as well as I, and I've NEVER had scale build-up. My Master ASE mechanic also has noted the same. IMHO, G-05 is a far superior coolant than the "old green stuff", I'd run it at your next flush in 18-months.

:-) neil

I am planning to run Evans coolant once the engine is back together.
Might be a good Idea to hook the hose on the upper waterpump tube and turn up the water to flush the block. The engine is out of the car so I can clean it a bit, or fill it with said cleaner.

Btw the block drain plug is on the drivers side engine mount. Thats around under the plugs.
When looking frum under the engine it is over the mount, so you have to reach on top of the mount to open it.

Edit: ...;)

Way to read into it Josh. ;)
I said a flush was never done. Coolant got changed once a year while in my possession - last 30k miles.

Neil,

The only time I noticed "scale" was after the new motor. Not sure if it came from the assembly lube on the new motor or what but it was there. 17 years of use and varied coolant system changes w/o a flush was definitely due for some attention.

What's so special about G-05?

What really comes to mind after reading through this is, why is it that so many people neglect their coolant and sometimes other fluids? The cooling system is one of the more critical parts of keeping our cars running healthy, and the coolant is a critical component of that system. Most people I know change their oil well ahead of the recommended 3k or 3 months. Yet when it comes to some of the other fluids in our cars the seem to just be neglected.

Just to clarify I'm speaking in general, not accusing the OP of doing something bad.

Great point.
I suspect at least one reason that coolant gets neglected by some is because it can be. Unless taken to the extreme there's usually not alot of consequence for the average modern piston engine. But they don't have coolant seals.

Please forgive the nit-picking here, but nothing happens to heater coolant flow on either an FD or an Nx* Miata by moving the heater controls. Full coolant flow through the heater core exists at all settings, and only air diversion controls heat delivered from the HVAC system.

*(x=A,B, or C)

Thanks for picking that nit. I learned something as a result. :)

Great post. I just got my FD and am certainly going to flush it as soon as spring comes. Forgive me but I have a couple n00b questions...

1) You said "I fully drained the system by removing the small 14mm bolt on the driver side of the block and removing the radiator to fully drain it"... did you remove the entire radiator? Or just another bolt? If it was just another bolt, where is it located?

2) To put the distilled water in, you just pour it into the radiator cap?

3) During your flushs, you mention you drove it for a week or so with just distilled water in it... just to confirm, that is ok to do? (drive around with no antifreeze in your car... just distilled water)

4) From the searching and reading I have done, people always specifically mention GREEN anti-freeze. Does it matter if it is green or yellow? The people at my local auto parts store say they are interchangable.

Thanks
Jeff

How many hours of run time did it take to flush moconnor's FD?

+1

Also:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/faq-3rd-gen-other-useful-links-68640/
Scroll down to the C section

Thanks for the links guys.. exactly what I was looking for.

The only question I was unable to find was the green vs yellow antifreeze question. One link said either was fine. Can someone confirm?

IIRC the green and yellow are the same stuff, just different manufacturers.

You can also use CLR for things like the heater core, just make sure to flush it out.

Yellow and green may share the same "base" Ethylene Glycol", but their chemistries Inorganic, Organic, and Hybrid Organic acid technolgoy (IAT, OAT, HOAT); some are phosphate-free; some are low-silicate); and additives (e.g., benzoate) are different.

Even among "green" and "yellow" there are differences.

If you don't know what's in there, flush it out completely, rinse, and then fill and document for the future.

If you have to mix and are unsure, mix within the same color, and try not to exceed 10% of the total volume of your coolan system (e.g., 2-liters capacity, replace no more than 200ml).

Check out this chart:
http://www.eetcorp.com/antifreeze/Coolants_matrix.pdf

:-) neil