Vacuum leak?

[BOBBY263052]

My 92 Ty started making a hissing noise behind the dash today. Does it with or without the heat on. Stops when you give it some gas while driving but not if you gas it in park. Sounds like a vacuum leak to me. What do you guys think? If it is a vac leak would you assume it's coming from the vac lines going to the HVAC controls? Anyone ever had this problem?

 

[jwaller]

Re: Vacuum leak?

s-series hvac controls are known to have this issue once you have the kinda time and yrs on them that these trucks do.

 

[gkrcr882]

Re: Vacuum leak?

If it goes away when you're in boost, its a vac leak. There is a bundle of conntectors that go to the back of the HVAC controls, and if the tubes arent on tight they'll leak. A word of warning: the tubes shrink over time, so it may be extremely difficult to get the control out, and theres a tem control cable located in there too that limits how far it can come out.

 

[BOBBY263052]

Re: Vacuum leak?

Besides driving me crazy, would it hurt anything to drive it this way till we get a warm day to work on it? It wont effect the waist gate opening will it?

 

[sleepy]

Re: Vacuum leak?

It won't hurt anything, my truck has been doing this for quite a while. Just too lazy to take it apart.

 

[El_Jeffe]

Re: Vacuum leak?

My 92 Ty started making a hissing noise behind the dash today. Does it with or without the heat on. Stops when you give it some gas while driving but not if you gas it in park. Sounds like a vacuum leak to me. What do you guys think? If it is a vac leak would you assume it's coming from the vac lines going to the HVAC controls? Anyone ever had this problem?

I have the exact same issue with my 92. I tried to pull the HVAC controller out this summer but it did not want to come out easily so I left it as is. I'll try another time when I have a little more time to tinker with it. It does not seem to be affecting anything for me other than annoying :rant: the hell out of me when I pay attention to it.

 

[BOBBY263052]

Re: Vacuum leak?

I try to ignore it but damn its hard to!

 

[thesyguy]

Re: Vacuum leak?

This just happened to my Sy a couple of months ago. It was the diaphragm unit that the vacuum line cluster plugs into on the back of the HVAC controls. The part was like $12 from GM. Not tough to do, but make sure the gear that it attaches to is lined up properly or the stops for heat, defrost, max AC etc. will not line up properly. You will see what I mean when you get it apart.

 

[BOBBY263052]

Re: Vacuum leak?

Cool, thanks.

 

[El_Jeffe]

Re: Vacuum leak?

This just happened to my Sy a couple of months ago. It was the diaphragm unit that the vacuum line cluster plugs into on the back of the HVAC controls. The part was like $12 from GM. Not tough to do, but make sure the gear that it attaches to is lined up properly or the stops for heat, defrost, max AC etc. will not line up properly. You will see what I mean when you get it apart.

Did you struggle to get the unit out? I had all the screws out on mine and it still would not pull out. It felt like the lines/connections behind it were too short, not letting it pull out. Is there an easier way to get to the diaphram? Maybe I didn't pull it hard enough. It felt like I might damage or break something if I pulled it any harder. Thanks

 

[thesyguy]

Re: Vacuum leak?

You do have to pull on it pretty good to get it far enough out to disconnect the cables for the flappers. Then the vacuum harness is easier to do. I know it feels like it is going to break and it is something you have to do very carefully or else you will have a mess on your hands.

 

[El_Jeffe]

Re: Vacuum leak?

You do have to pull on it pretty good to get it far enough out to disconnect the cables for the flappers. Then the vacuum harness is easier to do. I know it feels like it is going to break and it is something you have to do very carefully or else you will have a mess on your hands.

Thanks. I'll give it another shot.