Recently my trusty 240 hasn't been turning off with the key. I had this problem before and it was a vacuum leak in one of the Y connections. This time it sounds like it's inside the brake booster. My brakes feel completely fine so I'm wondering if there is anything i can do to confirm if that's where the leak is without taking it Apart.

To test a brake booster, you run the engine, confirm that there is power assist, and turn the engine off. The booster should hold vacuum for hours. So, turn off the engine, wait a few hours, then press the brake pedal and see if you have assist for a pump or two. If not, the booster or the check valve is leaking.

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'84 190D 2.2 5MT (Red/Palomino) Current car. Love it!
'85 190D 2.2 Auto *Cali* (Blue/Blue) *sold*
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That is very helpful. I can hear a leak but can't find it. I've checked all the small hoses in that area and can't find anything

Does your booster fail this test?

The other thing you could do is go around with a mityvac and mechanic stethoscope and test different lines and components while listening at the same time.

__________________
'84 190D 2.2 5MT (Red/Palomino) Current car. Love it!
'85 190D 2.2 Auto *Cali* (Blue/Blue) *sold*
http://badges.fuelly.com/images/sig-us/302601.png
http://i959.photobucket.com/albums/a...0/sideview.png

I tried the test a couple hours after i ran the car and it seemed to still have assist but then i tried it after the car sat over night and had no assist