85 300SD Dead Turbo

1.) I will try to be succinct. The car I just bought has a dead turbo. There has been a lot of under the hood hanky panky in this car. (I wanted to learn something about diesel..well I hit a GOLD mine here.. ) The prior
owner/mechanic bypassed the Valve overload protection (Identified as item #21 in both the MB126 manual and the Haynes manual). The immediate question is where do you buy the transparent stiff hoses that connect the switch and ALDA (BTW...what does ALDA stand for???) capsule (overload protection capsule) and what are they made of? I want to get all the hoses back to stock position first. It seems they use black rubber hose off the switch then stick the clear stiff hose into that to the ALDA. 2.) Should you be able to turn the compressor wheel with your fingers or a small piece of wood? (item number #2 in the manuals) Mine is stuck solid. 3.) And finally where do you start on a dead turbo? The advice in the Haynes manual is.."Due to the special techniques required any checking or diagnosis of suspect problems should be left to your dealer." That's all it took for me to try to tackle this myself ( well sort of with a lot of help from some of you kind people out there) ! I had this car checked by my local dealer in Santa Rosa before I bought it and IMHO they did a really bad job. They pointed out the antilock light on the dash being on, the rear window broken, and the brake fluid was dirty. ( I am not blind and anyone could have seen that IMHO) I had a compression test done ($200 charge) and I am above 300 on all but one cylinder. They missed the failed right front wheel bearing ( squealing very loud) the missed the warped front brake rotors and missed the dead turbo. I am not clear if the receptionist did the work or one of the mechanics :-) In any event I am not using the dealer again! One of the other local mechanics took the car for a test drive with me and confirmed my suspicion that the turbo was not functioning. Thanks for any help. The only post I could find on this topic goes back to 2001 and is below from T.G. Lambach
As the turbo's pressure builds the ALDA allows additional fuel to be put into the engine for it's the fuel that makes it go, not the turbo's boost. That said, the only under performance will come about if the turbo's wastegate is adjusted to open prematurely, i.e. below 10 -12 psi when the engine is under full load at 4K rpm. Put a pressure gauge on the intake manifold to test the turbo's boost before doing anything with the turbo. The wastegate is what's to be adjusted, if anything.
M-B even included an overload protection switch (on the intake manifold) to avoid the engine running away if the wastegate were ever to stick shut, That tells me, anyway, that the ALDA will react to as much boost as is delivered to it and the M-B engineers wanted a way to cut off the boost being delivered to it!
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Could it have been Wolfgang Bley who typed:
|| 1.) I will try to be succinct. The car I just bought has a dead || turbo. There has been a lot of under the hood hanky panky in this || car. (I wanted to learn something about diesel..well I hit a GOLD || mine here.. )
Got the tee shirt................. snip.
|| 2.) Should you be able to turn the compressor wheel with your || fingers or a small piece of wood? (item number #2 in the manuals) || Mine is stuck solid
It should turn freely!! If it doesn't turn(siezed!!) thats your problem, It should spin freely when touched.
|| 3.) And finally where do you start on a dead turbo? The advice in || the Haynes manual is.."Due to the special techniques required any || checking or diagnosis of suspect problems should be left to your || dealer." That's all it took for me to try to tackle this myself ( || well sort of with a lot of help from some of you kind people out || there) !
I have played with turbos and even built one good from 2 bad! lasted 5K miles in the hands of a 20yr old!! would have probably lasted longer in normal hands.....
The problem is that it spins at 15,000+ revs so if the bearing, turbine blades balance and oil/supply are not perfect the turbo self destructs... This is why an exchange unit (with warranty) is the best way to go.
snip
|| M-B even included an overload protection switch (on the intake || manifold) to avoid the engine running away if the wastegate were || ever to stick shut, That tells me, anyway, that the ALDA will react || to as much boost as is delivered to it and the M-B engineers wanted || a way to cut off the boost being delivered to it!
These are to stop the turbo pushing more air and then more air etc etc untill the engine self destructs, so there has to be a limit to the ammount of boost!
One problem I have seen with turbos, is the bearing seals, go this pumps oil into the inlet manifold which then fuels the car and you can guess what the final oucome of that is!. The mess of the engine can be quite a sight.
Des
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The vacuum lines are available, but possibly not i the correct colors. There are different diameter lines, just oder a meter or two of each.

Yes.
Replace it with a good used one. THey're about $100, or have yours rebuilt at some place like Dallas Turbo.

300? 440 is normal.
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If the turbo's rotor doesn't turn easily with finger pressure then the turbo is very much kaput and must be replaced. Since it must be removed then you may as well remove it now and take it to a turbo shop or send it to its manufacturer for rebuilding. There's no option.
The rebuilt turbo should have a wastegate (pressure relief valve) attached and the wastegate should open at about 10 psi per M-B spec.
The oil supply to any turbo is vital, that's why the engine oil should be changed every 5K miles per M-B schedule; this engine probably didn't see such maintenance. I say that because turbos rarely fail, they usually last the life of the engine - 250K to 300K miles given routine maintenance and longer with excellent maintenance.
The ALDA is a set of brass bellows that contract upon boost pressure from the turbo. That contraction is transmitted through some levers to the fuel rack and additional fuel is put into the engine. Some owners "adjust" the ALDA for added power and usually also get lots of added smoke. The ALDA should be left at its factory bench setting, IMHO, a setting designed to provide decent power with minimum smoke. The ALDA can be broken during "adjustment" and all should know that it's NOT available as a M-B replacement part, but only from Bosch. So don't mess with it.
You have your work cut out for you.
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Thank you all for the great information. I will proceed as suggested and try to give you a follow up ASAP. Thank you again wolf
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