Originally Posted by pmckechnie

Having worked on intermittent problems many times I would like to suggest you connect a vacuum gauge to the vacuum system so you can see when the problem is there and when it is not. It may be failing more often than you think and a gauge would help you know when it fails. For instance, on your 5000+mile trip, it could have failed many times but you didn't know it because it didn't fail when you were turning off the engine, locking the doors, etc, at that exact time. If I am not mistaken the 380SL had a economy gauge in the instrument panel which is just a vacuum gauge. If it is still there you could use it as an indicator. You don't need to know exact readings, just an indication that something is not right. Then you could disconnect different systems, one at a time and be able to see if the problem has gone away. If not, go to the next system. Get the point? Then after the problem is found and fixed you can keep the gauge connected and you will have an indication of the vacuum system health.

Paul