1974 Lincoln Mark IV - Vacuum Issues

[74MarkIV]

Please Help...
My son has a 1974 Lincoln Mark IV with 460/ $barrel Dual Exhaust.
We are dealing with a few issues, but I figured we will try to fix one at a time.

We have a vacuum issue.
When parked the headlight lids eventually will open exposing headlights.
Sometimes when shifting into reverse from drive and sometimes from Park to Drive the gear shifter will hiss and we will have to "jiggle" the shifter to get it to stop.
Also, when we turn the air conditioner on the fan blows and it pretends to work, but it only will blow through the defrost.
I have tried researching this, I have tried finding vacuum diagrams, but very little on diagrams and a plethora of suggestions on problem.

Could someone please help remedy this problem, thank you for your time and knowledge.
Jeff B

 

[carrlos]

How did you know that you have a vacuum issue? Any fault codes?

 

[joegr]

How did you know that you have a vacuum issue? Any fault codes?

Fault codes on a 1974, that's funny.
He said by symptoms (headlight doors opening), and by sound.

 

[74MarkIV]

Exactly…sometimes I will not field those comments, but thanks for the response.
I found the problem with AC. It was a faulty line going to the door actuator.

Now, at least one problem done…just need to figure the headlights opening up while parked and the gear shifter hissing when shifting park to reverse or park to drive, or reverse to drive, and drive to reverse.

The vacuum lines on this yacht is unreal…to say the least.

Thanks for any helpful information.
Jeff B

 

[joegr]

... the gear shifter hissing when shifting park to reverse or park to drive, or reverse to drive, and drive to reverse....

I can't give you specific help for your model. I can say that you have a vacuum operated parking brake release and those usually only release when shifted into drive or one of the other forward gears. It sounds like the valve on the column that does this is bad. You could replace it and keep the auto parking brake release, or you could cap off the vacuum line going to the valve and just have manual release for the parking brake.