Question abot Vacuum lines 87 GN

[turbobeast707]

I have been having some vacuum problems and I am trying to narrow down the possible leak my 87 GN analog dash.

1. I found two vacuum lines that run under my A/C unit in the engine bay but didnt find them under the dash in the car, are they supposed to be there and if so what are they for? (and my hobbs switch is connected and teed into my map sensor.)

2. My vacuum reading on my boost gauge is at around 10-12 what sould the vacuum read at idle?

3. What is the best way to run a vacuum leak test and how to perform it?

Thanks in advance, Im learning alot from you guys on here... I apreciate all of your information.
Isaac.

 

[rickyracer01]

I'm no expert but i usually use a can a brake cleaner and spray down any area where a leak could be possible. manifold, throttle body, EGR valve and hoses. i have a 87 GN also so when i get to the shop later on today i will take a look at my AC unit to see if i can tell where the vacuum lines lead to. also like i said no expert here but i personally would not t-off anything to a map sensor. that is a crucial sensor and there are many other location you could find vacuum from for that switch. if that switch were to leak even a little it would throw off the map sensor signal due to not getting accurate readings of vacuum/boost. also at idle my vacuum gauge reads between 19-21.

 

[turbobeast707]

Ok thanks.
I guess if im only reading 10-12 I do have a vacuum problem..
Thanks
Isaac

 

[rickyracer01]

Are you sure your gauge is working properly?

 

[trixdout]

How man miles on the engine? Check the seals on the shaft that the tps sensor and throttle arm sit on. Those seals tend to go and usually after you connect all your vacuum hoses and still have an issue, it will be there.

Sent from my iPhone using Turbo Buick

 

[87gninpa]

Do you have a larger cam in the car? Typically with a stock camshaft and healthy engine you should see 16-18 in at idle.

As far as the other leaks, check each line with a mity-vac to find any leaks. Once all of the lines/hoses are deemed good, make sure you have no leaks around the vacuum block/intake manifold/injectors/throttle body.

 

[turbobeast707]

there is about 1000 mi on the engine since build has a 206/206 billet roller cam. Vacuum gauge is working properly I pulled it out and tested it in my other car and worked fine.
Isaac

 

[TurboTdr3.8]

With a larger duration cam the vacuum will be lower at idle , that sounds about right as mine is about 10# to 12# idling in gear with a 220/224 cam

 

[turbobeast707]

ok thanks. So I should be fine at 10-12 at idle..
Isaac

 

[turbobeast707]

but does anyone know about any vacuum lines that run under the AC unit?
trying to decide if I should just eliminate them cause I cant see where they go unless I remove the AC unit...
Thanks, any info is more than I have now (none)....LOL
Isaac.

 

[Phoneguy]

The vacuum hoses under the AC go to the heater/AC control in the dash, they control the vents.

Bryan

 

[earlbrown]

and the charcoal canister if you still have one. Pop the check valves off and see if they still work while you're poking around in there too.

 

[GNRick]

Smoke test works for me. If you have a scan tool, you want to see 128 +-10 for blm. I bought my smoke tester off Craigs List for $300. They are $1000 new. I've heard you can also use the cheaper ones that they sell for magic shows.