Hissing sound around the intake?

[Scudly]

I just started having an issue with a hissing sound. It doesn't occur on cold start up, but when the water temp hits around 180+ I will hear the hissing noise. I've checked the radiator, reserve, and oil. The car is driving fine.

I've tried to look for a vacuum leak but not felt anything or seen anything. I tried spraying some carb spray and the idle did change, but it is hard to determine which line did it or if it was the injector.

My car is a 1965 Mustang with the 5.0 EFI swap so getting behind the intake is a bit of a pain.

Thanks for the responses or ideas.

 

[stykthyn]

sounds like you have steam coming out. Check your heater connections and the water pump hoses.

 

[Scudly]

sounds like you have steam coming out. Check your heater connections and the water pump hoses.

I haven't visually seen any steam and the water temp has not gone beyond 190, but I will look at those lines.

 

[steelie4u]

sound like a vacuum leak, if the idle changes when you spray around the intake its most likely a vacuum leak from the intake

 

[stykthyn]

nvm i didnt notice earlier where you said the idle changed. definitely a vacuum leak. go tthrough all the lines one at a time. take off the upper and put a new gasket on.

 

[nero6]

I just started having an issue with a hissing sound. It doesn't occur on cold start up, but when the water temp hits around 180+ I will hear the hissing noise. I've checked the radiator, reserve, and oil. The car is driving fine.

I've tried to look for a vacuum leak but not felt anything or seen anything. I tried spraying some carb spray and the idle did change, but it is hard to determine which line did it or if it was the injector.

My car is a 1965 Mustang with the 5.0 EFI swap so getting behind the intake is a bit of a pain.

Thanks for the responses or ideas.

Spray some directly around each injector if you are having trouble tracking it down. This will rule out the seals on the injectors. This was the last place I had thought to check to track down a hissing noise as well. The rubber seals around the injectors were old an hard. Sprayed some throttle body cleaner around a few of the injectors and the idle immediately changed.

 

[Scudly]

nvm i didnt notice earlier where you said the idle changed. definitely a vacuum leak. go tthrough all the lines one at a time. take off the upper and put a new gasket on.

Why would it only occur when the engine warms up though?

Take off the upper intake? I still think the gasket is less than a year or two old... but okay.

 

[stykthyn]

if its that new then dont worry about it. just listing all the things I had to do to track down my intake leak. turned out a bolt was missing.