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When I was testing the secondary air change-over solenoid, I removed the vacuum hoses and the small blue one way check valves. Stupid me, I did not look or take a picture of the original configuration before pulling things out.
Now, I can't find a picture, illustration or video online to reference the proper sequence ( direction of check valve arrows). Moreover, the two top AI services each had conflicting answers. One said both arrows ( on those small blue one-way valves) point towards the engine manifold and the other said both point towards the solenoid.
Lastly, my 2008 E350 has the same M272 engine but it has one less vacuum hose connected to the solenoid and thus just one of those small blue one-way check valves.
I know for sure that one vacuum hose is attached to the fat solenoid hose connector, then travels straight down to the passenger side EGR. That same hose branches off and also connects to the drivers side EGR.
The thinner hose connector on the switch over solenoid is attached to a Y shaped black hose section. At that point it branches out to two different hoses. One connects to the front of the manifold and the other extends behind the secondary air pump, under the ECU and goes somewhere behind the engine or manifold on the drivers side.
QUESTION IS
Do both of the arrows on those small blue one way check valves point to the manifold or the solenoid.
Or, does one check valve arrow point in one direction and the other point in a different direction. If so, what direction for the hose that goes into the front of the manifold and what direction for the hose that travels to the back of the engine?
I removed the solenoid (seen resting disconnected above the hoses) so people could get a better view of the hoses.
Thank you
Please see the hoses with the small blue one way check valves. One goes directly into the front of the manifold, the other extends all the way to the back of the engine on the drivers side (L)
The arrows are supposed to point in the direction of intended air flow. Since this is a vacuum system, and the manifold is the source of the vacuum, then the arrows should point towards the manifold. I hope that helps.
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