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1986
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9 Posts
Discussion Starter #1
I am new to both Cadillac and this forum so I will apologise in advance for my ignorance.
I just inherieted a 1986 DeVille / Fleetwood and im doing some trouble shooting.

is it normal when you turn the key 1/2 way, to have the vacuum pump (under the battery) constantly running?

what is this pump for anyway?
thanks!
 

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Registered
1986
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9 Posts
Discussion Starter #3
im not sure what its called, I do know its under the battery area (front left corner) when you peek under the car you can see it and feel it humming. the only way to turn it off is to pull the fuse labled "vacuum pump"

if it is the leveler pump like you say, is that for some air suspension or something?
if it is for that and its constantly on, does this mean one of the suspension air bags has a leak?
wouldnt I see this in the cars stance? the car seems level all around and seems to drive ok.

thanks
 

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1985 Sedan DeVille
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1,883 Posts
The thing under the front left wheel skirt is the vaccum pump, and it runs whenever the key is the ON position. Basically, engines typically put out between 15-20 hg inches of vacuum which is used to drive a variety of systems (EGR solenoid, power brake booster, climate controls, cruise control, ...). The 4.1 engines don't put out that much, so they added the vacuum pump as a secondary booster. It's part of the main vacuum harness. If the engine is running really well and you feel confident with the brakes at lower vacuum you can disable it at the fuse box. I have been looking at some aftermarket hot-rodder vacuum pumps that have built-in pressure switches for my '85, but I haven't had that money to waste yet.

The electronic leveling control is completely unrelated system. There is a sensor under the rear seat that periodically checks to see if it's level, and then commands an air compressor behind the battery to engage if the rear is sagging or off kilter. That pump only runs when it's commanded.
 

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1986
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9 Posts
Discussion Starter #5
mystery solved!
I guess i'll plug the fuse back in if thats the way its meant to be.

thank you for solving my delema.
 
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