> The fluid circuit is really a closed loop. 


Yes, true. And because of this the reservoir has more or less fluid in it depending on whether the gear is up or down. If there is no venting the tank will pressurize. There is a very tiny hole in the threads on the filler cap neck. Make sure that this hole is clear. I barely tighten the cap to make sure that I don't defeat the vent. If all else fails, give this a try.

Bill,

 

You are absolutely right - How easy it is to forget this detail.  If fluid has been wetting that wee hole, then drying out (turning sticky) and attracting dirt it can eventually become plugged - Arrrrrgh.

 

Hmmmmm...... Let's say we have 3 actuators with 3/8 " rods and an 8 inch stroke and 3 actuators with 1/4" rods and a 3" stroke. Uh, pi x r**2 x length ..... Say, that's about 3 cubic inches or about 1.7 oz.  Assuming there is some air in the reservoir, it might not make that much of a pressure difference.