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1991 420 SEL
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957 Posts
Discussion Starter · #1 ·
When I did a smoke test I had leaks coming out from my CO screw housing.
Is is normal?
I was reading on the Porsche forum that it is normal?
Vacuum leak at mixture adjustment screw - 83 911SC - Pelican Parts Forums

My top of the CO housing is broken a bit (I think they broke it so they can adjust it as it is not adjustable from factory, correct me if I am wrong).


can any expert in vacuum leaks chip in...

Thanks
 

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Outstanding Contributor
'17 GLS450, '14 GLK250 "Grandpa's Roadster" Project Car, 350SDL (Sold)
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Looks like someone butchered it getting the plug out. If it were still plugged, it wouldn't leak...
 

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1987 & 1991 C126
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John's correct..

I am sure some of us older guys remember a little plug covering the CO adjustment .back in the day'.. This one from a mid 1970s 140 Volvo..
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It would keep dirt from falling in and a small amount of unfiltered air entering the engine. Just replace when the CO adjustment was compleased.
I hadn't considered it to be a vacuum leak per-se, as it is located on the 'atmospheric' side of things.. [By that, I mean the air filter side of the throttle plate.]

One can replace that 'tower' if need be.
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1991 420 SEL
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Discussion Starter · #4 ·
Thanks John and MBL

I am aware that I can replace the housing. I would not want to if I do not have to (the old towers are riveted, the new ones are screws).
When you say someone removed the plug. can I just plug it ? do you have the part number for the plug in pic?
So I am guessing, it would be normal to leak if it is not plugged, correct?
My understanding is there is a spring loaded screw. Should that not have a good seal without the plug?
Thanks for your time...
 

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On the surface of things, I doubt the Volvo part I cited would work for our MB systems.

The earlier systems looked a bit different than what we have.
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'17 GLS450, '14 GLK250 "Grandpa's Roadster" Project Car, 350SDL (Sold)
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My understanding is there is a spring loaded screw.
Not sure what you mean. The screw at the bottom of the hole is the adjustment screw. It doesn't seal anything. The "Volvo" part might work, but I suspect it sticks up too far. Anything you can fit in the hole that you can later remove should do the trick. I was thinking a part from a fluid line plug set might work.

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1999 500SL, 1988 SEC
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Those are not rivets holding the tower in they just look like it. Take a small chisel to the side of the screw flange and tap the chisel with a hammer. It will start to unscrew. Its one of those German anal things
 

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1991 420 SEL
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Discussion Starter · #9 ·
Those are not rivets holding the tower in they just look like it. Take a small chisel to the side of the screw flange and tap the chisel with a hammer. It will start to unscrew. Its one of those German anal things
Can this be done with the housing in place or the fuel distributor has to come off?
 

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Yes, he's right.. Once you get 'em loosened they should back right out. There is no thread lock there.

As shown, the adjustment screw kit does come with new bolts, gasket etc...
They are the so called 'break away' design.
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