I have a question about a brake booster check valve for my 69 220. PCV valve or in-line check valve needed? Recommended??

I replaced my Brake Booster on my 220 a few months back . . . was a rebuilt unit. Last week I discovered much to my dissapointment and frustration that the brake booster failed and was leaking air (could hear it when I would depress the pedal in the car) - UGH!

Sooo, I got a replacement (lifetime warranty) and installed it today, works great. I am concered though about gas fumes entering the brake booster since there was notes with the booster that says to make sure the booster does not get fuel or fuel fumes inside because it can ruin the rubber diaphram - well that makes sense . . . but since the vacume comes off the intake manifold, the inside of the booster will be exposed to fuel fumes when not in use and hooked to the intake. The booster did indeed smell of fuel fumes a good bit!!

Should I be looking for an inline check valve or use a PCV valve in the vacuum line from the intake to the booster? Makes sense to me - what do I look for? Is there some generic inline vlaves that would work well. I don't want the new brake booster fail on me again.

Thanks for your help.

Look forward to your help.

__________________
1969
Model 220 gasoline
Chassis: W115.010

There should be an inline check valve for this. Someone just lost it over the past many years.

The Mercedes dealer is probably the best place to pick up this part. It should cost about $15, but will last for 20 years.