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Discussion Starter · #1 ·
Doors stay shut for about an hour after I shut the car off then slowly open.
Pretty sure it's a vacuum leak. Can anyone tell me where to start the diagnosing process? Appreciate any help or suggestions. Thx!
 

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It's most often the vacuum motor seal, sometimes the internal vacuum motor diaphragm. I start with a tubing clamp (vice-grip will work if you don't have a tubing clamp) and clamp off the side that would provide vacuum to the closed position somewhere near the vacuum motor. if the doors go up that vacuum was lost through the vacuum motor. Its hopefully the seal under the rubber accordion boot. there's a kit to replace that. If it's the diaphragm, it's pricey to get a rebuilt replacement from that guy in Canada. Critter Creek Cougar Restorations – Headlight Vacuum Actuators If that passes the test start moving back towards the light switch, first do the same test on the other side of the vacuum bypass valve (somewhere near the windshield washer reservoir), then at the firewall going to the light switch. Also check every vacuum tube on the "closed" supply for cracks or loose connections.
 

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Or you could just unlatch one of the 2 flat coil springs that assist the doors to raise when vacuum is lost. There is one on either side by the door connected to the common shaft. The doors will stay down with no vacuum present, but still operate normally when the lights are turned on. I saved $535 that way :cool:
 

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On '70s it's a common hack to loosen the stock springs 3/4 a revolution by allowing the bent end to come off the OEM retaining peg and come to rest on the screw that protrudes into it's path. The bent end of the spring will rest there nicely there and this allows just enough tension to come off the spring to keep the doors from creeping up over time when the engine is off.
 

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70 Cougar 351C 4 barrel with 4 wheel disks custom interior getting new paint mild cam AOD trans
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I spent a little more money and maybe time but I used a kit that coverts them to electric they work great and open and close together
 

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Discussion Starter · #8 ·
It's most often the vacuum motor seal, sometimes the internal vacuum motor diaphragm. I start with a tubing clamp (vice-grip will work if you don't have a tubing clamp) and clamp off the side that would provide vacuum to the closed position somewhere near the vacuum motor. if the doors go up that vacuum was lost through the vacuum motor. Its hopefully the seal under the rubber accordion boot. there's a kit to replace that. If it's the diaphragm, it's pricey to get a rebuilt replacement from that guy in Canada. Critter Creek Cougar Restorations – Headlight Vacuum Actuators If that passes the test start moving back towards the light switch, first do the same test on the other side of the vacuum bypass valve (somewhere near the windshield washer reservoir), then at the firewall going to the light switch. Also check every vacuum tube on the "closed" supply for cracks or loose connections.
Thanks for the reply, very helpful...
It's most often the vacuum motor seal, sometimes the internal vacuum motor diaphragm. I start with a tubing clamp (vice-grip will work if you don't have a tubing clamp) and clamp off the side that would provide vacuum to the closed position somewhere near the vacuum motor. if the doors go up that vacuum was lost through the vacuum motor. Its hopefully the seal under the rubber accordion boot. there's a kit to replace that. If it's the diaphragm, it's pricey to get a rebuilt replacement from that guy in Canada. Critter Creek Cougar Restorations – Headlight Vacuum Actuators If that passes the test start moving back towards the light switch, first do the same test on the other side of the vacuum bypass valve (somewhere near the windshield washer reservoir), then at the firewall going to the light switch. Also check every vacuum tube on the "closed" supply for cracks or loose connections.
Thanks for the suggestions. I appreciate it.
 
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