Hi all,

I acquired a 1987 300d with 250000 miles and have been repairing it over the last few days.

Done so far:
1. New glow plugs (lot of reaming)
2. Cleaned intake and crossover (amazed the engine ran these were so bad)
3. Correctly routed and cleaned or replaced vacuum lines (including manifold/switchover/alda line - tested and working)
4. New air filter - took the airbox apart down to the turbo to look for obstructions - this is clear and the compressor part of the turbo spins freely with little to no play
5. New oil and filter with oil at the correct level - huge difference
6. Purged injectors
7. New fuel filters
8. added 1/2 ccw on the alda - this seems to have just added smoke - I'll probably change it back
9. Killed the EGR with a long screw to firmly seat it closed
10. Killed the ARV by plugging the vacuum

Car is starting to run well but I can't seem to get more than a couple of pounds of boost. 2 at WOT under load & 3 during the upshifts. I have several theories and I'm getting in way over my experience level with this car... thus the post... perhaps someone can help or offer a better theory...

1. Not enough O2. There is a box under the air filter (the MAF?) with a gate on the inside and electrical wires going into it. The gate swings freely and moves more than halfway with a shopvac attached to it. The turbo is probably inhaling a lot more air when properly spooled. I played with various combinations on the electrical side. Nothing seems to open this up - it looks like it just sends an electrical resistance signal at various degrees of open - possibly to a disabled emissions device??? I'm thinking of just propping the gate open to eliminate this possibility but I think it's a long shot...

2. Exhaust - the exhaust seems to work properly... good pressure at the back, but I've heard that this can get plugged and cause my problem. To test I opened that exhaust hole near the EGR and went for a drive. There was zero change/improvement but perhaps that hole is not big enough??? I figured if I got an extra pound or two I would start cutting the exhaust sections out until I solved the problem. Was this test proper? Is there a good place to loosen the exhaust to test this?

3. Turbo - Garret T3/ARV The turbo spins freely at the compressor. There are no blockages between it and the air intake. It is not gunked with oil or sludge at that end. The wastegate starts moving when I apply pressure. Full range seems to be 14-20psi or so. This should be in spec. I have two theories on this...
--A. Wastegate spring is getting weak and not completely closing the wastegate? Would it damage the diaphragm to apply vacuum and see if I can get more motion? Can the spring be replaced? Would it perhaps be simpler to sever the rod and add an adjusting linkage? Is there a built in adjustment somewhere?
--B. Wastegate itself is sludged somehow preventing full closure? Based on what the EGR did to the intake, crossover and vacuum system I'm thinking that this is not an unreasonable possibility? It looks like the turbo must be removed to clean it? I see a lot of exhaust bolts involved!! Do any of these have a tendency to break? Is there a way to get to the exhaust section easily without removing the whole thing? Any other advice on this process?

Other things that may help in diagnosis...
* Engine freely revs to just under 5000 rpm in neutral
* Car does 0-60mph in about 20s at 5280' (it was over 40 when I got it)
* Throttle linkage is missing WOT by a bit (1/4ish") at the IP. I need a helper to tackle this but it seems like it should not affect anything other than shift points (double vs single down & upshift point) and max rpm based on my understanding of the system
* I did not do a compression test but the car starts instantly and runs smoothly at all rpm levels

Thanks for any help,
Hugh

Have you cleaned and checked,your ALDA lines? thats a big step in restoring proper boost levels. If not, there are alots of threads in the forum you can access via Google questions. Just type in Mercedes ALDA and you will find a ton of stuff about it. or you can go to (y@utub#) and find stuff along with videos.
:::::how to clean ALDA boost lines.
On your engine, the nipple the feeds boost pressure the to ALDA is on the top drivers side of the intake manifold, its a little brass fitting that has a short rubber hose cominig off of it then a hard plastic line going to the fender to a little switch over protection valve, then out of the valve and onto the alda which is the (what looks like a beefy fuel pressure regulator).
If that valve is not working or if that little nipple on the intake is clogged, you will get hardly any if no boost.
you can also reroute the lines so the (possible bad valve) is taken out of the equation.
just plumb the little intake line directly to the ALDA

__________________
Live simply so others can simply live



07 E350 sport Wife's Daily
01 E320 sport My Daily
00 C230 Kompressor Our back up (new Arrival)

87 300D Turbo my Daily for 8 yrs. Selling to neighbor

82 GMC Jimmy (K5) 6.2 Diesel (my Wheeler)
73 Roadrunner 340ci My very first car, still own it

Re: Alda lines

Quick answer yes.

