rattle

Hi, our "new car" is a '90 Golf ! Does the rattling sound like chains rattling? Are you using gas with sufficient octane rating? The symptoms sounds like pre-ignition ping from too low octane fuel. Also don't mix fuels of different octane ratings. The octane ratings don't "average out", the resulting octane is the octane of the lower rated fuel. My car's one made for Canada and the specifications are 90 octane gas, but I run mid-grade 89 octane and it's fine.

As for the hissing, is it accompanied by exhaust noise? Then it could be a leaky exhaust system or a plugged cat converter. Get under the car while the engine in running and see if you can detect where the air is coming from. Have someone (you trust!) rev the engine to simulate acceleration and see if the hissing noise appears. I had a loose joint at the downpipe to cat that was letting exhaust air out but it sounded more like a worn out muffler than a hissing. However, the loose parts at the joint rattled too. Also hit the cat with a hammer (lightly) and see if it makes a dull sound like it's full of loose crud. If a dull sound, all the tubes inside the cat might have disintegrated. If that all checks out, when the tank is near empty, try the next grade of gas.

So my guesses: either too low octane gas or worn out joint between down pipe and catalytic converter. If it's the joint, you can buy a 2 part triangular shaped split clamp that will fit over the worn out flanges and close the joint up nice and tight.

Curious to hear what you discover.

Thanks for the tips-

I learned the octane lesson pretty early on- the car is a gas snob- I use only premium. I'm going to check out that joint today. I'll post my results.

Congrats on your "new" car. They're easy to love. Our Golf, we've had it for about eight years, has been an amazing car. We've put a hundred thousand miles on ours so far. I'd be lying if I said we haven't had any problems but about 80% of those problems I have been able to fix myself. It's a fun car to drive, plenty of power, and (in my opinion) a very nice looking car, too. The funny thing about those cars is that the better you treat them, the better they treat you.

Thanks again and happy motoring.