Coolant replacement question. Engine not retreiving.

[ST185]

Just had a mare changing the coolant on my partners car... as i drove up to paraparaumu on friday during peak hour and the temp needle hit the top and i think i saw steam coming out of the front - luckily i was at the end of the queue and once the radiator got a bit of wind into it the temp dropped back down to normal. Found out later she had been topping it up with water so was probably diluted somewhat.

30 minutes job turned into about 1.5 hours.
First time ive ever done it so i have a couple of questions.

Used the small bottle of stuff first into the coolant thats supposed to loosen rust and other crap in the radiator - went for a drive for 20 minutes with the heater on full as the bottle suggested.

I managed to unscrew the plastic bolt underneath the car and the fluid started dripping out slowly..... it was going too slowly so to speed things up i turned the car on again and put the heater on (thinking if the engine needs too cool itself it will suck the coolant from the container).. after about 5 minutes of waiting the container was no less full. I tried everything - heater on full, aircon on, everything to try and get the engine to use what was in the container - i could even see the engine temp inside the car rising past halfway but still it wasnt taking it

Turned the engine off and opened the radiator cap (remembering something about physics needing the air pressure at the top to allow water to flow through) this didnt result in any extra flow of coolant coming out of the bottom. Got sick of waiting and pushed the hose into the radiator cap and flushed everything else out - so now only clear water was coming out the bottom at a steady pace. I unscrewed the coolant container and tipped what was in it out and plugged the hose back in.

I refilled the radiator directly through the radiator cap with the new coolant to the top and poured the rest into the container.

1. Why wouldnt the radiator suck coolant from the container ?? maybe thats why it was overheating in the first place (has this happened to anyone else ?)

2. Coming out of the container are 2 hoses -1 to go directly to the radiator and the other goes nowhere (maybe a hose to release coolant if the container gets too full???) Or is this hose supposed to be connected to the engine too - to circulate the coolant ???

Im confused.
Any help appreciated.

[Caveman]

First off your problem with overheating is probably a faulty fan. Even pure water shouldn't overheat in traffic if the fan is working properly. Check the fan switch, fuse, relay and fan.

Container? Overflow bottle?

[kingcorolla]

This 'container' you speak is the radiator overflow bottle. It is used to catch excess coolant from the system when pressure gets too high, system gets over 13psi pressure, the sprung seat in the radiator cap will lift, bypassing excess coolant/pressure into the overflow. This does not happen often.
When the engine cools down after shut-off, coolant cools down therefore pressure is reduced inside system. This is were you really start to see these tricky bits of kit in action! The radiator cap has what we call a vaccuum valve, and when the pressure is at atmosphere inside the system, this vaccuum valve opens , and sucks the lost coolant from the overfow back into the system to fill the gap!

the other hose on the overflow isnt ment to connect anywere.