Vaccum Power Door Locks 4000s

Old 11-01-2005, 03:04 AM
1st Gear
Thread Starter
Join Date: Nov 2005
Location: Vic City
Posts: 47
Default Vaccum Power Door Locks 4000s

It isn't much of a big deal, but it's nagging me everytime I lock my doors or have to reach over to let other people into my car. I was told by my mechanic that the power locks were powered by some sort of vaccum system which has some sort of leak in it somewhere. When I lock or unlock my doors from outside, I can hear the motor running for quite a while or until I start the car. Does anyone else have the same sort of problem? How much will it cost me to replace this sort of thing, or can I do it myself?
Old 11-01-2005, 07:55 PM
1st Gear
Join Date: Feb 2005
Location: SW PA
Posts: 368
Default RE: Vaccum Power Door Locks 4000s

Look in the trunk, under the spare tire. The pump should be there. At least it is on the 5000 in the earlier years, '78 - '83.

'84 - '88, it's supposed to be under the rear seat, by the passenger side door.

If you find it, make it run and pull a hose off it, plug the barb, see if you have either vaccuum or pressure. If no, replace it and see if there is another hose, do the same. If it stops the pump in a short time, you have found the defective circuit, hoses, not wires. Apply relatively low pressure air into that hose, listen around the doorsills for leaks. Find them, patch them.

It's also possible to have a blown diode on the printed circuit board built into the pump base, actually, both. The pump will run forever but do nothing. I had one fail and an electronics tech fix it for me. He replaced diode, I re-installed, most of the trip home, till I stopped to unplug it, doors kept locking-unlocking. Took it back to him, he was surprised to find that the other diode had also blown, replaced that, worked well till I scrapped the car.

Another time, could not unlock the trunk, went to a service station, pulled up the carpet at the right rear door, popped a hose off the nylon tubing and applied their line pressure. Opened the trunk. When I got home, did as I suggest above, found the leak, spliced in new tubing, all was well.

Other models have a vaccuum tank, purged by manifold vaccuum. This shouldn't be on your system, as you say you hear the pump running. If you don't start the car, it would probably run till the battery died.



Old 11-01-2005, 09:50 PM
2nd Gear
Join Date: Mar 2004
Location: Swamplands of NJ
Posts: 761
Default RE: Vaccum Power Door Locks 4000s

If I remember correctly the pump on my 84 4000S was in the trunk on the right side somewhere near the wheel well.
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