Hello. I have a 95 f150 5.0 4x4. Had my AC reacharged and noticed when on highway it would cut to defrost at 1600 rpm. I noticed the white vacuum line under hood was cracked. I cut it back put on and I replaced every single vacuum line under hood with silicone upgraded to 96 vacuum reservoir. Removed smog pump and all those lines are removed and capped at there solineds to prevent check engine light. It's alot better but does it under heavy load around 2100 rpm. Do I need to start looking at lines under the dash? Thank you

 

I've had the vacuum switch itself start leaking like crazy...

They can pop apart, or lose a seal.

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Does the vacuum reservoir hold a vacuum?

 

Yea it holds a vacuum. This design doesn't incorporate the reservoir for HVAC system. It's just for EGR,smog and cat fresh air. (I might actually plumb it in to it).I removed and capped everything except EGR. No leak. Old coffee can was not looking healthy. I see two black lines go in hvac by passenger side firewall. Do brake bleeder vacuum pumps work for testing vacuum leak? I tested manifold and throttle body no leak.