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Old 05-07-2011, 10:25 AM
ivandrocco's Avatar
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vacuum lines - 300cd

Trying to figure out what is up with my vacuum lines- i've read the stickies and searched but some aspects aren't clear.

Attached is Samuel Ross's photo with the text and arrows. The other photos are my mess.

Some of this might be coupe specific? Let's start with what I know.

Two main lines draw off the vacuum line to the brake booster. The first attaches to a three way connector, one direction going to the egr/vac switch on top of the valve cover, the other to a second three way connector that connects to the green valve and a line to the transmission. I eliminated the switch on top of the valve cover and replaced the double 3-way connector system with a single three way connector.

The other line from the restricted orifice closer to the brake booster supplies the accessories via a 4-way connector. This was a mess when I got the car.

-3-way check valve splits vacuum between yellow line w/ grey stripe (reservoir) and a plain yellow line (door locks).

-Second yellow valve connects to blue vac line (seat backs).

-Green vac line (climate control)

-Brown vac line (ignition/shutoff)

In addition to these lines, there is a brown vac line w/ blue stripe that goes down to the IP? and a black vac line that connects under the green valve.

---------------------------------------

In Samuel Ross's image, the yellow three way valve is connected to a three way connector that supplies the reservoir and door locks, with the other orifice connecting a black vac line for the cruise control. My lines didn't come set up this wa

I want to isolate all of the accessories. Does that mean I can just leave everything disconnected and unplugged except for the brown vac line? Are the brown w/blue stripe and black lines routed correctly?

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vacuum lines - 300cd-w123vacdoorlockdiag.jpg   vacuum lines - 300cd-dsc05609.jpg   vacuum lines - 300cd-dsc05610.jpg  
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Old 05-07-2011, 11:36 AM
Yak Yak is offline
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I built a custom set of drawings for the coupes. Search for "definitive" by Yak. It's got all the parts for a Federal '83 coupe with pics of the engine bay and drawings from various manuals.

The yellow "three way valves" are check valves. That means they let the pump draw vacuum from one side, but they then hold that vacuum when the pump is stopped. They "share" vacuum on the other side as long as the reservoir has vacuum so you can lock/unlock the doors.

My '83 had a 5 way connector off the second line: 1 = in/source; 2 = out/doors (checkvalve); 3 = out/brown shutdown; 4 = out/seats (checkvalve); 5 = out/A/C.

What problem are you trying to solve?
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Old 05-07-2011, 11:46 AM
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Trying to fix my lack of understanding...

So why can't you throw one of the check valves on the line to the climate system in order to utilize it without compromising the entire vacuum system with leaks?
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Old 05-07-2011, 11:54 AM
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yak, these diagrams are awesome! can't believe i haven't seen this thread yet.
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Old 05-07-2011, 12:20 PM
Yak Yak is offline
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Quote:
Originally Posted by ivandrocco View Post
Trying to fix my lack of understanding...

So why can't you throw one of the check valves on the line to the climate system in order to utilize it without compromising the entire vacuum system with leaks?
Key to understanding vacuum is that it's not some magical thing. It's really just an area of low pressure. Air tries to flow from high pressure to low pressure. Vacuum doesn't "leak out", air leaks in or you're unable to establish a low pressure area.

You could put a check valve on the A/C system, but what would happen? The pump would establish a low pressure area on the "supply side" of the vacuum and the check valve would stay open - like it's supposed to in an "operating" system. The leak on the demand side would have the high pressure leaky air flowing into the low pressure pump so your system can't attain and maintain proper vacuum level (like it's not supposed to). So the check valve won't "protect" the vacuum level elsewhere.

The door lock reservoir checkvalve assumes a non-leaky system and holds the low pressure until you turn the key and let small bursts of higher pressure into the system. Lock and unlock a few times (or have leaky components) and the pressures equalize. The coupe seats are a one-shot deal.

A big hint if your seat backs are intact: can you see the locks rotate over, or do you get a screechy noise as the actuator compresses the spring? These are actually easy to check with a hand Mity-Vac. Pull the blue line under the seat, pull some vacuum and see if it holds. Don't forget there's a relay behind the glovebox. It's normally closed but is electrically opened by the door switches, so unless you've got a short in the door switches it'll be okay.

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