I wanted to check the boost pressure created by the turbocharger so I connected a 0 to 15 psi gage to the intake manifold connection located just behind the air filter housing. I am getting 12 PSI at WOT while driving but I also am getting a pulsing or fluttering of pressure. At full boost the pressure gage needle fluctuates very rapidly, a blur really, about 1 PSI. AT idle the pressure is 0 PSI but I can hear the gage being sucked down against it's stop rhythmically which makes a clicking sound. My guess is that this may be caused by uneven compression across the cylinders. Are there any other possibilities? I am gong to by a compression gage this week, I only have one for gas engines now.

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1984 300CD (sold)
1973 220DPK 4 spd (died)
1978 350SL 4 spd gray market
2003 SLK32 AMG
1988 300CE (sold)
1997 E420 (Totaled)
1998 E320 Wagon

I would think this is the normal effect of the wastegate.

There were details given long ago which indicated that the turbo life starts to drop dramatically after somewhere around 11.7psi...

So being at 12 seems good to me.

The fluctuation? I don't see that on my gauge on my w123. I wonder if you have a weak wastate or something. It could be the case. Might be smart to add a boost controller in series...

Also clean out all the connections.

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
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1993 300SD (291k)
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1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)