I knew I had a bad thermostat gasket, and it was making the engine overheat really bad. So I changed that last night. No more overheating. But I was out driving today and I hear the same periodic hiss that I though before was coolant hitting the block. I know the seal is good now, as my cooling system works very well. Never over 200. It smells faintly like coolant, but thats probably from before, it's not really obvious now. Any ideas what this hissing is?

 

just a thought, but have u had your ac on? could it just be condensation hitting the manifolds?

 

The A/C doesn't work, so I keep it off. It's needs a charge, but at the moment I know thats not it.

 

Have you checked the circulation of the coolant after installing the thermostat? Open your radiator cap when the car's motor is cold and watch the circulation of the water/coolant. Also did you make sure your thermostat was positioned correctly? These are just a few thoughts from past expieriences.