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1992 Fleetwood S&S Hearse, 1993 Buick Roadmaster
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Discussion Starter #1
1992 Cadillac Fleetwood 4.9. Was changing my oil and saw a part, just forward of the front drivers-side tire. Whatever it is, it's disconnected.

What is this part?



By the way, I'm talking about the assembly with the long hose coming off of it, and the tiny hose sticking out that looks like it might be to let out water or air. I don't remember seeing this on any other car I've owned. Maybe it just looked different?
 

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85 Coupe Deville 4.1 V8 & 4.3 V6 Deisel & 1970 Eldorado
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Looks like the electric vacuum pump as used on my 85 Deville. I thought they stopped using these when they went to the 4.5. The 4.1 engine did not generate enough vacuum to run the accessories and brake power booster so cadillac used an electric pump instead.
 

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1992 Fleetwood S&S Hearse, 1993 Buick Roadmaster
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Discussion Starter #3
Looks like the electric vacuum pump as used on my 85 Deville. I thought they stopped using these when they went to the 4.5. The 4.1 engine did not generate enough vacuum to run the accessories and brake power booster so cadillac used an electric pump instead.
I looked it up on Google based on what you said, and it is an elctric vacuum pump for sure. But why is it there? Also, it's disconnected. From older posts I found, it looks like it is mostly used to boost vacuum for the brake system. This car doesn't have the most impressive brakes I've ever used, but they seem suitable.

Any idea why the pump may have been disconnected? Should I reconnect it? Any advice appreciated!
 

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1992 DeVille
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ratmonster said:
I looked it up on Google based on what you said, and it is an elctric vacuum pump for sure. But why is it there? Also, it's disconnected. From older posts I found, it looks like it is mostly used to boost vacuum for the brake system. This car doesn't have the most impressive brakes I've ever used, but they seem suitable. Any idea why the pump may have been disconnected? Should I reconnect it? Any advice appreciated!
I'd probably reconnect it. If you spray the open hoses slash ports with throttle cleaner (with the engine running) do the rpms jump up a bit?

If it's unplugged theoretically you should have a vacuum leak. And you'd wanna fix that. At least cap all the open ends till you figure it out. but the best thing would be plug it all back in.
 

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1992 Fleetwood S&S Hearse, 1993 Buick Roadmaster
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Discussion Starter #5
I will reconnect it tomorrow and see what changes, if anything. Whatever it is, I sure didn't know I was missing it!
 

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1985 Sedan DeVille
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I looked it up on Google based on what you said, and it is an elctric vacuum pump for sure. But why is it there? Also, it's disconnected. From older posts I found, it looks like it is mostly used to boost vacuum for the brake system. This car doesn't have the most impressive brakes I've ever used, but they seem suitable.
Vacuum pressure is used for a bunch of accessories, not just brakes but also things like vent selection in the dashboard (diaphragm controlled vents), cruise control, etc. Engine vacuum varies under load quite a bit (open throttle going uphill = low vaccum, AC switches from vent to defrost, brakes don't have any feel at the top, etc), and the pump provides a steady supply and ensures the accessories work smoothly under all conditions. The car will work fine without the pump, but it works like a Cadillac with the pump.

Having said that, I was also under the impression they stopped using it with the later models.

Any idea why the pump may have been disconnected? Should I reconnect it? Any advice appreciated!
They are noisy, they drain power when running, and if they leak they will run on and on forever. I used to pull the fuse on mine sometimes, and I deleted it completely when I did the 4.9 swap into my 85. They aren't necessary, just make stuff work better, at the cost of noise and potential power drain.
 

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1992 DeVille
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ehall said:
Vacuum pressure is used for a bunch of accessories, not just brakes but also things like vent selection in the dashboard (diaphragm controlled vents), cruise control, etc. Engine vacuum varies under load quite a bit (open throttle going uphill = low vaccum, AC switches from vent to defrost, brakes don't have any feel at the top, etc), and the pump provides a steady supply and ensures the accessories work smoothly under all conditions. The car will work fine without the pump, but it works like a Cadillac with the pump. Having said that, I was also under the impression they stopped using it with the later models. They are noisy, they drain power when running, and if they leak they will run on and on forever. I used to pull the fuse on mine sometimes, and I deleted it completely when I did the 4.9 swap into my 85. They aren't necessary, just make stuff work better, at the cost of noise and potential power drain.

