Missing check valve?
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Elder User
Joined: Nov 2015
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From: Bedford, Va
Missing check valve?
I drive a '94 E-150 conversion and noticed the usual symptom of the dashboard air flow diverting from dash to defrost when pulling a hill, long period acceleration, etc. I was testing to isolate a vacuum leak and noticed that I couldn't find a check valve anywhere on the supply line to the reservoir tank. The source line came from a shared block on the intake manifold directly to the tank.Everything looks factory stock, no monkey repairs. I picked up a Doorman generic valve but it passed air from either end so I didn't use it. My question is, did Ford ever release a version without the valve? Doesn't make sense to have a reservoir without one or have they incorporated it into a fitting that doesn't look like a short stack of quarters with nipples on both sides? 
Elder User
Joined: Mar 2014
Posts: 906
Likes: 1
I drive a '94 E-150 conversion and noticed the usual symptom of the dashboard air flow diverting from dash to defrost when pulling a hill, long period acceleration, etc. I was testing to isolate a vacuum leak and noticed that I couldn't find a check valve anywhere on the supply line to the reservoir tank. The source line came from a shared block on the intake manifold directly to the tank.Everything looks factory stock, no monkey repairs. I picked up a Doorman generic valve but it passed air from either end so I didn't use it. My question is, did Ford ever release a version without the valve? Doesn't make sense to have a reservoir without one or have they incorporated it into a fitting that doesn't look like a short stack of quarters with nipples on both sides?
the short answer is no, it doesn't make sense to me for any reservoir to not have a check valve back to the source. There is a huge thread on the vacuum problem you describe, all involve a check valve somewhere. jim
Fleet Owner
Joined: Aug 2010
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From: Reynoldsburg, Ohio
I believe the check valve is internal to the reservoir, the intake port runs directly to that valve via the reservoir fitting.
If the Dorman part was defective it should be returnable. Not much money I know but still aggravating to have a new part not work regardless.
Link to the lengthy but informative thread Jim mentions: https://www.ford-trucks.com/forums/1...efrosters.html
If the Dorman part was defective it should be returnable. Not much money I know but still aggravating to have a new part not work regardless.
Link to the lengthy but informative thread Jim mentions: https://www.ford-trucks.com/forums/1...efrosters.html
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Elder User
Joined: Nov 2015
Posts: 545
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From: Bedford, Va
Very interesting about the factory incorporating the valve within the reservoir. I tested the reservoir for leak, it passed. I suppose no harm in adding an external check valve. Thanks for the input. Jeff
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