I've been working recently towards improving my gas mileage on my 300SD, especially since it dipped kind of suddenly down to 23 mi/gal. Found the reason to be an ALDA gone bad (threads had gotten screwed up in already otherwise pretty funky old unit). After I put in a replacement, I happily noted going beyond 500 miles on one tankful! YAY! So my question:

My overboost protection valve is stuck in protected mode (<== I get no boost when the unit is connected - but boost is present normally when I disconnect the black electrical wire from it). Has anybody ever had any luck cleaining these or should I just plan an spending another $50... I am guessing that it may have some kind of a diaphragm that might have gotten stuck 'closed' due to residue from years of sniffing in the intake manifold. Is trying to clean it just going to be time wasted?

Thanks in advance

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1983 300SD, 1999 200 cdi and 1998 1,6 (gasser)

Try cleaning it and see what happens. Can't make it any worse. It could easily be gunked up and stuck in the (electrically) closed position. (I am assuming that your are considering cleaning the sensor and not the valve itself.)

Yes, my bad...the pressure sensor. I'll give the cleaning a whirl tomorrow...Thanks!

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1983 300SD, 1999 200 cdi and 1998 1,6 (gasser)

If the sensor is stuck closed, it might have closed on it's own and stuck there.

Better get a boost gauge and make sure you are not getting more than 13psi.

1984 300d Turbo
Pull The Wire On The Over Pressure Switch Top Of Intake And Ground The Wire And Ign On You Will Hear The Switch Going To The Alda Pressure Line Close, No Pressure To Alda

The way I figured it out was that all of a sudden my boost gauge (connected currently post ALDA) was showing zero boost. I was doing about 65mph at the time (one way of experiencing the diff between a turbo and non-turbo, I guess). First I thought something had clogged the banjo fitting but figured I'd try disconnecting the boost sensor wire first - and that turned out to be the culprit.... I'll try cleaning it out tomorrow morning and then see if it responds to 12V. Thanks!

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1983 300SD, 1999 200 cdi and 1998 1,6 (gasser)