I went ahead and tried doing a radiator coolant flush this morning. I dumped a can of radiator flush stuff into the radiator as per the instructions, ran the car for 10 minutes, let it sit for half hour, and then flushed everything out through the coolant drain on the side of the engine. I didn't measure exactly, but about 6 litres must have came out. I refilled the radiator with a 50/50 mix of distilled water and antifreeze and started the car again. I was only able to get 3-4 litres into the radiator before it was at the top. I ran the engine for a few minutes but then it began to overheat and I shut it down again. When I pulled the radiator cap off coolant came gushing out. This never happened before I flushed it...

Any ideas? I'm a big mechanical noob, sorry

 

okay, remember that a cooling system is a pressurized system. If the system was still hot, it was under pressure when you took the cap off, thus coolant spilling out. the overheating sounds its like it's b/c of air in the system. There should be a place for you to drain the old coolant from the block/housings as well.

What you should do is burp the sytem.. When engine is cold, take off the radiator cap, start the car and watch the bubbles come up. squeeze the upper radiator hose to induce the burping. Do this for a couple of times and all the air should come out.