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  #1  
Old 07-01-2001, 12:42 AM
Brrrrs
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My locks work when they want to. When locked, ( after a few hours), they will not unlock. When the engine is running, they work fine, although sometimes, the engine will not shut off. Any ideas where to look first? DB

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  #2  
Old 07-01-2001, 05:01 AM
Jax,FL Chris
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300D vacuum leak

I had a similar problem with my 78 300D.
The car would not shut of but if you closed the door and locked it, the engine would slowely cut off.
My problem was a leaking trunk lock diaphragm.
On my 300D there is an access panel on the back trunk wall beside the lock. With this removed you should be able to see the diaphragm.
This is only my experience, your leak could be anywhere but this is an easy place to look before trying to test vacuum lines.
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  #3  
Old 07-01-2001, 09:40 AM
Brrrrs
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I have replaced a trunk diaphram, as well as door diaphrams in the past. I guess I dont want to face the inevitable, that i have to start dissassembling the car and find the culprit. Thanks anyway. Anyone else? And by the way, what made you start with the trunk diaphram?
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  #4  
Old 07-01-2001, 12:21 PM
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Join Date: May 2001
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Are you using a hand held vacuum pump with a vacuum gauge? There about $35-40 at the local parts store and worth every dime when tracking a vacuum problem.

Did you check the fuel door lock? I sold a 77 450SLC that had vacuum everything including seat back locks. My fuel door lock was the problem.
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  #5  
Old 07-01-2001, 04:26 PM
Jax,FL Chris
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Vacuum leak on 300D

I had a feeling that my problem was the trunk lock diaphragm as that was the first lock to cease working.
The other doors would unlock/lock but the trunk would stay in the locked position.
My first vacuum problem was with a 3 way valve under the hood that went to the cruise control.
I did not have a vacuum pump so I unplugged a line and bypassed it until I located the leak. The leak was in the 3 way valve going to the cruise control.
Good luck,
Chris
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  #6  
Old 07-03-2001, 10:36 AM
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Isolate your problem

Greetings,

In order to track down your vac leak, you're gonna need a mighty vac or similar vacuum producing tool. I started under the hood where the vac comes off the power brake booster. There should be several lines coming off from there. IE, one for shut down vac only, one for door locks, one going to climate control. I pulled a vacuum off of each seperately to see which one leaked down to resolve my problem. The tricky one is the shut off vac switch located on the key start. It is a two way valve that releases pressure so you can start up the car, but it then goes to a vac lock situation in the running mode without pulling a vac on the shutoff valve. This little valve can and will leak causing your system to bleed off vacuum while the engine is running, thus keeping your air reservoir from storing a vac for operation of the door locks with the engine turned off.

Good Luck,

Charles
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  #7  
Old 07-03-2001, 10:29 PM
Brrrrs
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What is a mighty vac? I have a hand vac pump and a A/C Vacuum pump.
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  #8  
Old 07-03-2001, 10:58 PM
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Mighty Vac

Greetings,


A mighty vac is the name of a vacuum tester sold by most part places. It allows you to draw a vacuum on individual components to isolate a vac leak in your system. If you already have such a device, then disregard.


Charles
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  #9  
Old 07-05-2001, 11:31 AM
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Can-do, is my ign. vaccuum switch bad?

I also am having vacuum leak problems. I fixed one last evening and I think there may be another source. With a hand vacuum pump with gage 'Teed' into the main vacuum source in the power brake booster area, I get a vacuum reading of 5 inches with the engine idling. (The fuel shutoff works at a minimum of 4 inches, so this is barely enough). With the engine running at 5 inches vacuum, when I pinch the rubber connector going to the brown line, the vacuum rises to at least 10 inches. Pinching the other colored lines (green-CLIMATE C; yellow-LOCKS; yellow/black-RESERVOIR)does not change the vacuum value.

My question is, should the brown line be contributing to that much of a vacuum loss, or is this a sign that the ignition vacuum switch has gone bad?


