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  #1  
Old 08-22-2015, 07:44 PM
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Surging, turbo not regulating??? Help

I'm still around. Haven't been lurking here in a while as I bought a four letter word to drive and been working on a tone of other projects. The benz has been more dependable by far so don't give up.

I do have a problem that's cropped up. The benz is 1982 300 turbo diesel with about 145k. The problem seems to be with the waste gate or the regulation of the turbo boost pressures remaining steady, so it feels like it's surging while cruising or going up hill. Almost feels like it's starving for fuel but that's not the case.

Anyone else have an issue like this that's been solved?

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  #2  
Old 08-22-2015, 08:16 PM
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How do you KNOW it is not starving for fuel ?

When did you last clean or replace all your filters ?

Edit... that question includes the one in the bottom of your fuel tank....

Last edited by leathermang; 08-22-2015 at 10:43 PM.
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  #3  
Old 08-22-2015, 09:37 PM
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I read in another thread that it could be too high of a crank case pressure shutting off the rack via the vacuum shut off. This could be the problem. Has anyone ever taken apart the oil separator in the air filter housing? It seems I may be having a restriction there. Or the air filter is also pretty bad. No air through the filter the turbo can and will intake air from anywhere it can including from the brank case breather.

As for the fuel issue I've checked the fuel tank sock lines and both filters have been changed. The stumbling goes in and out and sometimes feels like a temporary full boost from the turbo, to excessive egr on a gasoline motor.
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1984 280SEL, 62,000 miles
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1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)
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  #4  
Old 08-22-2015, 09:51 PM
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First step should be to clean the alda connections:

Mercedes ALDA boost system service

90% of the time that will do it.
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  #5  
Old 08-22-2015, 10:40 PM
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Way too complicated. Start with the small and sensible things first. Change out your filters again.
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  #6  
Old 08-22-2015, 11:01 PM
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"Way too complicated. Start with the small and sensible things first. Change out your filters again. "

Complicated? How many times do you change the filters before you figure out it's not the problem? I guarantee that any diesel that's run for a length of time needs the alda lines cleared. Let it go long enough, and the Alda functions as a fuel restrictor rather than a booster.
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Old 08-22-2015, 11:29 PM
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"I read in another thread that it could be too high of a crank case pressure shutting off the rack via the vacuum shut off. This could be the problem. Has anyone ever taken apart the oil separator in the air filter housing? It seems I may be having a restriction there. Or the air filter is also pretty bad. No air through the filter the turbo can and will intake air from anywhere it can including from the brank case breather."

It's next to impossible to have high pressure in the crankcase with a turbo car. If you could install a pressure gauge on your valve cover, you'd find that the crankcase is under negative to neutral pressure almost all the time. If this isn't the case, it would be due to bad rings or valve seals. This is because the turbo draws air like a shop vac, even at low rpm's.

The separator in the valve cover works like a PCV valve. It prevents the full vacuum of the turbo from acting on the crankcase: it's supposed to be a restriction. If it wasn't restricting vacuum, the turbo would suck all the air, oil, and loose parts out of the valve area and crank case. Your engine would surge not sag, because it would be fueled with engine oil as well as fuel. You'd also be leaving a fine black smoke screen in your wake. Oth, if the separator valve was stuck closed, crankcase pressure will build until the car stalls. You'd also be spewing oil out of the weakest seals on your motor. But do change your air filter.

To directly answer to your question, I know of nobody who's disassembled the valve cover components and written about it. This is because the assembly is held in place with rivets of some sort, which appear to be non-removable. Another brilliant Mercedes design: if the separator valve fails, replace the entire valve cover. I'm hunting for a cheap valve cover to experiment with, so watch this space.
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  #8  
Old 08-23-2015, 01:53 AM
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Quote:
Originally Posted by Mxfrank View Post
"I read in another thread that it could be too high of a crank case pressure shutting off the rack via the vacuum shut off. This could be the problem. Has anyone ever taken apart the oil separator in the air filter housing? It seems I may be having a restriction there. Or the air filter is also pretty bad. No air through the filter the turbo can and will intake air from anywhere it can including from the brank case breather."

It's next to impossible to have high pressure in the crankcase with a turbo car. If you could install a pressure gauge on your valve cover, you'd find that the crankcase is under negative to neutral pressure almost all the time. If this isn't the case, it would be due to bad rings or valve seals. This is because the turbo draws air like a shop vac, even at low rpm's.