Long answer - when I did the glow plugs I cleaned the crossover and intake. They were sludged to the point of being nearly useless. You could eat out of them when I finished. I replaced the IM, SO and alda lines. I can put boost on the line that exits the manifold and the switchover starts venting to atmosphere at 14/15 psi. A gage at the alda reads to 14 or so psi when adding boost at the IM line. I believe this is working correctly.

I've measured boost at the IM and the Alda. They are exactly the same. 2-3psi.

Thank you.

ps - Alda seems to work - 1/2 turn ccw richened the mixture
pps - EGR screwed closed - should in theory have no more gunking

Additional Information

I found in the DIY section some info on adjusting the garret turbo for this car. (This site rocks by the way).

In any case - it looks to me as if it would be VASTLY simpler to cut a couple of inches out of the linkage and either add a slightly larger diameter tube with set screws or even something as simple as a 2 pieces of 1/4 allthread with a connector held together with some hose clamps. The benefit of this (to me) would be simplicity of adjustment as the spring continues to wear. Has anyone tried this method? Am I crazy or missing something to think this could work? Thanks

ps - I'll post some pics if I go this route

Opening the #1 manifold runner reduces exhaust back pressure but also reduces exhaust flow to the turbo. If you can stand the noise while testing, disconnect the downpipe from the turbo.

The wastegate rod should be adjustable. One thing you can do is make the rod a half turn shorter so the return spring holds the wastegate closed more tightly. While the rod is disconnected (don't lose the circlip!), check that the wastegate lever moves smoothly. What's not so easy is to check is that the wastegate flap is intact/not overly corroded and remains aligned over the wastegate port.

Here are some pictures of what's going on behind the scenes -





Sixto
87 300D^2

Sixto,

Those pics are fabulous. Thanks. Couple of questions...

1. Are you saying that I can disconnect the rod at the wastegate and turn it in (CW?) on the controller to tighten it? I believe there is a locking nut inside the diaphragm that may prevent this...

2. Should the wastegate controller move easily? I can move it only by boosting the diaphragm. I have not yet tried to disconnect it.

3. It's hard to tell from your pic... but it looks like the position of the wastegate controller rod attachment at the wastegate on your cleaned turbo is slightly closer to the diaphragm than mine. Mine is turned slightly left of perpendicular while yours looks slightly right. Based on the pic this would make a huge diff in flapper position. Perhaps this is just a spring problem.

I'll try adjusting the gate first and then I'll disconnect the downpipe from the turbo if that does not work.

4. If the problem is not the spring or exhaust I'm guessing the wastegate is gunked and not closing would be the next likely culprit?

5. How much of the turbo needs to be removed to get to that section to clean it?

Thanks for your post. I think this will help a lot.

Hugh

Those pictures are just to provide a visual. I don't think either of those are MB Diesel applications.

1) I don't know about the KKK turbo which came on some 603s but the Garrett actuator rod is threaded onto the actuator an inch or so from the actuator body. I don't see a locknut on either of my cars, just a nut to spin the rod. If necessary, gently clamp the threaded stub on the actuator then turn the rod.

2) Sounds like you have a healthy actuator or at least a healthy return spring. It takes a lot of force to move the rod by hand.

3) As mentioned, I don't think that's a MB application. All T3's are similar, though. The 603.96 application would have that image rotated 90* CCW and the wastegate flap shaft would be rotated 60* CW. The lever arm would also be oriented differently but I've lost my spatial orientation.

4) I've never seen a gunked wastegate flap. I've seen a misaligned flap.

5) It's a sucky job but I think you can remove the downpipe, remove the two brackets attaching the aft section of the turbo to the manifold, then remove the wastegate housing from the turbine section.

At the end of all this, the turbo might not be your problem. The ex-Jeremy '87 300D currently in my driveway has a recent turbo and cat courtesy of a trap recall. It didn't resolve a midrange bog in high gear. My other '87 is a bit of a slug off the line but boost is all in by 2200 rpm in any gear. The other car will run rings around this car (and leave smoke to prove it).

