Jul 12, 2018
Richmond, BC
2005 C6 Z51 6 spd
It's been 5 years so time to flush the coolant. I flushed it myself last time, so opted to do it again. It's a little tricky as you can get air stuck in the system, but with the right procedure you can bleed the air from the steam port and don't need an air bleeding system.

I used AC Delco Dexcool since that's what I used last time and I had half a container left. The cooling system capacity is 11.9 L/3.15 gal, you will need 2 containers of concentrate (7.65L/2 gal) for 5.96L/1.56 gal of coolant and water for a 50/50 mix. Metro Vancouver water is soft with very little minerals so I opted for tap water for both flushing but you may want to use distilled water if you have hard water.

I put the car up on ramps and drained the radiator from the drain valve on the right hand side.

I drained all the coolant, filled with water, ran the engine with the heat on until the thermostat opened, drained, and repeated until the water ran mostly clear. This was the second last drain and you can see the water clearing up, but there are still lots of solids. All that solid stuff made me glad that I was flushing it on time.

I removed the surge tank and cleaned it as best I could, but it's chambered so hard to get into, so I just mixed some detergent in it and gave it a good shake and rinse. Once the cooling system drained and flushed, the cooling system contained some water, so I mixed the coolant and water in the system. You can bleed the air in the system from the steam port by blowing air into the hose until coolants runs out the steam port. I filled the surge tank with coolant, installed the cap, disconnected the hose from the steam port on the throttle body (circled below) and blew air into the hose which draws the coolant from the tank into the rest of the system and purges air from the steam port.

After pouring in the coolant, I ran the engine with the heater on until the thermostat opened and the rest of the air escaped. I backed the car off the ramps to get it level, topped up with water and ran the engine to confirm proper cooling. Based on last time I expect to have to add a little more water over the next couple heat cycles but it should be fine to drive.

Update: here is the coolant level after the first cool down. It's not too low but definitely needs topping up.


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