Calais question

[the camel]

Howdy everyone. Brand new to the site and not very knowledgeable when it comes to cars. Looking for an answer to my dilemma.
Driving the other day and I had to brake reasonably firmly at a set of lights. On takeoff I heard an increasingly loud knocking from the front left of the car as if something was loose there. I pulled over to see a steady stream of brownish water pooling into the gutter. I filled the overflow tank but it just leaked out. I took the cap off and filled the radiator and this seems to be staying in the radiator as the car is not overheating at all and I drove a lot yesterday by necessity.
It's fair to say I'm confused. Is this something I should look into immediately? What the hell happened and why is the car running fine now? I'll send a photo ASAP.

 

[gossie]

Brownish water is all WRONG.
When did last do a radiator flush and fill with CORRECT fluid?
Depending on model it needs to be either green or red. It’s in the books and follow them as mixing coolant is a massive no no no.
Have you had the bonnet up and taken a proper look at the overflow bottle? Is it cracked or broken?

 

[the camel]

Brownish water is all WRONG.
When did last do a radiator flush and fill with CORRECT fluid?
Depending on model it needs to be either green or red. It’s in the books and follow them as mixing coolant is a massive no no no.
Have you had the bonnet up and taken a proper look at the overflow bottle? Is it cracked or broken?

Thanks for the reply Gossie. I have just been given the car by a mate...2 or 3 weeks ago...(it was his father's car and had been sitting around for 8 months). so the other night was the first time I had a good look under the hood. I wasn't kidding when I said I know nothing about cars. I'll have a good look tomorrow and get back to you. Thanks again.