Vintage Mustang Forums banner

Hissing sound coming from engine

330 Views 4 Replies 5 Participants Last post by  C-Woods-70
Hi there! I have a 64.5 mustang with the original 260 motor. It actually runs really well and never gives me issues. Recently I noticed a hissing sound especially when I take it on the expressway and open it up to 50 mph. Vacuum leak? If so how do I diagnose and fix?
1 - 5 of 5 Posts
Get a cheap vacuum guage at harbor freight.
Hook it to a full manifold vacuum port.
Check it on idle
Let us know the readings
Snake on a stang?
That makes it a Shelby!
  • Like
Reactions: 1
Do you hear it sitting at idle with the hood up? Not very many vacuum lines on these old cars to check. Remove the air cleaner and make sure the vacuum lines on carburetor and the vacuum tree directly behind have not came off. It would also run a little rough at idle if a manifold vacuum source were leaking.
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.