1983 SDV HT4100 Noise

[George Woodford clc21025]

I believe I resolved the errr noise under the hood of my 1983 SDV.  The noise would occur during warm or hot weather after starting the car for the first or second time before the engine warmed up to operating temperature.  The noise sounded like a slipping belt, but with the hood raised, I noticed it was coming from just behind the distributor.  The noise would only last about two minutes.  The noise would increase in pitch by increasing the speed on the engine by moving the throttle.  What if I said it was the Vacuum Check Valve, which had a couple holes in the flat side of the nut shapped base? Maybe I hit the bullseye on the target especially when you think about what was happening with the Air Management System.

[Mike #19861]

 You may have got it. There are a number of AIR and vacuum lines that run there.

 If you can look in there, I know it is tough, but check the condition of the AIR lines. They can rust trough causing a noise and at worst an exhaust leak.

 Mike

[George Woodford clc21025]

The valve has a heavy layer of black dirt and oil looking inside the bottom hole.  I noticed oil and dirt had accumulated around the area of the valve.  The original valve appears to be made to fail after a period of time.  The new valve looks identical to the old one, but it does of the spots on the flat sides of nut shaped base.  These spots appear to be there to break open under some pressure.

[Mike #19861]

 That sounds like the aspirator valve to the 3-way catalyst. They do burn through on occasion and the result is exhaust getting through into the AIR system. That can cause the noise.

 Also, the divertor valve on the AIR system can cause this noise buy allowing air from the pump into a corroded pipe. When the pump bypasses, then the noise stops.

  Mike