Hey Guys,

I just bought this '83 300 SD to run on WVO and it seems really slow. I can't hear the turbo spin up, but it turns by hand easily. It is pretty oily on the front (intake air? side). Is that a bad thing? I think I remember something like that. How hard is it to rebuild a turbo? Is it possible to run the car with the turbo out for repair? Will it just be a non-turbo or is it not that easy?

The other thing is the AC robs almost all all of the power. Is it normal for it to be really noticeable on even a regularly running engine? It seems that there must be too much drag on the compressor or some part. Could I lubricate it? Also, where would you add or check the level of R-134?

Thanks,
Nick

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1983 300SD running on WVO soon, bought for $750!

the intake side may be just blowby. have you checked for blowby? if it has a lot it may just be tired. and that would go along with the other symptoms of low power, etc.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

You have drawn the conclusion that the turbo is the culprit, when, typically, there are many other things to check first.

On older M/B that have "no power" the very first thing is to remove and clean the banjo fitting and the line to the overboost valve. This typically clogs with carbon over time and eliminates the fuel enrichment.

You can find the banjo fitting on the very back of the intake manifold. Remove it and thoroughly clean it, and the plastic line that runs to the overboost valve.

Then, pick up a boost gauge. It's necessary to determine if the turbo is working properly. T in the gauge between the overboost valve and the ALDA.

The ALDA is the 2 inch diameter round cylinder on the injection pump that provides the fuel enrichment. The overboost valve is on the firewall. The line from the banjo fitting runs to the overboost valve.

A properly setup SD should have boost in the 12 psi range. Most of them will be about 9 psi. This is fine and is telling you that the system is working properly. You can increase this value in the future by investigating how to adjust the wastegate.

The turbo is rarely the culprit when the complaint of "low power" is presented.

Ditto about the banjo fitting and line to the overboost valve.

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Growth for the sake of growth is the ideology of the cancer cell. -- Edward Abbey

1984 300SD: Hilda the veggie vundercar

Hi Brian,

Thank you for the insight. I was wondering where the ALDA was. What does that stand for? I had turned a little black knob near the IP and the brake cylinder. Was that it? What will it affect?

Are there any good websites for repairs that have pictures? That would be cool.

Thank you,
Nick

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1983 300SD running on WVO soon, bought for $750!

"ALDA" is an acronym for something that I can't remember anymore. Somebody chime in.

I'm not sure which black knob you are speaking of. Was it on the IP or on the master cylinder reservoir, or what??

Take a look on the first page of Diesel forum. There is a sticky there that has all kinds of links for repair of a W123. Many of these are also applicable to a W126. It's a good place to start.

NickL,
Here's a photo of the ALDA on my 1982 300SD engine. It's the square with the round top in the center of the photo. It sits in front of the oil filter housing, and behind the fuel injector pump. It can be adjusted by turning the screw in the top, though many of them are covered over with black plastic so you won't be tempted to adjust them. There are many posts on how to adjust it, so do a search for how-to's. Good luck!
SteveKaa
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1982 300SD 355k miles

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Tweaking the Alda should be the last thing you should do however. Ensure all else is in working order first. As Brian mentioned, check for boost enrichment first. This will give you sluggish sled-like performance. Once that is done, fuel filters and valve adjustment are in order.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Hi Brian,

I found the banjo fitting on the back of the intake, I think. Is that just behind the airfilter and hard to see by the firewall? It has a clear vacuum hose coming from it and going toward the ALDA/master cylinder. It was really dirty and clogged. I was going to replace it, but do I need to use the clear tubing? Where do you think I can find that kind of tubing? How would you clean the banjo device? (what does the banjo device do?)

If I hook up a vacuum tester to it, what should I see? I'm new to that, is there any kind of manual with pictures of where to test and what readings you should see?

What should I see after getting the line cleared there? What would be the next step from there?

Thank you for your help!

Nick

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1983 300SD running on WVO soon, bought for $750!

That's it.

Don't even bother to try and replace just the clear tubing. Go to the dealer and buy the proper part. It includes the tubing and the fitting on the end that will fit the banjo bolt. You still need to clean out the banjo bolt. That hole through the middle must be clean. Use Brakekleen and spend 30 minutes with it, if necessary. You can't get the tubing off the old part and put new tubing on and hope that it remains in place.

The banjo bolt simply screws into the manifold and allows pressurized air to pass through the middle of it and onto the overboost protection valve.

No vacuum tester! If you want to test it properly, you need a boost gauge. The line sends pressure to the overboost valve and then onto the ALDA. This is what gives you the fuel enrichment.

After you buy a new line and clean the banjo fitting, then check out the overboost protection valve. It also needs to be clean, but, since it's plastic, the Brakekleen might not be such a great idea for it. See if you can use compressed air to blow out any carbon traces.

Once you get it back together, and purchase a boost gauge, you can T the gauge into the line from the overboost valve to the ALDA. Route the gauge into the cabin, via the driver's window, and take the vehicle for a drive. Put it in third gear and get the revs up above 3000 rpm with maximum pedal. See what the gauge reads. Report back.

Hi Brian,

Great news, my friend and I cleaned the banjo fitting and ran new vacuum line over to the overboost valve. It made a great performance improvement because the other one was totally clogged.

I drove over to his house with the line not there and the car was really, really slow. I noticed it blew a little oil out of the manifold and onto the engine from the banjo fitting. Is that normal? I just realized that probably was what clogged the old vacuum line. Should I try to fix that oil problem?

I'm going to get a boost gauge and report the results. I think that I heard the turbo for the first time! How long should I let it spin down after driving? Does it just depend on how hard you were driving that trip?

Thank you,
Nick

__________________
1983 300SD running on WVO soon, bought for $750!

knob is on some of the newer cars. i understand it is to adjust the fuel somehow. i think my 90 has it but i havent tried anything with it.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Yep, that's what they do over time. Cleaning that line and the banjo bolt should be part of your maintenance procedures. If you do it once per year, it won't get so bad that the line must be replaced.

Depending on the condition of the engine, all diesels consume some of their lube oil. The blowby gas is saturated with oil and some of it is sent to the engine after it leaves the oil separator in the air filter housing. The more wear on the cylinders and rings, the greater the blowby. You can't fix this problem without completely rebuilding the engine, so, in your case, just pay attention to cleaning that line on a periodic basis.

The turbo will spin down within seconds after you lift your right foot. The issue is the temperature of the turbo. If you just had the vehicle on a hot, hard run on the highway, you don't want to shut off the engine immediately after pulling off the road at a rest stop. 2-3 minutes of idle will allow the turbo to cool sufficiently so that you don't cook the oil in the turbo. If you run synthetic oil, there is much less chance of this occurring and, it's likely that you wouldn't need any idling period at all. I run synthetic and I still let it idle for two minutes at the rest stops, no matter what the ambient temperature. Probably overkill, but, I like it that way.

a bit of an aside here... bu reading all this got me curous and I went out ad looked for my banjo bolt to see if it needed cleaning and it doesn't seem to have one (87 300 SDL). Looks like my engine has a line coming off the intake manifold, through some valve/cntroller of some kind, and then to the alda unit. That's the only connection between the alda and the intake manifold.

So I guess the 603 doesn't have the banjo bolt? I guess I'll just clean out these other lines that seem to erve the purpose.

Charlie

.. quick update ... I found the fitting - not so much a bolt but a fiting in the case of the 603. Anyway I took that off and cleaned it out with some injector cleaner and a handful of pipe cleaers. It was pretty carbonized in there, but far from plugged. Will report whether it made noticiable diference or not.