<human>: Can you provide a brief rundown of the text in within 3 sentences?

So I've just seen this post: 
It reminded me of a fuckup of my own not too long ago.

Probably around 3 months ago, my girlfriend and I were driving through a nice little country valley a few miles north of where we live. Nice open roads, lots of hills and a merciful lack of cyclists. We're chilling out, listening to music and soaking up some spring sun.
I really hammer this car (A citroen C2) down a long hill, just enjoying the drive. As we ride out the bottom of the slope, there's a "thwip!" sound, followed by a crapload of ticking sounds. I drive another half mile, testing the breaks, accelerating and decelerating, changing gears, coasting in neutral. When I put it in neutral, the ticking stops. As far as I can tell, it's at the back of the car.

I pull into a little gravel area by an old water pumping station, next to a stream. I hop out and get under the car, while my girlfriend wanders off onto a grass verge.

I get round to the back of the car and crawl underneath. Bingo, beer plastic holder thingy is trapped in what I assume is the drive shaft area (I'm not too technically gifted but I know a bit)
I give it a pull and... The car starts rolling. Away from me. I'd left the parking break off. I breath a sigh of relief I'm not about to be crushed, I quickly turn to panic as I realise this car is rolling downhill... Towards the stream.

I scream my girlfriend's name at the top of my lungs, who has wandered off up a hill to take pretty pictures. Realising she won't get back in time, I, still under the car, grab hold.
In my panic, I grab the fucking exhaust. Two handed. The pain is searing, but in my panic I keep hold. Fuck. Fuck. This is excrutiating. The car is still rolling. I roll out from under it and throw the door open, grabbing the brake as the car stops, wheels at the edge of the drop into the stream. Too close.
<bot>: Went for a country drive, heard a sound, tried to be a mechanic, left parking break off, grabbed exhaust and nearly lost car in a stream.