Actually looking for someone in NE PA with MB diesel experience who might be interested in working on the problem. Either w/wo owner help. Or knowledge of MB dealer Leitzinger at State College Pa. Trusted diesel truck mechanic suggested them but with little first hand knowledge. I like working on MB but little time with teenagers. Took car to local MB dealer who took problem from no upper power(happened quickly versus over time) to intermittent by replacing 2 vacuum values and replacing contaminated fuel. He added a note "turbo wastegate line line may be in wrong". You have a port on the intake manifold and a line to diaphragm valve. What can be wrong? Called for more info but mechanic no longer there. Scarely.
Symptoms then what I've done.
In first ride home from dealer for 30 minutes, barely 40mph or 3,500 rpm. Slight sensation of engine "hunting" or slight surging. Then poof, more power, not like before so still missing some upper end power but can now do 50-60mph. Next day back to 40mph, drove for hour, no change. Sat for 2 monthes, back working on it. While driving mostly 40mph with couple minute busts of the 50 -60mph.
Thought I found source when I found dirt in banjo bolt, but no change on test drive. Vac valve on side of injector pump, just below ALDA has 1/2"+ stroke when actuated (sorry but I suck on it). Expect some movement and device to hold vacuum which it did. Loosened ALDA 4 bolt mounts and blew into its line. Could detect some movement but very little. Don't know what to expect but it held air. Vac solenoid in ALDA line works, tested on bench with power source and same vacuum source as stated earlier. At this point I might have done sometime wrong. In the solenoid and vac valve I squirted 3 in 1 oil. If problem is intermittent maybe the component sometimes sticks. So if oil is a bad long term thing then let me know.
Line between intake and exhaust is clear and vac valve appears to be ok. Took control vac line off and plugged but no change in drive test.
Waste gate valve holds air but I could not tell if I moved it or not.
Ran injector purge, changed both fuel filters and air filter before taking car to dealer. Dealer also changed both fuel filters so I'm confident the filters are ok.
Just read good article on adjusting ALDA which I have not done but I'm thinking that kind of tinkering would not be smart. Worried I might be over my head a little and make things worse.
Need to fix engine before worrying about fixing body . . .

Mark W
1983 300SD 225k
1986 250 Ford plow truck
1995 Bonneville
2004 Forrester Subaru
1980 Piper Warrior II, 180mph in a dive.

You have a more serious problem than an ALDA out of adjustment or no turbo boost. Without a turbo, this vehicle should easily do 60 mph and will go to 70 mph when pushed on the flat. So, forget about all those "adjustments" that you were considering.

It very much sounds like insufficient fuel or air in the system. Since you have changed both filters, make the following tests:

1) Remove the line from the primary filter. Does the fuel flow freely from the tank......or is there just a slight flow? Do this with a full tank of fuel.

2) If the tank if full of fuel, does the performance improve......or is it the same?

3) While running, do you see quite a bit of air in the primary? A large air bubble is normal. A lot of small bubbles is not.

4) Do you still have the old style primer pump.........the one that leaks fuel when you pull and push on the plunger? If so, get the new one and change the pump.

Report back with findings.

Do the fuel system checks that brian recommended (that might explain the hunting...ie...bubbles) and then if you still can't find what is up, throw a gauge on the pressure side of the turbo (tapping intot he ALDA line works nice) and see what sort of boost you are getting.

Maybe you have a stuck wastegate....maybe....doubt it though....


check for bubbles.

The vehicle has to go 60 mph, even with a wide open wastegate...........

1) Remove the line from the primary filter. Does the fuel flow freely from the tank......or is there just a slight flow? Do this with a full tank of fuel.
>>> 15 seconds for 2 oz. Blew line to tank with air, ran engine, same 15 sec on repeat test. Tried to get answer when Dealer replaced diesel fuel if they changed fuel tank filter. Did not get an answer. So I figured blow some air and see if flow rate changes. Nope.

2) If the tank if full of fuel, does the performance improve......or is it the same?
>>>Same for 1/4, 3/4 and full.

3) While running, do you see quite a bit of air in the primary? A large air bubble is normal. A lot of small bubbles is not.
>>>Dealer replaced my clear first filter with white one. Temporary installed 2 ft clear tube after 1st filter. Ran clear no bubbles at idle. Some very fast bubbles after taking RPM up then clear wiht fast small bubble now and then.

4) Do you still have the old style primer pump.........the one that leaks fuel when you pull and push on the plunger? If so, get the new one and change the pump.
>>> Yep have the one that leaks. Hope you mean change the manual primer pump 09-021 for $11.35 and not the Diesel Fuel Pump 09-084 for $180. If the fule is moving quickly and it only has to be presented to the injector pump which boosts the pressure this part seems to be working. I respect all the comments you have provided on all the posts I've read so far so I'll respect your ans.

5) In other posts I heard to check air lines for pluggage. So I pulled the air intake and exhaust manifolds as one unit. (Left the turbo connected together). Crud on all the walls but not deep at all. Thinking of cleaning anyway. Anything else I should do before I reconnect the manifolds? I'm going to replace oil seals on the drain lines and maybe clean air port walls but nothing else.

