Turbo advice on '85 300TD
 

Greetings. We have an '85 300TD with 180k miles. My son has inherited the car from me and is his daily driver. We have replaced many of the key components, and are now Looking at fixing the turbo. The turbo has not functioned "normally" for several years, but we have not messed with it since the car runs great. I personally know how the car used to perform and the sound it made when it was working correctly. There has not been any "whine" or noticeable boost for some time now.

Visual inspection the other day shows that the turbine is spinning even at idle. I don't know if that is normal. I'm just a somewhat-experienced shade tree mechanic, but it would make more sense to me that the turbine would only spin when the turbo was engaged. Is that correct?

I'm wondering if perhaps there is maybe a valve stuck open (waste gate? apologies for lack of the proper knowledge and terminology). Wondering if there are some suggestions on how to test this (vacuum or pressure from the connected lines)?

We have had the car for >15 yrs and it's pretty clean, including the engine, and we have replaced most all vacuum lines under the hood, so there's not much visually that looks corrupt.

Thanks in advance for any suggestions and help!

In the archives there are several really good threads on fixing the turbo.. which is a very simple device and new bearings and rotor were very affordable the last time it was discussed...

If you have a bad switchover valve, it could also be the problem. It gets clogged up over the years and seriously affects the pickup. Just be sure to watch which plastic tube goes to which nipple and leave one nipple open to the atmosphere.

Might not be your turbo or this might be an additional problem.

The turbo will spin whenever the engine is running. It doesn't "engage" like a gear, it just spools faster as exhaust flow increases.

There are two possibilities. One is that there is some problem with the wastegate. I believe your model has a pressure operated wastegate, which is usually pretty foolproof. But the gate itself can become rusted in place. Often this can be repaired without removing the turbo by unclipping the actuator, spraying oil on the pivot, and working it free by hand.

But the more likely (usual) problem is that the pressure sense line or the switchover for the ALDA has become clogged. You can find a photo how-to here:

dieselgiant (DOT) com/mercedesaldaboostsystemservi.htm

Thanks

Banjo bolt is fine
 

I have checked this a couple,of times, and there is no soot on it. Blows clear.

Am I correct in understanding the there should be pressure (not vacuum) on the ALDA? What would be the method for testing? (I have a pressure/vacuum gauge to,use).

Thanks.

More advice in your duplicate thread, FYI:

http://www.peachparts.com/shopforum/diesel-discussion/391193-turbo-advice-85-300td.html

-Rog

Really simple. Remove the hose from the alda and plug it into your pressure gauge. There will be close to zero pressure at idle, and it will rise with RPM's. If this isn't happening, the flow path is obstructed with soot.

You should keep your questions in one post. The info people relate here is intended for everybody (not just you), and hard for others to find when spread over duplicate posts.