2008 C6. Plan was to drain coolant, replace, run, cool, repeat. First drain is complete, perhaps 7 to 8 qts came out. Topped off coolant tank but did not even take a gallon. Started car and within 2 minutes temp approached 220 with Check Coolant Level (obviously). Let cool, removed cap, there was room in coolant tank to add more. STarted again, took a few mins and then Check Coolant llight again with temp nearing 220.

I thought that all the replacement coolant, almost 2 gallons would "gravity" drain direct to radiator. But apparently it is a repetitive process of running car a few times? Does the car need to run for a certain number of minutes before therm opens and sucks down the coolant? What might I be missing? Thanks.

note: Totally normal thermostat and engine temp behavior before I started this morning.

Update to original post: after the 3rd start/run cycle the coolant level in the surge tank dropped and I was able to add another 1/2 gallon. I will rinse/repeat the start/run cycles until I've replaced what I took about, then let cool completely and see what the surge tank level is.

Update #2: Did two more start/run cycles, topping off coolant surge tank after each one. Now it can run at 200F with no Check Coolant Level light. This was my first DIY attempt at the coolant change (I know it's not a thorough flush) and from reading the posts on this job I wasn't expecting this many iterations to get her topped back off. But I ***think*** I am back on track...

 

Sometimes it can be tough to get all the air out. Here's the procedure from the shop manual.

The key to getting the air out on the first try is performing fill steps 6 - 9 with the cap off.

Good luck, let us know how it works out.

 

Best way to change your coolant is the “vacuum bleed” method…this is the one I use and less than $100.00 from Amazon…a little less than a Starbucks coffee.

 

The shop manual steps, great stuff. Thanks Jim! I was somewhat concerned when the initial fill took 1/2 gallon, and then I was a little fuzzy as to whether to start/run with the pressure cap off, but clearly the SM says to do so. Each start was quickly getting to 220 with Check Coolant Level but I think I am on the right track now as the coolant level has dropped each time, I'ved topped off, and she runs now steady at 200 or so. Rinse repeat, let cool and then final top off. Since my plan was to do this twice (8 clean qts each time) I am now armed with lessons learned and the Shop Manual, thanks again!

 

Thanks, sounds good I will look into this!

 

Yeah, just watch the level in the tank as the motor warms up and add coolant as necessary, keeping the tank mostly full. Once it gets up to temp and the thermostat opens you will notice a drop and see water swirling in the tank. Keep it full and run for a while, then put the cap on, shut it down, check at the next cold start and add coolant as/if necessary. This method will usually get it filled w/o air in one or two tries.

The vacuum pump method is the best/quickest way and is in fact the recommended procedure in the manual, but it is not necessary to get a complete cooling system fill.

That said, for less than 100bux I'm going to get one of those. Easy fill and it will also test for leaks.

 

I think that you did it the best way. About 3 cycles and you are good. If you know that you will need to do 3 cycles and your requirements for the car allow the needed heat and cooling cycles, then it this process is great. Not so great for a shop or owner that needs the car immediately after new coolant.

 

With some other vehicles I've heard people has success by driving up the front end on ramps to help get the air out. Never tried it myself but I suppose it could help.

 

I don’t know why more didn’t come out. I presume you had cap off to help it drain.

Easiest way to fill these cars (I’ve done it this way a couple times now) has been to remove the upper rad hose from the engine and fill from there.
When full, quickly slip it on and fill reservoir.

It’s usually fully burped on the very first run cycle…the most 2. (thanks to fellow forum member Apoclipse for this great tip!)

 

 

See Harbor Freight radiator funnel kit. Carlyle part number 24680, works on just about any thing!