6) Second post said check waste gate and check boost. Will do. There is another port capped off around the corner from the ALDA port. Wouldn't this be a better place to get boost pressure versus tapping the ALDA line?

Thanks for the help. I'll be gone for a day but back tomorrow to order parts. Found some time to work on MB by taking the day off. This could become a habit!

7) Side question. Turbo oil drain line to just above oil pan is not pulling out. Tried to turn but no progress coming out. Assume harden rubber and just pull harder? I"ve already broken somes things along the way and want to minimize further side jobs.

Mark W

1) 15 seconds for 2 oz. is probably fine. Intuitively, I feel it should be more, but air forced back through the lines would open the strainer and the flow would increase.........if the strainer was clogged.

2) With the same flow at different tank levels, this further confirms that the strainer is probably fine.

3) When you say "some very fast bubbles after taking rpm up"........please explain in more detail exactly where these bubbles appeared.......if they did not appear in the primary.

4) Yes, please change the manual primer pump to the new style pump (black plunger). It's available from Phil, right on this site.

5) You can clean the inside of the intake, if you feel really industrious........but it won't affect the problem with reduced power.

6) Same issue with the wastegate. Make sure it's operational, but, that's not the primary issue.

7) That job is quite a task to do properly and it usually involves dropping the lower oil pan. There are some threads on the procedure.......Dave Morrison seems to stand out in my mind as the member with the most detailed procedure for it. I would not remove this line unless it's leaking badly at the oil pan.

Keep us updated,

When I got my 300SD it would NOT break 60MPH unless I had a hill behind my back.

Plugged ALDA line, possible old fuel filters, low boost, virgin ALDA...

That thing was "entertaining" to drive home heh....its far from slow now

Brian;
3) Primary or the first filter which is small. Dealer put a white opaque filter you can not see inside of. So I removed the 2" long black hose after the filter and installed 2 feet of clear hose. (The hose used to flus hthe injectors). After hand priming, fired the baby up. Couple bubbles moved slow though the line, assumed source was breaking the line. Line then cleared up and did not see anything. So I increased rpm. Now and then something would shoot through the line so fast I couldn't really see it. (clear hose was coiled about 4 times.) I could see something in the first coil but had trouble seeing anything in the other coils. Thats moving pretty fast. So I kept bumping the rpm to see more of these. Did not normally get more but every now and then someting would shoot through. I believe this part is working ok unless the fuel should not be moving fast.
4) I'll look for "Phil" on this site for the new plunger. I usually purchase from Performance Products. I do have need for a number of gaskets that are accumulating and may do just one order. I'll view MercedesShop as well.
6) Wastegate. It held air with everything together but did not feel much movement. Should be able to check better with everyting apart. By the way is the "wastegate" the "boost pressure control valve?" Takes exhaust air around the exhaust blower right. Signal is from air pressure just at start of air blower housing. 6.1) There is a stainless steel air line that feeds to exhaust manifold. The vacuum valve controlling this line is mounted on the air manifold. The air port in the supply manifold feeding this line is 5/8" x 1" and is 90% plugged. But since I believe it acts as a second way to lower boost pressure do not think it is the primary probelm.. I'll check to see if this thing is alway on, hense why the feed port is full of gunk. Vacuum signal for this comes via a couple engine mounted components and actuator on top of engine. It was this device I took loose and not the wastegate. I really have not found this device on any views yet.
7) I dropped the oil pain a year ago. Yes the turbo oil return/drain line leaks bad enough to fix. Oh well, but very good I didn't keep on pulling . .

Brandon:
Tell me more about this "Virgin ALDA . . .Are there different or newer designs?
" I found a good thread on how to adjust ALDA with the engine running (didn't do it though) but do not know how to test in place. Vacuum valves I suck on and want vacuum to hold, (no leaks) and you can usually see/fell/tell something moved. For ALDA check I loosen 4 mounting bolts but when I blew in the line I felt very little movement at all. Seemed to hold pressure. Figured I could not blow hard enough. I do have access to air so I could rig a fixed pressure if I knew how much movement to look for. (14 inches a typical boost pressure?)

Having fun again thanks.

Mark W
1983 300SD 225k
1986 250 Ford plow truck
1995 Bonneville
2004 Forrester Subaru
1980 Piper Warrior II, 180mph in a dive.

3) That setup sounds fine. I can't quite figure out what is flying down the tube........but it seems insignificant.

4) "Phil" is the fellow who runs "FastLane" the parts supplier on the forum. Just press the "FastLane" button at the very top of the first page. PP is also fine for any of these parts.

6) "Wastegate" and "Boost Pressure Control Valve" are one in the same.

