Troubleshooting

Air leaks

If you suspect that your engine might be leaking, spin the drive shaft with your fingers while Grabbing some data.  The pressure should be greater than 3 kPa, peak to peak.  If it is closer to 2 kPa, then you probably do have a leak.  Attempt to isolate and repair the leak, using the above test as an indicator of when you have fixed the leak.

Sometimes you can find a leak by connecting a tube to one of the helium ports, opening the associated pinch valve, and blowing air into the engine: leaks can sometimes be detected by putting a wetted finger near the engine, or by using a small feather.

If the bolts that hold the engine together were to loosen (unlikely!), this could cause an engine leak.  You can detect this by gently pressing on the top of the engine (when the engine is cold!), to see if additional pressure seals the leak.  If the bolts are loose, tighten them to finger tightness, and then 1/2 turn more.  Do not over-tighten the bolts.