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)
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
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
Bucket or catch-basin
Water (Makeup water should be soft water or distilled water)
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
3/ Remove and clean the overflow tank. It pulls straight up off of its mounting
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."