My heater has been weak lately so I decided to do a coolant flush with hopes that would resolve the problem. I am using one of those coolant radiator funnels for burping air. So I drained the system and then refilled it with the engine not running until there was a small amount of coolant visible in the funnel, at this point in the process I started the engine to begin the burping process. When the engine temp got around 200 the funnel started to fill rapidly with coolant and before I knew it there was a big geyser shooting out the radiator. Anyone know where I should start first? Thank you.

 

Fill the radiator back up, put the cap on, and turn on the engine. Watch the temp until it gets to 200-ish so you know the t-stat has opened and the water pump is moving water through the whole system. let it go for a few minutes.. Then let the temp drop so you can take the cap back off safely and put more liquid in, whether its water, flush, or antifreeze, or whatever it is your putting in.

The geyser is because the water got hot enough to boil (in the engine) and it came shooting out when the t-stat opened. so if the cap is on, it cant shoot out.

 

I am using water for the flushes. I've just never seen that happen before.

 

Water will work unless the system is filthy and needs chemicals to help get it all out.
but to avoid the geyser the cap has to be on when the engine is running to get hot so the t stat will open and then the whole system can get flushed. Then when it's cooled off, open the cap and add more water if it dropped down. Continue flushing if desired or needed. Then openload drain plug so all that can come out and I usually put the water hose in the radiator help get stuff out of there. Fill the system back up and flush it out with water one more time. then you basically do the same thing when filling it up with water and antifreeze. Fill it up until it's full and then put the cap on and turn the engine on and let it go till it gets to operating temp let It go for a minute and then turn the engine off, let it cool so there's not another geyser and then add the rest of your antifreeze or water till it's full again. ThatpThat doesn't make much sense (but it did in my head when I was thinking about it hahaha) but I bet there's a step-by-step instruction somewhere on the internet....

 

an easy way I have found to avoid air pockets is fill cooling system with nose up, leave rad cap off overnight, air bubbles mainly seem to make their own way out