Unobtanium Vacuum Check Valves and You
I've been working on my 1971 Lincoln Mark III for about 9 months now. I try not to write anything that is already out there, or present fluff - but lets talk about the Vacuum Check Valves on the Lincoln.
Here's the part number from the check valves I removed from the vehicle: P-85595-69
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There isn't much to be found on the internet about these, and for all I know, these are original ford parts that were superseded by simply and more plentiful part that do the same thing.
Why was I messing with them anyways?
I noticed that my locks weren't locking well - even after I cleaned up the electrical bits in the switches.
Under heavy throttle I was losing my blower through the HVAC.
I had tested all of the reservoirs with a vacuum tester/brake bleeder pump and they all held plenty for as long as they should.
The Test
I yanked out the check valves and find varying behaviors between them. The two inline barbs are straight pass throughs; air flows freely. The barb on the top is supposed to be a one way valve such that vacuum is available to your reservoirs and the devices they support. This means when the engine is idling, there's a good amount of vacuum - so the vacuum canisters should build negative pressure, assuming the one way valves were in good shape. Such was not the case for a few of mine.
I simply plugged one side of the straight through path and blew through the hole to test if air would come out of the top, and then sucked the opposite direction to see if it would flow. One of mine was good. One allowed free flow in both directions and the other must've failed shut.
The Not-So-Original Fix
I ordered 4 of these Evil Energy one way check valves - 1/4 inch inlets. In addition, I've been using the Evil Energy Vacuum Hose to got with these. In my case, the above part P-85595-69 was a tee and one way check valve all in one. Instead of doing it this way, I place one inline check valve with the arrow facing the intake source of the vacuum. Then, I simply tee'd off using a plastic vacuum tee between the accessories and the vacuum canister and then connected the one way valve to the tee with another section of hose.
This fix isn't for everyone, especially if you want to keep this a show car or all original, but in my case, I just wanted my accessories to work. I hope this helps.
