Vacuum Leak Elusive
Thread Starter
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Senior User
Joined: May 2004
Posts: 392
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From: Las Vegas, NV
Vacuum Leak Elusive
I am trying to locate a vacuum leak on my '99 SHOC so my A/C will continue to blow out the front panel while under load. Currently it keeps going to the defrost. I also suffer from a low idle.
While trying to find the vacuum leak, I thought I narrowed the problem down to air leaking through the Electronic Vacuum Regulator (EVR). After a fellow FTE member told me that the voltage needed to be applied to close the valve, I tested the EVR with the engine running, but it still leaked air into the vacuum lines. So I replaced the EVR and the new one does the same thing.
I checked the voltage across the EVR with the engine running. There is around 12 volt across the connector and using an AC meter I determined there is an AC component which makes me think it is getting a pulse width modulation. But I don't know if it is the correct signal it should be getting.
With the engine running, will the EVR normally allow air back into the vacuum source lines?
When I put a vacuum on the manifold connection for the EGR and A/C system, it will not hold a vacuum at all. When I plug the source line to the EVR, the vacuum will reach to about 2 in.mg. with a lot of pumping and will drop to zero over a few seconds. With the vacuum line to the EVR and the Vapor Management Valve plugged, it will go well over 20 in.mg. and hold forever.
If anyone has some insight for me, please let me know.
While trying to find the vacuum leak, I thought I narrowed the problem down to air leaking through the Electronic Vacuum Regulator (EVR). After a fellow FTE member told me that the voltage needed to be applied to close the valve, I tested the EVR with the engine running, but it still leaked air into the vacuum lines. So I replaced the EVR and the new one does the same thing.
I checked the voltage across the EVR with the engine running. There is around 12 volt across the connector and using an AC meter I determined there is an AC component which makes me think it is getting a pulse width modulation. But I don't know if it is the correct signal it should be getting.
With the engine running, will the EVR normally allow air back into the vacuum source lines?
When I put a vacuum on the manifold connection for the EGR and A/C system, it will not hold a vacuum at all. When I plug the source line to the EVR, the vacuum will reach to about 2 in.mg. with a lot of pumping and will drop to zero over a few seconds. With the vacuum line to the EVR and the Vapor Management Valve plugged, it will go well over 20 in.mg. and hold forever.
If anyone has some insight for me, please let me know.
Post Fiend
Joined: Jan 2003
Posts: 9,748
Likes: 16
From: Connecticut
One of my posts from the Ranger Forum might help you figure out some more options:
https://www.ford-trucks.com/forums/s...53&postcount=6
NOTE: The A/C vacuum reservoir tank and bracket is located either on or beneath the RH front fender splash shield.
https://www.ford-trucks.com/forums/s...53&postcount=6
NOTE: The A/C vacuum reservoir tank and bracket is located either on or beneath the RH front fender splash shield.
Thread Starter
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Senior User
Joined: May 2004
Posts: 392
Likes: 0
From: Las Vegas, NV
Thanks for the insight in your post, but I don't think there is a leak in the A/C portion. Using a Mighty-Vac, I put a vacuum on the line feeding the resevoir tank and it held a strong vacuum for over 5 minutes without any measurable loss. So unless there is a check valve I am putting the vacuum onto, I don't think the A/C system is the problem.
Senior User
Joined: Jul 2004
Posts: 141
Likes: 1
From: Il.
great fix, i have replaced many plenium boxs for this problem. i have passed this fix on to a active Ford tech. am sure he will appricate it.
PS. i have been told thid is not a Ford problem only, was told The bowtie people have the same design. (may not be right though.)
PS. i have been told thid is not a Ford problem only, was told The bowtie people have the same design. (may not be right though.)
