replaced vac switch still have hissing whats next

bscirep · Post by **bscirep** » Thu May 28, 2009 4:22 pm

so i did the switch replacement and didnt fix anything hissing still coming from dash air still coming out of vents. anybody do the full setup and have any pointers for me

Post by **HenryJ** » Thu May 28, 2009 4:40 pm

Which switch did you replace and where is the hissing coming from?

bscirep · Post by **bscirep** » Thu May 28, 2009 4:42 pm

the t-case three prong vac switch, hissing from dash, hissing dies down under acceleration but is quite loud at a stop

Post by **HenryJ** » Thu May 28, 2009 4:45 pm

See if you can narrow it down. A length of tubing from your ear to the suspect area can be helpful in finding the source. Check around the HVAC selector switch.

Did you have a leaky T-case switch?

bscirep · Post by **bscirep** » Thu May 28, 2009 5:04 pm

yea when i changed the switch it had fluid in the line but i didnt see any in the line under the hood, gm fixed it three times under warr. but i havent driven the car in about a year and a half and it is now out of warr. the last time it was fixed i was told that the fluid had made it to the control head if this is the case what would i need to do from the control down, what parts would need to be replaced what parts could be cleaned and reused

Post by **HenryJ** » Thu May 28, 2009 5:32 pm

The first thing you need to do is figure out how to remove the vacuum reservoir. It is inside the left front fender and may require its removal? That is where the fluid is likely to have pooled and continues to contaminate the system. You have to clean this or replace it as it is a continuing problem.
Then you will probably need the selector, and maybe even all the slaves? You will just have to follow the trail. Plastic parts could be cleaned. Any rubber parts that have been contaminated will probably need replacement. If not now eventually when they deteriorate.

Not a cheap project IIRC. $1600 comes to mind.

I would say you would be money ahead to buy the Helm manual before you dig in this deep.