Gary

'79 300D
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  #10  
Old 07-06-2001, 12:11 AM
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Vac Leak, ain't this fun

Greetings Gary,

If your engine vac system is set up like mine, and from what you say, it probably is. The brown line goes to your key switch vacuum valve, and off that valve comes a brown with blue stripe going to your Injection pump shutoff valve. This valve bleeds off the air in the brown / blue line when the key is turned in the start position and then reverts to a vacuum on the solid brown line. The easiest way to test out this switch is to pull the brown line off the tee under the hood and pull a vacuum with a hand pump at that tee without the brown line being involved at all.It's gonna take some pumping to draw a vacuum because you are also drawing down your vac storage reservoir. If the locks all go down when you depress the door knob, and continues to hold a vacuum, minus about 4-10 psi for the door lock actuation that is, the rest of you system is leak free. Then put your hand vac on the brown line and pull a vacuum and see if it holds, then turn the key to the start position, and pull another vac on that same line. If it bleeds off the start vac valve is leaking air all the time in the run mode, it should be drawing a vacuum. It is only held in place by two screws on the ignition switch itself, so removal is pretty easy if you remove the kick panel and have small hands to get to the back screw blindly. I cleaned mine out with wd-40 to get rid of the gunk holding the o-rings, then sprayed a little silicon into it to lube the rubber seals contained within. So far it's been doing great, but as a back up I ordered another valve just in case this one fails me again. They're cheap, some $16.00

Any other help I can provide, just let me know.


Charles

P.S. All testing is done with the engine off.

[Edited by can-do on 07-06-2001 at 12:23 AM]
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  #11  
Old 07-11-2001, 12:58 PM
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Thanks for the info, Charles.

I tested the vacuum on the brown line circuit and found that there was a small leak when the key was in the "ON" position. I replaced the vacuum switch with a new one and it now holds a vacuum at "ON" and "OFF", and bleeds off the vacuum in the "in-between" key position. I noticed that the new switch had a blue mark on one of the tubing connections. I connected this to the brown/blue stripe line that goes to the IP. I noticed that the old switch was connected with the line colours interchanged. I don't know if this makes a difference, but everything is working OK for now.

I get a vacuum of 11 inches Hg throughout the system now which is probably a drop in atmospheric pressure of about 5 psi.

Gary
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  #12  
Old 07-11-2001, 10:17 PM
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Glad to hear your car sucks again

Greetings Gary,

If you have replaced the valve then you won't find anymore problems concerning that area for a leak. Even if they had the valve lines switched it should still hold a vac with the solid brown line when off and either one while it was running.

Charles
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  #13  
Old 07-16-2001, 02:55 PM
jeric
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How long?

GREAT THREAD.

I've just completed dianostics on my vacuum lines. My ignition vac valve is bad. Is there an easy approach to this task? ie; remove the cluster panel? or, are the screws as such that they can easily removed/replaced, blindly?

Then, assuming that all related vacuum connections are say 100% viable how long should the lock/unlock functionality of the door locks last? Currently, mine last for about 5 hours, then they will no longer unlock.

Thanks for all the help
jeric
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  #14  
Old 07-16-2001, 05:08 PM
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Do it the easy way

Greetings Jeric,

Don't remove the cluster to get to the vac switch, remove the kick panel instead because the valve is located on the side of the ignition switch and easiest to get to with kick panel removed. It will simply be a very small valve with two lines going to it. Two screws holds this jewel in place and the top screw is the most difficult to remove and replace. If you own a small offset screwdriver, this is the best approach on the top screw. Insure you test the valve properly before considering it dead. Also, there is a chance that dirt has gotten into it and has caused the o-rings to leak, so spaying wd-40 into the vacuum line ports and working the valve button a few times generally frees up the dirt, followed by a squirt of litium lube might fix your problem as well. Mine is still doing fine after a clean out and relube.

Charles
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  #15  
Old 07-17-2001, 09:19 AM
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Jeric,

As Charles said, make sure that the switch is defective first.

I replaced mine by popping out the cluster just enough so I could see the switch. It was easiest to remove the screws by accessing them from underneath with the kick panel removed. If your arms and hands are small enough, you might get at the switch with your left arm (to some degree) from above and with your right arm (short screwdriver) from underneath.

Gary

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