When I turn the ignition key to the run position, without starting the car, there can be a szchiist noise from under the dash. This lasts for just a second and sounds as though a motor is positioning something or perhaps air moving into a resevoir. I noticed this sound after replacing the motor for the heater fan but don't know if it is related. If I turn the key to off and then back on, the noise is unlikely to repeat a second time. But, some time later, the noise will repeat. Any ideas ?
Thank you.

Trust me, I'm 99% sure it's your fuel pump priming the system and it is normal. I will not start my car until I hear it. You probably were just listening very closely after replacing the fan motor.

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'93 244: 'A' cam 4 deg. advanced, 25/22 sways, custom heim endlinks, poly bushings, and a lot more styling customization than I care to recount.

I could be completely off but...
I'm thinking its the silly little valve that regulates the vacuum to the heater controls. Although this usually happens when the car is turned off, the "shlizst" sound and location and your description of air pressurizing seems to be tipping me off. It will happen very briefly when the car is started, or sometimes you can hear it when accelerating and it's stuck open. Extra vacuum from acceleration will close it.

The valve I speak of is located on top of the manifold with a 1/2 piece of tubing leading to a white plastic valve about two inches long. From the valve, a goofy rubber plug with tiny metal tube leads to a 1/8" piece of long vacuum hose leading into the firewall.

If it's this valve- which you can remove and blow into- it should only allow air in through one side. IPD started carrying them not long ago.

Pretty sure this is how this thing works. Forgive me if I had a detail wrong!
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89 245 'loaded' with a Great Pyrenees

Do you know what that valve is called? I did not find it at IPD and I need one.
TIA

Its called a vacuum check valve, ie. only lets vacuum go one way so the reservoir under the heater assembly doesn't suck air when the engine is shut off or when it is at full throttle. One side is black, the other is white. These can be picked up at most local parts stores.

Hope that helps!

jorrell
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92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!

I knew someone would need one of those goofy things, whether it was the original poster or not!

Didn't know they were available at regular old parts stores?

~jason
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89 245 'loaded' with a Great Pyrenees

If the noise is more like buzzing or arcing, your fuel pump relay is about to fail. It is located on the firewall behind the glove box, if that is where the noise is coming from, there is a good change that is the problem.

jorrell
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92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!

Fuel pump pressurizing the system?

Ron
93 245
near Brantford, On,Can

Thanks for the responses. Fuel pump pressurizing the system seems likely. I will see if I can find the relay though. The vacuum controls for the vents seem to be operating correctly.