air in oil lines

[joewillybob]

My 71 T350 gets air in the oil lines. Heres how it goes, when I run the engine and hold the pump lever in the fully open position, the bubbles are forced through and all seems well. However, when I release the lever and operate it with the throttle, as in blipping the throttle, when the revs drop, bubbles appear in the lines near the fittings at the base of the cylinders. Holding the lever on the pump fully open will again purge the lines of air. Bad oil pump or bad fittings on the lines? Is there a correct way to flush out the lines/fittings without destroying things? The fittings do not seem to be removable. Thanks.

[H2RICK]

AA) If the bubbles are appearing ONLY at the ends of the lines where they bolt onto the cylinders or cases then you PROBABLY have stuck/damaged check valves in those banjoes on the ends of the lines.
The check valves are probably stuck open allowing the air from the crank chambers and/or the intake tracts to be forced back into the lines.
BB) Another possibility is bad/missing sealing washers on those banjoes.

[cpt137]

I went thru all that, replaced the valves, cleaned them, checked for leaks, still got air. I knew there had to be a leak somewhere I just couldn't find it. I finally took some liquid electrical tape and painted the 1 into 2 joint and have had no leaks since. At least on mine, and probably most others I don't think the valves have anything to do with it. I think there is a very tiny crack or hole some where in the joint allowing air to get in. I think any type of sealer, paint or whatever around the joints going into and coming out of are going to solve your problem. And, it will cost you nothing to find out.

[oldjapanesebikes]

I find it interesting that the twins share a similar design having the Siamesed oil feed with the one into two split oil lines, so it becomes an additional potential point of failure the triples don't have. Sounds as if it's an additional thing to check for, if you happen to have a one with this configuration.

[johnakay]

if you can still get new triple oil pipe lines ,why not convert these to fit.
its something worth looking into?

[oldjapanesebikes]

if you can still get new triple oil pipe lines ,why not convert these to fit. its something worth looking into?

Wouldn't be an easy conversion at all I'm afraid John, and new oil lines are not available for any of them that I'm aware of. I suspect it will become a huge problem in 10 years time as the plastic will by then be well over 40 years old, but I'm not going to worry about it now.

[johnakay]

plastic tubing is not a problem.
I was thinking of the oil line valves etc.