Some time ago my trim pump tanks where leaking and the single bolt tanks would just not stop leaking not to mention the yellow cap was leaking also. Well I replaced the single bolt tank with a newer 4 screw mount tank and the tank itself stopped leaking. But the yellow caps where still leaking. After trying a few different things the best answer was buying a flat sheet of cork and cutting a full circle "gasket" and putting it in the cap and Walla! no leaks.

Don’t those caps need to breath or vent?

yep..

Yes, they are supposed to be vented ... that is why they (Merc Racing) tell you to take the seals out of them prior to use, when they are new - they have a seal/plug in them that is supposed to be removed, when new. The new version yellow caps have a better vent system and a company called Turbo Sonic made (maybe they still do make them) "no leak" blue caps with weighted vents. Last I knew they were offering them in a variety of colors instead of just blue.

Interesting, I've got the same problem... anyone have a link to the newer style tanks/reservoirs?

The yellow caps that you get with the new tanks are worse than the old ones. There isnt any real threads in the caps to speak of. You can almost snap them on. So man do they leak. By putting the cork in there it aids in sealing up the leak. Remember oil is alot thicker than air. Everything has been working just fine. The tanks have completely stopped leaking and every once in a while you just give the cap area a qwick wipe. As regards to where to buy the new style tanks, I found them on e-bay at a place in Jersey. Sorry dont remember the exact address. They where about 4 dollars more than the one bolt syle. Im no stranger to the workings of fluid supply systems. Have been keeping aircraft in the air for 30 years. Heck boats are easier.

Do these work? http://www.cpperformance.com/p-13281...itor-caps.aspx

I had the turbosonics on my 4 pumps. I really had to crank them down to keep from leaking. Just snug and none would seal around the o-ring and all leaked worse than the yellow caps. Must be a flaw in the clearances somewhere, thus good and tight to make them leakproof.

I also replaced all the center bolt reservoirs for the 4 screw types. Didn't like how the old ones twisted. Everyone of those leaked at the tank seam where the top and lower halves were fused together. Put my old ones back on and nomore leaks. I did try to reseal the joint with some 5200, but haven't tried them.