# Flushing engine coolant



## TSOJOURNER (Dec 16, 1999)

Anyone have any good advice on how to perform a really good engine flush for the freshwater side? 

I was noticing my coolant looks pretty nasty. Last time I did a drain & fill but I want to really get everything good get all the scale and gunk out. 
Maybe use the Prestone radiator flush product? I have a hydronic heater so I can easily use the hoses for that to perform the flush. Bought a drill pump to get the old coolant out & bought some fleet service antifreeze that is supposed to be better for diesels. Now I am just waiting for the new thermostat to come.


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## jason3317 (Dec 20, 2007)

*Drain and fill*

I followed the drain and fill method a couple of weeks ago. I drained, refilled with the Prestone flush/cleaner + water - then drained, filled with water (did this twice) and finally finished by adding a pre-mixed 50/50 antifreeze with anti-corrorsion additives. Each drain / fill cycle, I allowed the engine to reach operating temperature and cool before draining.

I probably wasn't able to get 100% new coolant exchanged, but am satisfied with the results for now.

The initial drain plus flush was pretty nasty looking.

JS


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## Trekka (Jul 16, 2006)

The Prestone is pretty mild. The active ingredient is sodium citrate which is also a food additive. Years ago we could get some serious cleaners, but I have not been able to find any in the present era. Zerex makes a flush that's a little stronger, but still very mild.


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## Brezzin (Dec 4, 2006)

Once you've changed the coolant, how do you depose of it?


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## T37Chef (Oct 9, 2006)

You may want to try some of these products from Trac Ecological. It looks like the "Trac Descaler" is what you want. I have used the "Barnacle Buster" to clean my raw water system and it worked very well. As easy as winterizing; TRAC Ecological Marine Products










Purchase the concentrates, less shipping charges


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## TSOJOURNER (Dec 16, 1999)

Brezzin said:


> Once you've changed the coolant, how do you depose of it?


The drain. NOT THE STORM DRAIN. And not if you have a septic system. Check with your waste water plant first. Everyplace I have lived (and yes I have checked) has recommended disposal in the sanitary sewer. Some marinas also have an oily water pumpout station that might work.


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## Trekka (Jul 16, 2006)

Brezzin said:


> Once you've changed the coolant, how do you depose of it?


At my boatyard there are separate collection containers for oil and antifreeze. I put mine in the appropriate tank.


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## Warren M. (Jun 3, 2006)

MACS 2001: GM and Texaco "Bare All" about DEX-COOL®

The below advice, from Mack Boring, is for the Yanmar 3GM30F, but is essentially the same procedure for most engines:

"Coolant Change - Yanmar 3GM30FC (Japan, circa 1999)Coolant Change - Yanmar 
3GM30FC (Japan, circa 1999)

Background: 
Yanmar accepts the following antifreeze applications in their products, present 
and past models: 
1. Ethylene glycol-Changed annually regardless of hours of operation. 
2. Extended Life Antifreeze or Coolant (Meets or exceeds ASTM D3306 & D4985) 
Changed every two years or 250 hours whichever comes first. 
-Yanmar Ultralife YG30 
-Dex-Cool Long Lfe Coolant 
-Havoline Extended Life Antifreeze 
Benefits of extended life coolants: 
1. reduces hard scale build up 
2. better heat transfer 
3. no phosphate or silicate formation 
4. long term corrosion protection for aluminum, bronze and cast iron 
5. improved water pump life

Thomas J. Watts 
Technical Support, Mack Boring & Parts Company 
908-964-0700 ext. 286 
[email protected]

Equipment List: 
0.5 gal Dexcool-type Extended Life Antifreeze (ex. Prestone 5yr/150000mi) 
Or 1 gal of pre-mix version of above 
Coolant system flush (must be safe for aluminum) (ex. Prestone Super 
Flush)-Optional 
Pliers 
Funnel 
Bucket or catch-basin 
Water (Makeup water should be soft water or distilled water)

Instructions: 
1/ On a cool engine, loosen the filler cap and drain old coolant into container. 
On my engine, there are 3 drain points. Most volume came out of the block drain 
fitting on the port side just aft of the oil filter. Approx. 16 oz came out of 
the 2 drains on the heat exchanger, starboard side.

2/ After draining the engine, remove one of the hot water tank hoses from the 
top front of the engine. Keep the 2 coolant drains on the engine open. Put on 
the radiator cap and put your finger over the opening on the engine where the 
hot water heater hose was connected. Clean off the hot water heater hose and 
then blow on the hose and the hot water heater loop is emptied (about 1/2 
gallon).

3/ Remove and clean the overflow tank. It pulls straight up off of its mounting 
bracket.

4/ Close all drains and fill with water. Replace filler cap. Run engine until 
thermostat opens and temperature stabilizes. Then shutdown and allow to cool.

5/ Drain (ie. Repeat step 1) Refill with coolant system flush chemical 
(optional) plus water as required to fill. Run engine until thermostat opens. 
Shutdown and allow to cool.

7/ Drain (ie. Repeat step 1) Refill with water to flush out the cleaning 
chemical (ie. Repeat step 3). Do this 3 or 4 times until drained water is clean 
and free from ethylene glycol (green) antifreeze. 
Note: if you are staying with the EG antifreeze or did not use the flush 
chemical, 1 or 2 water flushes should be sufficient.

8/ Drain for the last time. Refill with the 50/50 mix of Dexcool-type extended 
life antifreeze. Fill overflow tank slightly above the "min" mark.

9/ Start engine, check for leaks and proper temperature. After shutdown, recheck 
level in overflow tank."


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## Melrna (Apr 6, 2004)

When I had my Yanmar coolant changed, after the Yanmar mechanic put new coolant in the engine he also bleed the air out of the hot water heater. Said most sailors forget to do this. Said can create an air block.


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## TSOJOURNER (Dec 16, 1999)

Melrna said:


> When I had my Yanmar coolant changed, after the Yanmar mechanic put new coolant in the engine he also bleed the air out of the hot water heater. Said most sailors forget to do this. Said can create an air block.


2 gallons out. 1 gallon in? Oops!


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## Cptken (Apr 23, 2008)

*Hot Water Heater loop*

In almost all installations the hot water heater will not self prime. And most situations will cause an overheat condition. In step 2 it was drained. I find it easiest to remove both ends of the loop from the engine. Blow in one end with the other hose over a bucket to drain. To fill pour in one hose until it comes out the other, reattach.


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