VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 radiator flush procedure for 27

I have been unable to search for the proper flush procedure. Can someone guide me?

I will give you the short description.

Wear splash and eye protection and protective clothing as the acid is hazardous if you don't handle it correctly. And can be hazardous even if you do.

Slowly add pint to quart of muriatic acid to gallon+ of water with constant stirring. Do it outdoors with plenty of ventilation. The object is to have the acid diluted 1:10 to 1:15 ratio with water when in the engine cooling system. Generally most large vehicles will have a 10-15 quart cooling system capacity.

Drain and flush the cooling system in environmentally correct manner at least a couple of times to get as much of the coolant/antifreeze out as possible. Slowly add the dilute acid mixture to the drained radiator (make sure to close the drain valve first). Add water to fill the radiator. Put on radiator cap and start the engine. Turn on the heater to max heat if one is installed. Allow to circulate for 5-10 minutes after the thermostat opens or 10-15 minutes without thermostat. Allow to cool, then run the engine for another heat, cool cycle. Repeat for several cycles. Drain into container for proper disposal while warm but not when hot as it will come after you when you remove the radiator cap.

Rinse several times with water. Removing the lower radiator hose is an effective way to drain but be careful as the water in the block can be hot when the radiator is relatively cool.

Mix a box of baking soda into a gallon of water with stirring. It will take a bit of time to dissolve. Take a small sample and put some of the rinse water in it. Look for bubbles. If none then add the baking soda solution to the radiator and circulate until hot. Drain and flush with water. Now you can add the distilled water and concentrated coolant or 50/50 coolant.

Thanks very much for the info. Sounds a little scary and your cautions are appreciated.

As long as you have an healthy respect for the chemical hazards it is a relatively safe procedure. The main thing to remember is to only add the acid to water. NEVER add water to acid! And always use eye protection. The acid in your stomach is stronger than what you are cleaning your radiator with.

While the above works well, What I use is several fills and drain outs of nothing but pure distilled water or rain water. I fill with rain water and run engine till hot, let set for a cople days get hot again and drain out. Refill and do the same thing till the water comes out crystal clear. If it takes a week and several drain outs, then so be it but it will clean out very nicely! No harsh chemicals needed. However it really only works for lime build up. Won't do much for rust. You should see how nice rain water cleanes out the heater and pipes in a hot tub!