What kind of noise??

I too was under the impression it was eliminated as well. I'll study up in my FSM when I have time and post some text if I find some
 

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1985 Sedan DeVille
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Mine made a buzzing noise whenever it was running, like a quieter version of the suspension pump, but nearly constant. Also runs whenever key is in the ON position, not just when engine is running.
 

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1992 Fleetwood S&S Hearse, 1993 Buick Roadmaster
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Discussion Starter #9
I hooked it up, and it is deffinitely loud! Looking at it today, it appears that a vacuum line (barely seen in the picture, just a stub that disappears behind the conrtol arm) connects to a metal line, which connects to another vacuum line, and connects to the brake booster. Makes sense.

There is a long hose visible in the picture. I cannot find anything to hook it up to! Everything else seems to be complete - no lines just hanging around taking up space, no lines capped off that I can find. Having it hooked up and running had no effect on how the car drove or stopped - but that makes sense, especially with that long hose not connected. I am still very confused.
 

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1992 DeVille
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Look in the radius that the hose stretches for open ports. I did the same thing on my friends car and was able to find the port.

You have your fsm yet?
 

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1992 Fleetwood S&S Hearse, 1993 Buick Roadmaster
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Discussion Starter #11
Look in the radius that the hose stretches for open ports. I did the same thing on my friends car and was able to find the port.

You have your fsm yet?
No, not yet. Requires some green foldy stuff... haven't seen the stuff in so long that I don't remember the name.

I tried your same technique and couldn't find anything. I looked at pics of a different type of vacumm pump, and it had a hose that connected back to iteself. Any chance that could be it?

I guess you don't have this stinker on your Cadillac, dchavezo?

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Vacuum pressure is used for a bunch of accessories, not just brakes but also things like vent selection in the dashboard (diaphragm controlled vents), cruise control, etc. Engine vacuum varies under load quite a bit (open throttle going uphill = low vaccum, AC switches from vent to defrost, brakes don't have any feel at the top, etc), and the pump provides a steady supply and ensures the accessories work smoothly under all conditions. The car will work fine without the pump, but it works like a Cadillac with the pump.
Any chance you can show me where yours hooks up?
 

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1992 DeVille
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ratmonster said:
No, not yet. Requires some green foldy stuff... haven't seen the stuff in so long that I don't remember the name. I tried your same technique and couldn't find anything. I looked at pics of a different type of vacumm pump, and it had a hose that connected back to iteself. Any chance that could be it? I guess you don't have this stinker on your Cadillac, dchavezo? ---------- Any chance you can show me where yours hooks up?
I don't think I do...I've never seen it and my FSM doesn't mention it in the vacuum diagram.

Here's a pic from dennis93coupes (i think it was his) photobucket.




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Maybe yours is special because of *insert a clever joke about hearse/heaven and needing a vacuum pump to get there*
 

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1992 Fleetwood S&S Hearse, 1993 Buick Roadmaster
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Discussion Starter #15
So.... According to the middle picture -

"Vacuum pump exhaust hose (vented to atmosphere)"

So the hose connects to NOTHING!!! Well, that was a big to-do about nothing... makes me feel a tiny bit silly.

However, knowledge is power, so now, I'M INVINCIBLE!!!

Thanks for all the help guys! And thanks dchavezo especially for posting the pages from the book!!!
 

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1992 DeVille
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ratmonster said:
So.... According to the middle picture - "Vacuum pump exhaust hose (vented to atmosphere)" So the hose connects to NOTHING!!! Well, that was a big to-do about nothing... makes me feel a tiny bit silly. However, knowledge is power, so now, I'M INVINCIBLE!!! Thanks for all the help guys! And thanks dchavezo especially for posting the pages from the book!!!
Of course rat! It's good to have this stuff online for people who don't have the FSM. I lucked out and got mine for 20 bucks on eBay =P

I suppose the theory behind the vent is similar to the EGR solenoid vent/filtered port.

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Also that's my favorite fix: when you don't have to do anything =D
 

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1992 Fleetwood S&S Hearse, 1993 Buick Roadmaster
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Discussion Starter #17
Well, just as an update, I've driven around with it plugged in (and it runs constantly, which is a little annoying) and the only difference I can tell is it seems like I have slightly more brake. I'm going to leave it plugged in, because it was built to be used. The radio covers up most of the noise it makes, so... meh.
 
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