6.1) I believe that you have found the EGR valve. It's mounted to the intake manifold and has a stainless corrugated steel tube that leads down to the exhaust manifold. It's a common cause of excessive buildup in the intake manifold. Simply pull the vacuum to the top of this valve and plug the hose. Alternately, if you want to remove the valve completely, I sell a kit that allows you to put a stainless steel plate in place of the valve. The valve is not the source of problem.........unless it's stuck in the full open position. When the valve is off the vehicle, make sure that the diaphragm, on the bottom.....is seated when no vacuum is applied.

7) Do a search on the forum for "turbo" or "drain". There are threads that detail the removal of the tube and the replacement of the grommet that lead into the pan. Post again if you can't find it.

A "virgin ALDA" is nothing more than the original setup from the factory that prevents tampering. Around and above the screw is a sheet metal can with a plastic insert. It prevents you from getting to the adjustment screw. You need to remove this anti-tampering device....carefully.....to access the adjusting screw. Most older vehicles have the screw accessible.

The ALDA takes pressure. You can apply up to 15 psi. However, you won't see any movement because the movement occurs in the IP. You can remove the ALDA and observe it's motion after pressure is applied. IIRC, it moves about 1/4" or so.......maybe slightly more.

Do not remove the four mounting bolts. They hold the unit together and all function is lost when it comes apart. The ALDA is removed from the single large hex nut underneath. 27mm seems to stand out in my mind. You need two wrenches. One to hold the locking nut and one to turn the ALDA.

Ordered parts form Phil but one gasket short. Will be a couple more days before exhasut and intake get bolted back to engine. I believe I may have found the problem. Remember how the Dealer stated the waste gate line might not be ocrrect. Then I didn't know about the EGR valve. Figured Dealer might have make the same mistake. I have added how the vac system is connected and I believe it is wrong. Supply vac is going to the transmission. I believe it should go through the vac relay next to the ALDA. But then I'm not sure what to do with the other line. I've attached what I have. I'm hoping someone can provide what it should be. Thanks.

Brian. I took your advice and looked up threads on removing the turbo oil drain seal from oil pan. It helped a lot. I needed the info there but then improved on it. So I'm going to add to that post next.
20 minutes later I'm still not sure the attachment worked. I'll check after after posting.

Mark W
1983 300SD 225k
1986 250 Ford plow truck
1995 Bonneville
2004 Forrester Subaru
1980 Piper Warrior II, 180mph in a dive.

Attached Thumbnails

 

We're going to make this very simple for you and you'll be thankful when we are done.

You have the source vacuum from a T near the VCV (next to the ALDA) to the black box on the valve cover.

Get rid of this line and plug the end by the VCV.


Now, you have a second line coming from the valve cover and entering a T with the line that comes out of the side of the VCV. These lines merge at the T and then head inside the cabin.

Get rid of this line and eliminate the T. Connect the line from the side of the VCV directly to the line that enters the cabin.

So, we now have a black box on the top of the valve cover with only one line coming out of it and headed to the temperature switch, correct? Well, we don't need that line either.

Get rid of this line.

Now, we have a black box with nothing connected to it, correct??

That's what we wanted all along.

OK. Will do. That means the automatic transmission gets full vacuum all the time? Didn't think that was right.

Will put everything together and see if the originally problem is gone. You can only hope.

Mark W

No, it definitely does not.

The supply vacuum must have a restrictor in the line.......before the VCV. This limits the amount of air that can pass through the restrictor. So, the VCV can then provide a controlled bleed to drop the vacuum to the transmission depending on throttle position. It certainly cannot control vacuum if the supply is unrestricted.

So, check carefully to see if you have this restrictor. It's nothing more than a plastic connector with two vacuum nipples protruding from either side. You can easily miss it in the line if you don't look carefully. Just look for a very narrow piece of plastic right in the middle of the vacuum line to the VCV. That's the restrictor.

If you don't have the restrictor, the system can't function as designed.

I feel I'm close but not there. Back to the vac diagram I made. Box above "modulating pressure automatic transmission" (these words are from MB diagram), next to ALDA, you called this VCV, is green. Size approximately 1 inch cylinder. Could very well be a restrictor you talk about. It would make sense for the vac line to transmission to come from the bottom of the VCV and not from the vac source/pump. So the question is; Remove transmission line from vac source and plug source and then install transmission line and tee into line, bottom of VCV and line to car?

Mark W

Nope, not there yet.

Back to the vac diagram you made.

Box above "modulating pressure automotic transmission". This is a 1" cylinder that is a vacuum damper. It's not the VCV. The "VCV" is the vacuum control valve and is a white plastic device down below and to the rear of the ALDA. It controls the vacuum to the transmission. The 1" cylinder is directly above the VCV and feeds the top of the VCV.

The restrictor is NOT the vacuum damper. It's about 1/10th the size of the vacuum damper. If you don't look very closely at the vacuum lines, you won't see it. But, you MUST have it installed for the system to function. If the PO was a moron, he probably replaced the vacuum lines and eliminated it.

No. Vacuum source feeds VCV through (1) orifice and (2) damper. Source continues (after T) down to transmission.

Line from side of VCV goes into cabin (vent line).