Starter Fluid to Check for Vacuum Leaks?

[350SL4spd]

Someone mentioned that you could check for vac leaks in a gasser by spraying starter fluid where you thought you had a leak. If you had a leak the idle would increase for a second.

Sound solids right?

I'm trying to diagnose a bad idle in my '75 450SL (D-Jet) & one thing I'm trying to eliminate is a leaking intake manifold gasket. I tried the starter fluid trick (carefully, mind you) & I didn't get a higher idle anywhere, but when I sprayed a bit (just a bit) in the intake itself the idle DROPPED. Is it flooding? On a drop of starter fluid? Doesn't sound right to me. Can someone give me a reality check?

Maybe a hot meal will set my head back on my shoulders...

[Tomguy]

Usually the fluid will cause a stumble and NOT an increase. Makes the mixture too rich. It might be difficult to notice on individual runners if the leak isn't serious. If your intake manifold were leaking at the heads, you'd have coolant loss most likely. It's usually at the manifold halves where it leaks.

[Matt L]

Try WD-40 for this task. It's a whole lot safer, and works well.