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Registered
1991 560 SEC
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21 Posts
Discussion Starter #1
I need to do a vacuum test. Where do I connect the smoke to the engine?
thanks
 

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90 420SEL, 00 BMW X5, 00 Lexus RX300, 01 Chrysler Town and Country
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377 Posts
Normally, the smoke machine is connected to the Brake Booster line. Are you using a commercial smoke machine?
 

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Registered
1991 560sec. 1991 560sel 1969 280SL
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1,333 Posts
i don’t bother with disconnecting the brake booster line, there is a chance it might crack/ damage the plastic. I just hook up at the nipple that supplies vacuum to the EZL. Works great!
Do not forget to seal off the air intake at the metering plate.
 

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Moderator
1991 500SEC 55K mi. 1987 560SEC Now 153K mi. 2020
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4,778 Posts
i don’t bother with disconnecting the brake booster line, there is a chance it might crack/ damage the plastic. I just hook up at the nipple that supplies vacuum to the EZL. Works great!
Do not forget to seal off the air intake at the metering plate.
Having toasted/replaced a brake booster vac line here, I totally embrace the EZL method.

m
 

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SuperModerator
1986/1990 W126
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14,481 Posts
i don’t bother with disconnecting the brake booster line, there is a chance it might crack/ damage the plastic. I just hook up at the nipple that supplies vacuum to the EZL. Works great!
Do not forget to seal off the air intake at the metering plate.
Noted! That's a great idea.
 

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1991 560 SEC
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21 Posts
Discussion Starter #9
One more question: how many feet of vacuum hose do I need to replace all the lines?
 

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90 420SEL, 00 BMW X5, 00 Lexus RX300, 01 Chrysler Town and Country
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377 Posts
To seal off the air metering plate, I use a rubber glove. It works great.
 

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1991 560sec. 1991 560sel 1969 280SL
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1,333 Posts
One more question: how many feet of vacuum hose do I need to replace all the lines?
Most vacuum hose on these are nylon. AutohausAZ sells it in I think sells it in three foot lengths. They have a minimum for free delivery. I’d get some rubber vacuum hose also for the nylon ends.
 

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1999 500SL, 1988 SEC
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1,353 Posts
I think I purchased about 15 feet of the nylon and 10’ of the rubber. I still have some left but have not done the interior yet. Pretty cheap fix if you ask me.
 

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1981 300SD W126
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118 Posts
Reading this thread with interest. However, if looking to replace rubber vacuum lines why not use silicone lines instead? BMW used Silicone vacuum lines on my 79 320i but started to install rubber vacuum lines that degrade from heat cycling on the 2000 and up models. I replaced the rubber vacuum lines on the newer BMW with Silicone lines purchased from AutohausAZ. I don't see why you could not do the same for the MB. Anyone try it?
 

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1989 300SE 232k miles
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1,556 Posts
Reading this thread with interest. However, if looking to replace rubber vacuum lines why not use silicone lines instead? BMW used Silicone vacuum lines on my 79 320i but started to install rubber vacuum lines that degrade from heat cycling on the 2000 and up models. I replaced the rubber vacuum lines on the newer BMW with Silicone lines purchased from AutohausAZ. I don't see why you could not do the same for the MB. Anyone try it?
This is interesting. I’m always down for a replacement that lessens my long-term maintenance. I’d love to have others chime in.
 

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1991 500SEC 55K mi. 1987 560SEC Now 153K mi. 2020
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4,778 Posts
From past experience working on 2002s & 530is, I remember the BMW silicone vacuum line material to be exceptional quality over the standard rubber fare of the day.

Our V8 126s do have a short run of similar material plugged onto the EGR valve at the left exhaust manifold.
 

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Registered
1991 560 SEC
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21 Posts
Discussion Starter #16
Thanks for the silicone suggestion. I will give it a try. Where Can I purchase the silicon
tubing ? And what dimensions ?
 

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1981 300SD W126
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118 Posts
If you have a Caliper you can measure the outside diameter of the male end (OD) and this will give you the Inside diameter of the vacuum line needed (ID), you can also measure the outside diameter of the existing vacuum line (OD) and this should give you both dimensions inner (ID) and outer (OD) to choose which Silicone Vacuum Line size to get. Silicone Vacuum lines can be purchased online at places such as AutohausAZ, ECS Tuning, FCP Euro and places such as McMasterCarr. I have purchased from McMasterCarr high temp Silicone Hoses at an extremely low price per foot and available in colors if need be.
 
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