Vacuum Leak?
Thread Starter
Le Mans Master
Joined: Mar 2000
Posts: 9,127
Likes: 2,326
From: Pottsville, PA. USA Home Of America's Oldest Brewery Yuengling
Vacuum Leak?
My 75 convertible has had a hissing sound somewhere in the dash. My a/c controler won't change the doors or have any air flow out of the vents. I made up my mind that I was going to find this today.
I took the top dash pad off along with the speedo/tach panel, center gauges and map pocket panel. Now I plugged the hose from the headlight switch and started the car. I could hear the leak but couldn't find it. I traced the hoses from the a/c controler and found that they went behind the center ducts. I removed the center duct, defroster duct, and floor duct.
I started the car and could hear the hissing and found that the green hose was broke in half where it goes through the firewall gromment. I put a connector between the two hoses and started the car to still hear it hissing.
The black main feed hose was also broke so I fixed it. I also found the pink hose that goes to the heater box valve was also broke. After repairing it I figured out that someone replaced the heater core at one time and didn't know how to remove the heater box and just pulled it out and broke three of the hoses.
I lubed all of the hinges on the heater box doors and the temp cable. I started the car and for the first time since I have owned it(3months) the vents now all work.
When I put all of the ducts back in I sealed them up good with duct tape. I have real good air flow out of the vents.
Now that this works I will see if the a/c system holds vacuum and get the air charged.
I took the top dash pad off along with the speedo/tach panel, center gauges and map pocket panel. Now I plugged the hose from the headlight switch and started the car. I could hear the leak but couldn't find it. I traced the hoses from the a/c controler and found that they went behind the center ducts. I removed the center duct, defroster duct, and floor duct.
I started the car and could hear the hissing and found that the green hose was broke in half where it goes through the firewall gromment. I put a connector between the two hoses and started the car to still hear it hissing.
The black main feed hose was also broke so I fixed it. I also found the pink hose that goes to the heater box valve was also broke. After repairing it I figured out that someone replaced the heater core at one time and didn't know how to remove the heater box and just pulled it out and broke three of the hoses.
I lubed all of the hinges on the heater box doors and the temp cable. I started the car and for the first time since I have owned it(3months) the vents now all work.
When I put all of the ducts back in I sealed them up good with duct tape. I have real good air flow out of the vents.
Now that this works I will see if the a/c system holds vacuum and get the air charged.
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
Re: Vacuum Leak? (FeedVaal)
What a job. Nothing like the satisfaction of fixing something that has been broken for a long time. Way to go. :thumbs:
Instructor
Joined: Apr 2000
Posts: 118
Likes: 0
From: Inver Grove Heights MN
Re: Vacuum Leak? (Corvette ED)
If you want some really good help on troubleshooting 1968-1982 vacuum systems, A fellow named Frank Prow has written a 14 page "primer" on the subject. If you tell him the model year of your Corvette, he will include specific diagrams for that car. The materials are excellent and he charges $12.00 for the package whichj is maild to you. You can contact him at: http://www.vettevacuum.com
Jim
Jim
