Auto trans vac lines?
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Joined: May 2011
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Auto trans vac lines?
Just wondering...There are two AT vac lines on my truck, one runs to the modulator valve and the other has never been hooked to a vacuum source at engine.
When I bought this truck 15 years ago it was unhooked.
Anybody know its function and why someone would disconnect it?
73 F100 369/90
When I bought this truck 15 years ago it was unhooked.
Anybody know its function and why someone would disconnect it?
73 F100 369/90
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
This is an early-style dual-vacuum valve. Like all modulator valves, it has one line that goes to a manifold vacuum source. The second port goes to the same vacuum signal that goes to the EGR valve (in other words it should tee just upstream of the EGR valve).
The purpose of this was to maintain a relatively constant vacuum signal at the modulator valve when the EGR valve opens - this wasn't retained for later years. If your EGR setup is long gone, then just plug it off.
The purpose of this was to maintain a relatively constant vacuum signal at the modulator valve when the EGR valve opens - this wasn't retained for later years. If your EGR setup is long gone, then just plug it off.
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