Draining coolant in 2015 Mustang GT with PP

[gqneon]

So I was diligently going about getting my car ready for my power adder install next week and went to drain the coolant. I put it on stands, got under it and got the lower engine cover off, put a 3/8" hose on the petcock drain area and opened the petcock. I also had removed the overflow tank cap. All per the shop manual and common sense. It would only drain about a gallon. So I took it off the ramps, same thing. I thought maybe the angle was the issue. So I refilled it and warmed it up to operating temp, thinking maybe it had something to do with the thermostat being shut still. Then did it again. Same thing, just about a gallon.

The PP edition holds right at 3.5 gallons, with about 80% able to removed with the vehicle engine installed in the car. That's about 2.8 gallons, so roughly a third of the available coolant that should be draining. The car's level, the heater is set to max (engine obviously not running), and I've even completely removed the petcock screw thinking... well... lots of things.

Somethings up - what am I missing? I should have a big old pan full of the coolant under my car, and I don't want to pop my thermostat housing off to put in the 170 thermostat before the system is drained properly so it doesn't spew out all over my belts and components.

Fill in the blank if you know what I'm not doing here, please. Car's apart and would love to be done!

 

[Anthony K]

Gallon is probably close enough to change the stat without a big mess

 

[908ssp]

I changed the thermostat a couple days ago without draining any water out. I don't think I lost more than a couple cups. Once done I took hose a rinsed off the under tray.

 

[gqneon]

Thanks, I went ahead and changed it with no issues with my missing 1.3 gallons. Hoses were clear of coolant and so was the tank, so I swapped to the Procharger coolant tank while I was at it. It's such easy work once you get used to it, its just been forever since I've gotten to tinker with cars.

 

[gqneon]

Update - thermostat and about 30% coolant to distilled water with about 6 ounces of Purple Ice (water wetter type product that doesn't do all the nasty things water wetter can do after reading up on it) and I can say that cruising around and all, the head temp didn't get over 195, whereas before it was 200-205 minimum and up to 216 or so.

Funny thing is, trapped air can be tricky. I was pulling down the alley to park it at the house and stopped for a second, and watched temp climb fairly rapidly on cylinder head temp to 205. I'm thinking I found an air pocket, so I pulled in a couple seconds later and cut the engine. Popped overflow cap and levels are fine. I might have to drain it in the a.m. and hit it with the coolant vaccum refill tool but would probably get the cops called if I fired up the compressor tonight otherwise I'd be out there trying it now.

Maybe I can park it uphill or on ramps to "burp" it a little better since I have a slight grade to my driveway.

 

[SID297]

If you want to spend a little money this tool is invaluable for purging a cooling system:

http://www.amazon.com/UView-550000-...e=UTF8&qid=1434384901&sr=8-2&keywords=rad+vac


I'm blown away by how many times I've used mine.

 

[gqneon]

Got one sitting in my garage but didn't think I could use it since my system only wanted to let out about 1/3rd of the coolant for some reason. System seems to be just fine now, heater, a/c, and it stays in the mid 170-180 coolant temp and about 180-195 head temp depending. It will still get almost as hot (about 5 defrees cooler at max) if I just let it sit and heat soak but it drops temp faster and keeps it lower from the reduced coolant ratio and purple ice. When it's moving its a solid 10-15 degrees cooler. Anything I can get to reduce detonation under boost, I'm good with.