The separator in the valve cover works like a PCV valve. It prevents the full vacuum of the turbo from acting on the crankcase: it's supposed to be a restriction. If it wasn't restricting vacuum, the turbo would suck all the air, oil, and loose parts out of the valve area and crank case. Your engine would surge not sag, because it would be fueled with engine oil as well as fuel. You'd also be leaving a fine black smoke screen in your wake. Oth, if the separator valve was stuck closed, crankcase pressure will build until the car stalls. You'd also be spewing oil out of the weakest seals on your motor. But do change your air filter.

To directly answer to your question, I know of nobody who's disassembled the valve cover components and written about it. This is because the assembly is held in place with rivets of some sort, which appear to be non-removable. Another brilliant Mercedes design: if the separator valve fails, replace the entire valve cover. I'm hunting for a cheap valve cover to experiment with, so watch this space.
Please note that when My Engne is idleing if you obstruct the opening on the Valve Cover with your thumb it takes about 7 seconds and the Engines starts to stumble and shut down.
A restriction in the Crankcase Vent System will indeed shut you down.

Also one Member covered that port for too long and the front Crankshaft Seal popped out.

Also a lot of folks have issues with Oil from Crankcase Vent Blow By making an oily mess in their Air Filter Housing and that is not consistant with the Crankcase pressuer being negative.

I disagree with this. Except for sime pin hole that people have said is in the Valve Cover there is no way any sort of vacuum could suck anything out of the crankcase. It would be like trying to suck on a straw with your finger covering the other end of the straw.

The other issue is on the inlet side of the Turbo if there is a Vacuum you are going to suck Oil past the Shaft Seal out of the inside of the Turbo Charger and into the compressor side of the Turbo Charter.
I have seen that happen quite a few times on Big Rig Trucks where the Air Filter got plugged.

Except for the Older Mercedes Engines that used a Pneumatic Governor with a Butterfly Valve in the Intake Manifold there is not supposed to be any Vacuum in the Inlet before the Turbo or that intake Manifold (assuming the Turbo is working like it is supposed to).
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Last edited by Diesel911; 08-25-2015 at 10:53 AM.
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  #9  
Old 08-23-2015, 04:42 PM
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When you hold your thumb over the grommet, you will of course build pressure because you've removed the connection to the turbo. The turbo inlet will always be under negative pressure, and as long as there isn't a lot of blowby, it will evacuate the crankcase. An easy way to test this is to open the oil filler cap and let it lay on top of the opening, so the seal is in contact with the rim. If you carefully lift it, you can feel the suction. Rev it a bit, and the suction increases. Disconnect the turbo by removing the breather tube and you get the tea kettle effect, due to blowby pressure. Mercedes themselves acknowledges that the turbo can suck oil out of the engine, and that's what the separator valve is supposed to prevent. I didn't invent this idea. See any of the 60x FSM's that explain the workings of the oil/air separator.

The pinhole in the side of the valve cover doesn't open all the way into the valve area. There is an aneroid disk inside the top of the cover which controls the separator valve. The disk faces into the valve area, the back of the disk has to be exposed to normal atmospheric pressure so that it can sense pressure changes. This is what the hole is for.

You aren't going to suck oil past the turbo seal, because the compressor wheel pressurizes everything behind it.
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  #10  
Old 08-23-2015, 09:03 PM
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Quote:
Originally Posted by Mxfrank;3511630[COLOR=red
]When you hold your thumb over the grommet, you will of course build pressure because you've removed the connection to the turbo. [/COLOR]The turbo inlet will always be under negative pressure, and as long as there isn't a lot of blowby, it will evacuate the crankcase. An easy way to test this is to open the oil filler cap and let it lay on top of the opening, so the seal is in contact with the rim. If you carefully lift it, you can feel the suction. Rev it a bit, and the suction increases. Disconnect the turbo by removing the breather tube and you get the tea kettle effect, due to blowby pressure. Mercedes themselves acknowledges that the turbo can suck oil out of the engine, and that's what the separator valve is supposed to prevent. I didn't invent this idea. See any of the 60x FSM's that explain the workings of the oil/air separator.

The pinhole in the side of the valve cover doesn't open all the way into the valve area. There is an aneroid disk inside the top of the cover which controls the separator valve. The disk faces into the valve area, the back of the disk has to be exposed to normal atmospheric pressure so that it can sense pressure changes. This is what the hole is for.

