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1984 380SL
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9 Posts
plugged hose

Hi guys, I'm new to the forum and working through some issues on my '84 380sl. Many of you have already been a huge help on other things so thanks for that. I'm pretty sure I have a vacuum leak: whistling at ~1500rpm, very occasional rough idle/misfire at operating temp on a warm day. The whistling seems to be coming from the area of the IAC valve, but I haven't smoked it out or propaned it yet (that will be interesting and/or terrifying). It seems a vacuum hose is disconnected from the front of the warm up regulator, with a hose nearby plugged with a screw--I'm assuming that's the disconnected one. According to diagrams that front tube runs to the intake manifold. Any idea why this would have been plugged/disconnected? The plugging the WUR hole with my finger doesn't affect the whistle. Aside from the misfire the other weird thing it's doing related to idle is a ~5 second noise during the transition from cold idle to warm idle. When I first heard it, it sounded like a high frequency spark/arc kind of sound or maybe clicking, but it's definitely coming from the front, I'm guessing from the IAC valve based on youtube/forum searches. I'm going to try to clean it out soon and see if the vacuum connections are intact. Could a leak cause the valve to make that noise? Would ambient temperature affect the rate of leak so much to cause the misfire/hesitation? All related? Thanks so much for your help.
 

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2007 CL600, 2003 SL55AMG, 1987 560SEL ECE, 1985 280SL
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1,513 Posts
Not sure why the vacuum line is plugged, but it shouldn't be. I would restore to spec and check for leaks with carb cleaner or propane. Do it on a cold engine, and you're safe.

You will not get your engine to run smooth with vacuum leaks...

The 5 sec sound is probably the A.I.R pump aka smog pump that kicks in. It gets air from the air filter through a rubber hose going out on the RHS of the filter and down. The hose has a plastic connection which can leak and give false air, which you will hear.
 

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1985 500SL + 2009 GLK (previous 250, 280SL, 230TE, 430 ML)
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1,032 Posts
Attached is a diagram for my 1985. The warm-up regulator on K Jetronic Euro versions adjusts the mixture after start up, the duration is based on initial (ambient) temperature. A heated bimetalic lever adjusts the mixture.

A secondary function uses the vacuum to enrich the mixture during full throttle or for accelaration enrichment. A differential membrane in the WUR uses vacuum to sense partial load accelleration.

There is also a vacuum line to the top of the WUR from the ISC, I have no idea what it is for.

Whilst trouble shooting a central locking problem, I found that one vacuum hose to the intake plenum was disconnected, imposible to see, but connected a gauge to the other of the line using a T-joint and measured no vacuum.
 

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vacuum door lock fix

Thought I would through out my fix to possibly help diagnose lock problem. I removed driver master lock and checked for vacuum with vac pump found the lock (red/Yellow) and unlock (green/yellow) were not holding vacuum, I then lit up my trusty cigar and blew smoke into each line, smoke began coming from passenger door on one and drivers door on the other. Replaced both lines that had broken in hinge area by removing lower dash and feeding new line down along old one. push button for door light can be removed to help feed line into door. Not easy but definitely doable, took me about 4 hours to run new lines. LOCKS WORK!
 

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1974 450SL, previously 1986 420SEL
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180 Posts
Thought I would through out my fix to possibly help diagnose lock problem. I removed driver master lock and checked for vacuum with vac pump found the lock (red/Yellow) and unlock (green/yellow) were not holding vacuum, I then lit up my trusty cigar and blew smoke into each line, smoke began coming from passenger door on one and drivers door on the other. Replaced both lines that had broken in hinge area by removing lower dash and feeding new line down along old one. push button for door light can be removed to help feed line into door. Not easy but definitely doable, took me about 4 hours to run new lines. LOCKS WORK!
What did you use for replacement vacuum line in the doors?
 

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The original line is no longer available,I purchased 1x4 mm 15' line on ebay for 14.99. You can just search 450sl vacuum line and several will come up. It takes about 5' to run each line from door actuator to under dash where I used a slightly larger rubber line purchased at auto zone to splice into original line under the dash and zip tied onto the new line that is just slightly smaller.I found green and red zip ties to match original line color.The new line comes in clear so I used a sharpie to mark a black line down one so I could tell the difference when I got under the dash.(the zip ties are important I tried locks without them and it didn't fit tight enough to hold vacuum).Good Luck
 

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1974 450SL, previously 1986 420SEL
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180 Posts
For an early (1974) 107, where is the "switchover valve" for the engine vacuum retard (#9 in Graham's first diagram in Post #6 )? (I found a vacuum line from the throttle body disconnected and something that looks like the switchover valve attached to the coolant reservoir, with a vacuum line running to the distributor. Is that it?
 

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1981 280SL AT
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275 Posts
Looked through this thread a couple times and I did not find a vacuum diagram for the 1981 280SL, such as the one I own, and wondered if I missed something or does it not exist? Saw Nobby's for the 1977 that is "found in the 280SL" but it does not show some of the components I have, for instance the vacuum storage thing under the right front fender. Any help would be appreciated.
 

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Mercedes 450 SL 1973
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1 Posts
Does any of you have the pics from this post?

I posted the diagrams for the early 107 engine, door locks and heating system in the other thread. Question - Is there a way to upload the pictures to benzworld - my web space is getting kind of full!

Here they are again. Maybe someone with a manual could add the later models. I am trying to get ready for a trip South!

Engine vacuum retard:


Heater Vacuum controls:




Door Lock vacuum systems (several models)


No pictures in this one.
Can someone repost them or are they already in the thread?
//Nick
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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9,927 Posts
Wrong Section of EGV107?

This thread on vacuum systems is listed in Section 47 of EGV107. Section 47 is for Fuel Delivery Systems. Thread doesn't seem to be right Section.

Same for thread : "Vacuum advance vacuum hose WTF!!!!"

Chassis vacuum systems are in section 83 of my paper manuals. Section 14 includes engine vacuum systems.
 
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