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  #31  
Old 01-30-2007, 10:20 PM
angst's Avatar
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Location: Chattanooga TN
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Quote:
Either the valve is bad or the rubber cap that secures the line is bad.
I discovered that the "modulator valve" cap was in crummy shape. I hadn't given this any attention before. I went on a old thread archive search blitzkrieg.
Should I stay way away from any adjustment on the modulator, or will turning a notch clockwise buy me more time for a part that may be on its way out?

I dont quite understand your tips in your last post regarding testing under 'no vacuum' conditions. I tried doing a straight through connection of the lines that T down to the vacuum control valve and covered the T above the damper with my fingers and the engine would not shut off on its own.

Im encouraged by finding the cracked modulator cap. Perhaps a fresh cap and a damper from the local stealership and I may be able to shut off without popping the hood.

I could not find the vacuum control valve at fastlane. Does it go by other names?
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  #32  
Old 01-30-2007, 10:30 PM
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Quote:
Originally Posted by angst View Post
I dont quite understand your tips in your last post regarding testing under 'no vacuum' conditions. I tried doing a straight through connection of the lines that T down to the vacuum control valve and covered the T above the damper with my fingers and the engine would not shut off on its own.
I'd like to isolate the VCV and the modulator from the vacuum system. Therefore, please plug the supply line as directed above and drive the vehicle. If the vacuum problem is eliminated and you maintain brakes, then the VCV might be considered the culprit. If the brakes are lost and the engine still won't shutdown, then you've got more problems than the modulator and the VCV.

Quote:
Originally Posted by angst View Post
I could not find the vacuum control valve at fastlane. Does it go by other names?
Here's the valve.........a bit costly, however.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1XL0VHEI02071C4AAG&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1984&product=D2032-15990&application=000004527
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  #33  
Old 01-30-2007, 11:23 PM
ChicagoJones's Avatar
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What happens if you bypass the VCV? The reason I am asking is because I think I may have a vacuum leak somewhere. I am registering only 4.4-5 hg with the VCV and the transmission is shifting hard. Directly hooked up to the vacuum pump I am getting about 24 hg. With VCV bypassed and a direct shot to the trans modulator I am registering about 9 hg. It shifts very nicely now. I think I want to keep it this way until I figure out what is leaking. Would it hurt anything?
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  #34  
Old 02-01-2007, 07:19 PM
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Looks like intermittent shut off prob is solved for now. I was checking some vac measurements again. On the the valve up by the brake booster I disconnected different lines and measured vac. Both nipples before the white valve measured about 12-15hg.
There are two nipples on that white valve. One goes to the VCV and modulator, and the other goes to lines going back into the cabin.
I stumbled onto that when I switched the lines on the two nipples that it would turn off on demand consistantly and instantly instead of only turning off 40% of the time.
Why this works I don't know cuz both holes have the same amount of vacuum measured at idle. They also have the same amount of vacuum if you pull the lines first, start it, turn ignition off, and measure with ignition off and engine running.

Trans shifts seem reasonable. I am getting a measurement of 15hg on the main line coming off the pump. Is this adequate? Some step by step guides say 15-20, others say to troubleshoot the pump if you are not getting 21+ here.
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38K miles on flatplate heat exchanger and various diesel/veg blends. prior to that 4K miles on unheated veggie blends with kero and DinoD.
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  #35  
Old 02-06-2007, 08:27 PM
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transmission shift issue resolved

I had been chasing a transmission shifting issue that I finally fixed today The condition was a firm 1-2, soft 2-3, and slightly firm 3-4. After reviewing many posts, as I am a MB Newbie, I replaced the old and brittle vacuum lines. Unfortunately, only a slight improvement...basically the same firm 1-2, soft 2-3, and slightly firm 3-4. Next, I adjusted the Modulator and Bowden cable. The adjustments again improved the soft 2-3...but I was unable to improve the firm 1-2. It was a compromise. I stumbled across another post that recommended replacing the plastic valve levers as they wear to the point that the valve is not functioning properly. I removed the plastic black box on the valve cover and sure enough they were shot. I had seen a DIY on DieselGiant.com so I ordered the plastic valve levers and replaced today. I wish I checked the valve levers first as the Bowden cable and Modulator adjustments were not necessary. However, I am very happy now, the transmission is shifting like new!

http://www.dieselgiant.com/trannyleverreplace.htm

Quote:
Originally Posted by angst View Post
Looks like intermittent shut off prob is solved for now. I was checking some vac measurements again. On the the valve up by the brake booster I disconnected different lines and measured vac. Both nipples before the white valve measured about 12-15hg.
There are two nipples on that white valve. One goes to the VCV and modulator, and the other goes to lines going back into the cabin.
I stumbled onto that when I switched the lines on the two nipples that it would turn off on demand consistantly and instantly instead of only turning off 40% of the time.
Why this works I don't know cuz both holes have the same amount of vacuum measured at idle. They also have the same amount of vacuum if you pull the lines first, start it, turn ignition off, and measure with ignition off and engine running.

Trans shifts seem reasonable. I am getting a measurement of 15hg on the main line coming off the pump. Is this adequate? Some step by step guides say 15-20, others say to troubleshoot the pump if you are not getting 21+ here.
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  #36  
Old 05-18-2007, 02:32 AM
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Reading this thread i'm interested in whether the Valve Box is the same on the 616? Just as unneccesary?
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  #37  
Old 05-18-2007, 03:05 AM
ForcedInduction
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Quote:
Originally Posted by ThosDoran View Post
Reading this thread i'm interested in whether the Valve Box is the same on the 616? Just as unneccesary?
Yes.
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  #38  
Old 05-18-2007, 04:57 PM
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EGR removal and shifting 1982/300sd

Hello list,

Brian Carlton made a statement here as follows............. On all SD's from '81-'85, the two vacuum switches on the top of the valve cover serve to operate the EGR exclusively.

They have no direct operation or effect on the transmission shifting.

I've recommended to everyone who has these engines to remove all the Tecalan lines that lead to and from the black box.

One line is the supply vacuum.........one line is the vent.........and the third line leads to the thermo vacuum valve in the thermostat housing and then onto the EGR valve.

These switches frequently leak and have an undesirable effect on transmission shifting however, they have no direct function reagarding control of transmission vacuum.

Well when I short out my black box, two Tecalan leads, in and out, shorted with a tube!
The 1st gear on down shift, gives a big clunk
I already have the EGR plugged!

I have just got my tranmsssion working quite well now, changes up through all the gears nicely

Any thoughts on this appreciated.

Brian
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  #39  
Old 05-18-2007, 05:40 PM
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Location: Blue Point, NY
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Quote:
Originally Posted by gavinbr View Post

Well when I short out my black box, two Tecalan leads, in and out, shorted with a tube!
Whatever possessed you to go and do that??
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