You aren't going to suck oil past the turbo seal, because the compressor wheel pressurizes everything behind it.
The non-turbo Diesels have a similar crankcase vent setup.

There is indeed Air Flow in the Intake between the Air Filter and the Turbo but there is no vacuum unless there is a restriction like an pugged Air Filter. And, that is where the Crancase vents goes.

On some Turbo Diesels there is simply a Hose going into the Intake (with no valve) from the Valve Cover and on others there is a Hose going to a Breather/Oile Seperator built into the Air Filter Housing with a one way valve at the bottom of the Oil Drain Tube.

On both the Vapor from the Crankcase Breathing system gets pulled in to the Air intake by the Air Flow.

If you have an a Vacuum in the Intake on a Turbo Diesel then our intake is restricted or too small.

This is from Chilton's guide to Diesel Cars and Trucks from 1983 which is after the time the Mercedes Deisels were on the Road and
"The Diesel, by nature of its operation, does not generate engine vacuum as to gasoline engine counter parts."

Why does a diesel engine not produce enough vacuum

Why does a diesel engine not produce enough vacuum
"As a diesel engine does not have a throttle valve in the air intake, no useable depression is created in the intake manifold. That is why diesel engines are fitted with vacuum pumps to operate the brake servo."

Now I have made some effort so support my argument. Please supply some info that supports your argument that there is a Vacuum in the Air intakeb between the Turbo and the Air Filter on Turbocharged Diesel Engines.

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  #11  
Old 08-24-2015, 05:48 PM
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Today read that rack damper bolt adjustment might fix your exact problem.
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  #12  
Old 08-24-2015, 09:41 PM
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Originally Posted by Diesel911 View Post
Now I have made some effort so support my argument. Please supply some info that supports your argument that there is a Vacuum in the Air intakeb between the Turbo and the Air Filter on Turbocharged Diesel Engines.
Instead of sitting in your chair, get up, start your car, and experiment. You're going to find that there is always a negative pressure in the accordion tube. Or, check the manual, I've even attached a page for your perusal.
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Surging, turbo not regulating???  Help-60x.jpg  
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  #13  
Old 08-25-2015, 10:51 AM
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Originally Posted by Mxfrank View Post
Instead of sitting in your chair, get up, start your car, and experiment. You're going to find that there is always a negative pressure in the accordion tube. Or, check the manual, I've even attached a page for your perusal.

Thank you for posting something that takes it beyond opinion.

On My Engine there is no pressure Control Valve in the Crankcase Vent System and no liquid Oil get sucked out of the Engine and there is no Throttle Valve in the intake to create a vacuum. So if I tested it I would not get the same results as a 60X Engine listed on the manual page.

I blew up the text of the page and it explains what causes the vacuum in the intake manifold as being a Throttle Valve.

So it seems clear to me from what you posted it is the Throttle Valve that is causing the Vacuum not the fact that it is a Turbocharged Engine.

That is not inconsistent with what I said. "There is indeed Air Flow in the Intake between the Air Filter and the Turbo but there is no vacuum unless there is a restriction like an pegged Air Filter. And, that is where the Crankcase vents goes."


As I mentioned the older Model Mercedes that use a pneumatic Governor have a throttle/butterfly valve in the intake Manifold and that and a venture creates the vacuum in the intake manifold that is needed for a Governor.
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Surging, turbo not regulating???  Help-mercedes-60x-throttle-valve.jpg  
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Last edited by Diesel911; 08-25-2015 at 11:06 AM.
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  #14  
Old 08-25-2015, 03:38 PM
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One diagnostic is to monitor intake boost pressure from inside the cabin. I put a T in the plastic tube from the intake manifold and ran a nylon vac tube thru the rubber grommet to a gage in the cabin to monitor while driving. Some have made that permanent (gage where cigaretter tray sits). At the same time, unscrew the intake banjo bolt and clean it out (as mentioned).

You don't know what you will find. I did above when a newly swapped engine wouldn't let my 1985 go faster than 5 mph, which was strange since it ran fine when I tested it on the ground. The vac gage showed ~20"Hg vacuum in the intake as I tried to accelerate. As above, while normal for a gas engine, a diesel should have almost no intake vacuum other than the slight air filter drop. Caveat - some M-B diesels do have a throttle plate (post 13). I popped off the plastic elbow and found the wad of paper towels I had stuffed to keep debris out of the turbo inlet. My punishment for re-assembling after dark. Ran great w/ no air restriction.

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