How it works - vacuum system on a 1982 380SL?

[300sdToronto]

Folks

As my handle suggests I have more of a background in diesels than gas engines, and I am in sales by trade so all of my knowledge of engines - such as it is - has been picked up by reading bulletin boards like this.

I did train as an electrical engineer and so have some basic logical thinking skills. I've successfully diagnosed and fixed problems with the climate control system and the cruise control on two different cards.

I have been diagnosing the dreaded high idle when warm problem and believe my idle control valve is working properly. Folks have been pointing me towards the vac system as a possible issue but I do not understand how it works or how the vac system influences idle speed.

It's hard to test a system you do not understand. If there is a post that explains the operation of the system I would much appreciate a pointer as searching vacuum produces just too many hits!

[dugald]

Over on Benzworld, member Nobby started a thread to collect information on the vacuum systems of the various model SLs. It may help you understand things.
http://www.benzworld.org/forums/r-c107-sl-slc-class/1453268-107-vacuum-diagrams.html

[strelnik]

Originally Posted by dugald

Over on Benzworld, member Nobby started a thread to collect information on the vacuum systems of the various model SLs. It may help you understand things.
http://www.benzworld.org/forums/r-c107-sl-slc-class/1453268-107-vacuum-diagrams.html

It's a great thread for SLs

[abiby]

You can spend a long time troubleshooting the system or you can very reasonably purchase a pile of rubber fittings and plastic tubing and replace it all.

A few hours is all it takes to replace virtually all the engine control lines and unless they've been replaced recently, they are all probably due.

I opted for the latter after gently pushing aside a line and having it break on me.

[coleyjf]

Originally Posted by strelnik

It's a great thread for SLs

What a great thread - I've been looking for the door-lock vacuum drawing for ages

Cheers

Jim

[rockcrusher]

What is your economy gage doing when the car is running, it should be pegged full left even at idle, if it's not you have a vacume leak, easy to check.