Vacuum leak diagnosis for 560SL
 

Dear All:

I have a rough idle problem with my ’86 560SL and after performing a standard tune-up (new plugs, ignition wires, dist. cap, and rotor) which was of no help, it seems the next thing to investigate is a vacuum leak.

Can anyone guide me to the relevant file on the MB Service Manual CD-ROM, as I can't seem to locate a vacuum diagnostics section? Otherwise (and assume I know little about the vacuum system but do own a Mityvac ), can anyone guide me through the logical steps to test and hopefully track down any vacuum leaks?

Any help is much appreciated.

Thanks,
Ryan Potts

'86 560SL

I'm sure there is an official procedure, but the easiest and argueably most effective solution is to grab a can of choke/carb cleaner with a straw attached and sparingly spray any potential offenders. If you hear (or see if you have a shop tach) an RPM increase, you found a problem. The vacuum source (atleast on my '80 450) is located at the back of the intake manifold behind the air cleaner (I had to remove the air cleaner in order to accomplish anything worthwhile). This procedure isn't much good if the leak isn't under the hood though. To that end, I disconnected and blocked the vacuum lines leading to my climate control and powerlocks beforehand.

I'll bet you a nickle where the leak is.
Checkon the drivers side, under the intake manifold. There are several lines thee that take vacuum from the intake mainfold and the can and doo come off. They are dificult to see, you almost have to stand on your head and use a mirror to see themproperly.
Hope this helps.
Barrie