Why can't I drain my coolant?

[Squid Gloves]

07 Speed3 with 182K miles. I'm trying to flush and replace the coolant since I just replaced the stock oil cooler and I have no way of knowing what coolant the previous owner used, but I can't get the coolant to drain properly. With every car I've owned before, I've been able to drain all the coolant via the radiator, cycle a few gallons of distilled water through everything, repeat a couple times and refill the coolant, so I assumed it would be the same process on this car.

I tried draining the coolant from the radiator first with the reservoir cap off, but hardly anything actually came out. Even when I disconnected one of the oil cooler hoses, only about a gallon came out. I added water back into the reservoir and did the bleed procedure and went to drain it, and this time it trickled out a little less than a gallon after about 15 minutes. After the third time doing this, nothing came out of the radiator. So now I'm running probably 80:20 water:coolant, and I can't get it to all dump out so I can run 50:50. What am I doing wrong here?

The car is also driving fine and won't go above halfway on the temp gauge. I drove aggressively around my area for about 5 miles and I couldn't get it to overheat or behave weirdly. I'm in socal so I'm not concerned with freezing temperatures, but I'm still concerned about the fact that I can't fully drain it.

 

[Enki]

The whole thing only holds like 2 gallons, and you also need to factor in the heater core, which can hold a good portion of that. Maybe jack the back of the car up in the air (chock the fronts and put it in first though before you do this) and that might help drain the rest. Also, if you go key on (no start) and then turn the heater on, that *might* do something but I'm not sure.

 

[Awafrican]

yes sounds about right. this is the reason I took to doing two drain and fills with 50/50 premix because it's hard to get it all out.
drain it, fill, drive for a bit, then repeat until I've put in about 3 jugs. served me well for 13 years of my speed.

I know others around here ended up doing the same to avoid worrying about ratios.

 

[Squid Gloves]

The whole thing only holds like 2 gallons, and you also need to factor in the heater core, which can hold a good portion of that. Maybe jack the back of the car up in the air (chock the fronts and put it in first though before you do this) and that might help drain the rest. Also, if you go key on (no start) and then turn the heater on, that *might* do something but I'm not sure.

Ah okay, I knew it took two gallons but I didn't realize it could still hold THAT much coolant. I had the passenger side jacked up but I'll try it from the rear instead

 

[Enki]

Ah that could be a problem as well. Every time I've drained mine, it's been flat or on jack stands; jacking up the passenger side results in raising the coolant inlet point above the coolant level inside the block.

 

[Squid Gloves]

yes sounds about right. this is the reason I took to doing two drain and fills with 50/50 premix because it's hard to get it all out.
drain it, fill, drive for a bit, then repeat until I've put in about 3 jugs. served me well for 13 years of my speed.

I know others around here ended up doing the same to avoid worrying about ratios.

Since the oil cooler hose is towards the bottom of the engine, can I drain it from that to get more out? Or should I drain it from the radiator still? Also, the petcock loosens most of the way and then spins, is it captive or do I need to pry it out? I broke it on my first car years ago and I'm a little traumatized from that lmao

 

[Enki]

If it spins you can probably just finger pull it out the rest of the way. I have a KoYo, so I don't recall if it's captive on the stock one but it very well might be.

No matter how you try to drain it, there will be fluid left over in hoses, period. I wouldn't bother with trying to get every last drop out, and rather just keep doing what you're doing flush wise but turn the heater on to cycle that shit out too.

 

[Awafrican]

Since the oil cooler hose is towards the bottom of the engine, can I drain it from that to get more out? Or should I drain it from the radiator still? Also, the petcock loosens most of the way and then spins, is it captive or do I need to pry it out? I broke it on my first car years ago and I'm a little traumatized from that lmao

pretty sure it's captive, it's been a while. I wouldn't be forcing it, it's not a great drain.
you could always pop off the lower rad hose