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Vacuum Questions https://www.slantsix.org/forum/viewtopic.php?t=7338	Page 1 of 1

Author:	mszauner [ Fri Oct 24, 2003 4:19 pm ]
Post subject:	Vacuum Questions
I obtained every vacuum amplifier from every mopar in every junkyard and not a one of them seems to pass any vacuum. I finally bypassed the amplifier and run everything off the tree on the intake manifold. It seems to run everything fine but is that an OK thing to do? Any suggestions? Thanks. Mike

Author:	Craig [ Fri Oct 24, 2003 5:07 pm ]
Post subject:
Vacuum amplifier? You mean the one that operates the EGR valve? All that "amplifier" does is use the weak venturi vacuum port/signal to modulate/regulate the manifold vacuum that is applied to the EGR valve. It will not create "vacuum" out of nothing.

Author:	mszauner [ Sat Oct 25, 2003 1:26 pm ]
Post subject:	Yes
Actually, mine also was supposedly to run the vacuum actuators for the heat ducts too. It never was sufficinet to operate any of them, even when I ran the amplifier from the intake tree. So, once I hook all those lines directly from the tree, all works fine. The EGR opens when the temperature is correct and I get constant vacuum to the actuators. Will that cause any problems that way? Thanks. Mike

Author:	Charrlie_S [ Sat Oct 25, 2003 5:15 pm ]
Post subject:
The vacuum line that goes to the heater/AC control switch, should be connected directly to the vacuum tree on the manifold. Some cars have a vacuum resivour in the system. There should also be a one way check valve in the vacuum line.

Author:	mszauner [ Sat Oct 25, 2003 7:29 pm ]
Post subject:	How many valves
Should each line off the tree have a check valve? The brake booster line has one but the others don't. Thanks. Mike

Author:	Craig [ Sat Oct 25, 2003 10:45 pm ]
Post subject:
What exactly is this thing you are calling a "vacuum amplifier?" Is it actually a vacuum reservoir? Please describe it or post a picture. If it's a reservoir, it has a built in check valve and if you hook it up backwards it will not work. Yes, the brake booster has its own check valve for obvious reasons. Normally there is a check valve or two for the heater/AC stuff too. Often that is in a vacuum line under the dash, not in the engine compartment.

Author:	Charrlie_S [ Sun Oct 26, 2003 5:44 am ]
Post subject:
Craig is correct. The heater/AC check valve is usually under the dash, but sometimes they are missing. You can install it in the engine compartment. The only lines that need the check valve are, the heater/AC, and the brake booster. The purpose of the valve is to prevent loosing the vacuum from the componets, when engine vacuum decreases under heavy load. A symptom of this is, when accelerating, the air coming out the of the vents switches to defroster, or goes to hot, if it has a vacuum hot water valve. All this info can vary somewhat, depending on the year, make, model, and options.l

Author:	mszauner [ Sun Oct 26, 2003 11:19 am ]
Post subject:	Ok
I am definitely talking about a vacuum amplifier, not a reservoir, although one amplifier I obtained also has a reservoir. I did notice that when I alter the engine speed, I can hear the heater dampers opening and closing so I need to put a check valve in there somewhere in the line. BTW, I once tried posting a photo here but couldn't. I was told I needed to post a link to my website and put the photo there but I do not have a web site. However, I have since noticed photos being posted. Is there some change and I can now post photos? Thanks. Mike

Author:	DusterIdiot [ Mon Oct 27, 2003 11:34 am ]
Post subject:	1973-1976 Vaccuum 'Amplifier'
The start of the EGR cars in the 1973 model year added that nice black plastic item bolted to the top of the head, next to the choke heater relay. The label on it should be 'Vaccuum Amplifier'... it's just a storage/check system so vacuum routed from either the manifold (runner #6) or on some systems it can come from a carb port...then is run to the temp-vacuum switch on the radiator or thermostat housing, and over to the EGR. There are some other 'circuits' that can feed off this reservoir too, but all in all it is one of the single most notorious vaccuum leaks ever to crop up on our vehicles.... If you can find a way to make a no-leak work around you'll be ahead of the game, none of my cars have it attached anymore.... -D.Idiot

Author:	mszauner [ Tue Oct 28, 2003 1:31 pm ]
Post subject:	So..
Where can I get a vacuum check valve for use in the heater system? My routing of lines works fine except I notice the heater valves open and shut depending on RPM. Is there a specific vacuum pressure it should respond to? Thanks. Mike

Author:	Craig [ Tue Oct 28, 2003 8:01 pm ]
Post subject:
Hey mszauner, I still don't know what you are trying to do with a "vacuum amplifier". If you are referring to what I thinkyou are..... then it has NOTHING to do with your AC/heater mode doors. That comes directly off the intake manifold. What model and year car is this? AC? Heater only? This will help.

Author:	mszauner [ Wed Oct 29, 2003 5:51 am ]
Post subject:	Yes and No
It is a 73 Duster with heater and AC and when I got it the heater vacuum hoses were coming off the amplifier. That wonderful 3" diameter round black thing that say vacuum amplifier on it. Anyway, no vacuum ever came out of it even though it was fed from the manifold. I obtained several others from the junk yard and none of them worked either. So, I decided to hook all vacuum to the manifold tree. I now have the master cylinder booster, the heater/AC vacuum actuators, the line to the heat sensor in the air cleaner and the line to the heat valve that goes to the EGR all off the tree. Everything works fine except that variances in the RPM will affect the heater actuators and cause the dampers to open and close. I also noticed that the heat sensor in the air cleaner does not work properly. It will keep the air cleaner on cool air unless I plug the tip in the cleaner but then it will never resume cool air. Mike

Author:	Craig [ Wed Oct 29, 2003 7:07 pm ]
Post subject:	Vacuum solution (almost)
OK , now that I know what you have I was able to look in my 1973 Service Manual. I discovered that the EGR system and your vacuum amplifer has a hose connected from the vacuum amplifier to a "temperature control valve" on the fire wall right in the fresh air plenum. It appears you are confusing this hose as being connected to your AC system. I don't know just yet what this "temperature control valve" does but it has nothing to do with your AC system. I may be able to scan a few pages from the manual for you so you can see where all the hoses go. There should be a second hose feeding vacuum to your AC system and it is NOT connected to the vacuum amplifier.

Author:	mszauner [ Sat Nov 01, 2003 11:05 am ]
Post subject:	Where can I get a check valve
OK, Let me try one more time. when I got my car, it had a vacuum line running from the amplifier to the heater controls. I am not saying this is correct, I am merely saying the condition mine was in when I got it. Because nothing on the amplifier seemed to work, even after using multiple amplifiers, I decided the heck with it and took the amplifier off. I ran a line directly from the tree to the temperature valve in the head that controls vacuum to the EGR. It now works fine. I connected one line directly from the tree to the air cleaner heat sensor. It does not work well even though the heat sensor is new. I ran the other line from the tree to the heater controls. They work except you can hear them open and close depending on the RPM. I really only need the answer to two questions. First, is this OK to not have an amplifier and the concensus I see here is that it is fine. So I will leave that as is. My second question is where can I get a check valve for the line running to the heater controls since it obviously needs one. Thank you as always. Mike

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