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  #1  
Old 09-06-2011, 12:23 AM
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Boosting Situation

Ok, So as some of you are aware I've been having issues with my car and boosting. I am willing to bet I have one of the slowest 124's around....

What I did--

Bypassed the overboost Switch
Result: No Smoke at idle, No other appreciable Difference

Blew Carburetor Cleaner through the boost lines (did not do this on the IM, the port appears to be clear)
Result: No Appreciable Difference

I installed a boost gauge between the ALDA and the intake and if my gauge is correct I get .5 PSI (half of a pound) boost pressure

I've also checked the air filter, Clean. The fuel system is clean. Filters have been changed within a few thousand miles, The tank vent is clear (as a precaution I did drive with the cover off, again no appreciable Change was noticed)

I've yet to check my turbo for Ease of spin, and lateral and Axial play yet. It's a pain in the butt to get to... So, Knowing these things, What else should I try, or is my Turbo sound like it's dead on it's bearings?

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Old 09-06-2011, 12:42 AM
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Not sure on MB but I've had turbos go out in a cloud of blue smoke Usually if the center bearing goes out it takes the seals with it and dumps oil in the intake. They are pretty durable items. How is the wastegate set up on these things? Internal I'm guessing...
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Old 09-06-2011, 12:46 AM
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Your wastegate could be partially open and all your boost is for naught.

Early models were pressure actuated - later involved a computer driven vacuum-driven unit.
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Old 09-06-2011, 12:50 AM
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It's possible. On the list of things to check when I take the air box etc out....again....
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Old 09-06-2011, 12:40 PM
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OK. Checked the wastegate it has full range of motion, Checked the VAC lines, found one busted that went to the EGR, I fixed the break and made sure there was a BB in the line to it, I took off the air intake the Turbo is very still to turn. there was some lateral play, but the turbo is hard to turn so seeing if it's spinning off balance is going to be difficult to do. I also fixed some random vac lines on that side of the car that were about to break too.
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Old 09-06-2011, 01:08 PM
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Under what conditions are you testing the boost pressure?

What does "full range of motion" mean in terms of a wastegate? They can leak.

My first suggestion would be to disconnect the downpipe from the exhaust and take a spin - see if boost changes. Other members have informed me that the catalysts are notorious for plugging up.
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Old 09-06-2011, 03:14 PM
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Judging by how hard my turbo is to turn by hand I am sure it's related. I had to push fairly hard to get it to turn.... I'm thinking something internal is either jamming or plugging. my exhaust flows pretty well about the same as a couple 300D's that a couple friends have. but it's worth a look.

on another note. seems like my vac leaks were plentiful. I fixed 99% to 100% of them and now my transmission shifts nice and smooth. Albeit the shift points are STILL off...
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Old 09-06-2011, 05:25 PM
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QUESTION NO.2:

How tense should the bowden cable be and where do I adjust it at?
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Old 09-06-2011, 05:43 PM
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Quote:
Originally Posted by jt20 View Post
Under what conditions are you testing the boost pressure?

What does "full range of motion" mean in terms of a wastegate? They can leak.

.
On a 617, what is the rubber line from the turbo down to the wastegate? I put a mighty vac on the wastegate side to see if it would hold vac and it will not. My 81 SD will only get 8psi WOT (gauge between mani and alta) with manifold banjo cleaned, over-rev bypassed, and EGR blocked off. The turbo spins freely with no wobble but has some fins chewed up.
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Old 09-06-2011, 05:47 PM
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The bowden should have zero slack in the cable.
Its adjusted by pinching the black plastic piece and pushing it through the bracket. Turn the two plastic pieces that are threaded in or out to achieve a "no slack" cable.
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Old 09-06-2011, 08:06 PM
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I should have asked that question Clearer.... Where can I adjust the bowden cable? where does it come up from and attatch to that it can be adjusted?
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Old 09-06-2011, 08:22 PM
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Should be the cable coming up from the Xmission on top of the aft of the valve cover with all the linkage attached to it.
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Old 09-06-2011, 09:54 PM
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Quote:
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Should be the cable coming up from the Xmission on top of the aft of the valve cover with all the linkage attached to it.
errr.... 603 not 617. no linkages on my Valve cover-
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Old 09-06-2011, 10:18 PM
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OK... .5 boost means the turbo is spinning somewhat... if it were jammed, you would have vacuum only.
with the engine running, can you see the turbo spin?
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Old 09-07-2011, 12:08 AM
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Quote:
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OK... .5 boost means the turbo is spinning somewhat... if it were jammed, you would have vacuum only.
with the engine running, can you see the turbo spin?
It dosnt budge unless I get the engine up to 15-1900RPM. it takes a lot to get it to go...

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