Has anyone changed from 5W-20 to something else?

[Dekeman]

I'm now hearing a hiss type of sound in there, as I'm getting informed here and listening a little more carefully. With the hood open, I hear a release of air, like air brakes, when the engine shuts off. Intake leak?

[MagicRat]

Intake manifold vacuum drops to zero as soon as the engine is shut off,so there should be no 'hiss' there.
However, there are two vacuum resivoirs that will hold their vacuum when the engine is switched off. One is the brake booster. The other one is connected to the interior ventilation system. If these systems are leaking, they will hiss briefly when the engine is shut off.

Wait a minute after the engine is switched off, then step on the brake pedal. You should be able to get 1-3 'power' brake applications before the pedal gets hard. If not, then the brake booster is not holding vacuum as it should. This is a safety issue, since this reserve is designed to give you some power braking ability even if the engine stalls.

If the brakes are good, then it's likely a leaking vacuum hose elsewhere. Ideally, you will want to stop the leak because it can upset the idle speed, affect the function of a vacuum controlled device and likely will eventually get worse.
Try listening carefully around the engine or under the dashboard for a whistle/hisswhen the engine is idling. Hopefully it's just a loose/leaking vacuum line.

[wiswind]

Also, the Air Conditioning system makes some hissing sounds after the vehicle is shut down. This is the refrigerent in the system.
Completely normal sound.

[Dekeman]

Originally Posted by MagicRat

Wait a minute after the engine is switched off, then step on the brake pedal. You should be able to get 1-3 'power' brake applications before the pedal gets hard. If not, then the brake booster is not holding vacuum as it should. This is a safety issue, since this reserve is designed to give you some power braking ability even if the engine stalls.

If the brakes are good, then it's likely a leaking vacuum hose elsewhere. Ideally, you will want to stop the leak because it can upset the idle speed, affect the function of a vacuum controlled device and likely will eventually get worse.
Try listening carefully around the engine or under the dashboard for a whistle/hisswhen the engine is idling. Hopefully it's just a loose/leaking vacuum line.

Brakes are as solid as ever. I'm pretty anal about this in particular.

Originally Posted by wiswind

Also, the Air Conditioning system makes some hissing sounds after the vehicle is shut down. This is the refrigerent in the system.
Completely normal sound.

I'll get a close listen to the A/C on the next shutdown I have a chance to be here for (my wife drives the 'star). Thanks for the good tip- it helps a lot to narrow down possibilities!