Wanted/needed:
- Tricks of the trade in search of a cockpit-underdash vacuum leak.
- Most likely candidate(s) as to the problem

1980 450SEL 150k miles.

Just started hearing a faint high pitch noise after shutdown. It disappears in a matter of 15-30 seconds. Depressing the push buttons of the a/c panel does affect the noise. It all makes sense to me as a vacuum leak as the vacuum tank gets pulled down to zero due to the leak.

Looking for high pressure leaks is easy, spray soapy water..... Vacuum leaks, ugh. Short of putting a constant vacuum on the mainline from the engine compartment and then clamping off lines until I get silence (and a stethoscope helps too). Any other tricks of the trade that can help would be appreciated

I am on my knees praying to the god of busted knuckles that it's not the diaphrams wayyyyy up under the dash.

Thanks.

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S, J.R. Brown
2000 G500 LWB Obsedian Black
2005 Toyota Tacoma Access Cab Off Road Sport
1993 Volvo 240 Sedan Anthracite
1980 450SEL Champange (owned it for 15 years. Great car)
1986 280GE LWB Anthracite (Sold it and kinda wish I hadn't)