Sixto
87 300D^2

Sixto,

Thanks for your help so far. I disconnected the rod from the wastegate. Wastegate moved easily but did not feel like what looks like some sort of high heat gasketty type material. From the pics it looked like closing the wastegate should feel a little squishy. That was not at all the case. Was more of a metallic type close. I wired the wastegate shut. Not much difference from where the actuator put it. No real change there (maybe .1 extra to 2.1 psi). When the car cools down I'll try disconnecting the downpipe from the turbo. I'll also see if I can find that adjustment you're talking about.

Some more questions...

1. If the downpipe does not work I'm thinking the next step is to pull the turbo?
2. Or should I try removing the ALDA first (obviously simpler)?
3a. If I remove the ALDA I'm guessing I should run the line from the SO directly to the other contraption that looks exactly like it? (There is a Y from the ALDA back to that guy.)
3b. Or is it safe to just run a line from the manifold to that one?
4. What size is that clip that holds the rod to the wastegate? I pulled it with a magnet but then dropped it in my lawn.

Thanks,
Hugh

Gasket material? The wastegate flap is a thick metal disk. It's not a hermetic seal. Think manhole cover.

1) Could still be a fuel problem. Maybe even an IP timer that isn't advancing as it should.

2) I'm surprised you haven't done so already. I'm not saying take it out for good. I'm only saying take it out as a diagnostic step.

3a) The ALDA boost signal is shared by the transmission amplifier. Keep that in place or shift quality will get goofy. Just plug the ALDA line for now.

3b) You can do that.

4) Take your calipers to the wastegate flap shaft :/

Before you pull the turbo, check simpler things like the fuel tank vent and strainer.

Sixto
87 300D^2

Sixto,

Another question or three...

From your pics it looks like a properly functioning wastegate should be forced closed by exhaust gasses even if the spring tension is not pulling it back all of the way.

1. If I disconnected from the linkage would the wastegate in theory sit closed under pressure or is the spring required to seat it due to turbulence in the system?

2. If the spring is required could I wire the wastegate shut after unlinking it to test this?

3. Does this system suffer similar gunking as the crossover/intake/pressurelines/SO/ect?

Thanks,
Hugh

1) Without the actuator, exhaust pressure would blow the flap wide open.

2) You can effectively hold it shut by capping the boost signal from the compressor outlet to the actuator. That's a pretty risky thing to do. Drive the car without the ALDA first. Note, I didn't read from the beginning of this thread just now so I don't know the issue or your diagnosis history.

3) I suppose it could but it's a big honking line between the compressor outlet and the actuator. Gunk is far more likely to prevent the wastegate from opening than closing.

Sixto
87 300D^2

Sixto,

I replaced the ALDA (set back to original position) and disconnected the downpipe from the turbo. Boost immediately jumped to 6psi hitting 7 occasionally. Obviously there is some sort of blockage in the exhaust. Low end seemed to suffer with the exhaust completely disconnected (the car now has a lot of turbo lag) so I'm guessing that some backpressure from the exhaust is required for optimal performance... In any case it's a bit of a bummer as the exhaust system all the way back from the turbo looks nearly new (or at least only a few years old). On a positive note it should be easy to work on it.

Some questions:

1. Any recommendations on what to replace it with? I'm thinking of just running straight pipes back (noise isn't bad).

2. If pipe what diameter is recommended to get the right backpressure?

3. Don't know if you'd know this but it looks like at least one of the items in the system is a CAT of some sort. It does not show this on the emissions diagram on the car. I'm thinking this is what the oxtrap must have been replaced with?

4. I'm further thinking that I could replace those two devices in turn (starting with the one in the middle of the car) and only have to pipe a couple of sections?

Thanks for your help so far,
Hugh

One option is to rod the heck out of the cat. You're halfway to pulling the downpipe with it detached from the turbo. That's the easy fix if your environmental conscience and local emissions requirements don't get in the way. Replacing the cat with a straight pipe is a little more elegant.

I don't know if hearing the turbo spool down is normal. They're loud without an air cleaner so I imagine they're loud without an exhaust pipe.

7 psi isn't great. There's more going on.

Sixto
87 300D^2

Sixto,

I'm in Denver - emissions is tested for opacity only on diesels. The car last year scored <20% of allowable (I suspect it had a lot of the same issues I've been repairing - ie low boost and no signal to the ALDA to richen the mixture) . I need to do an emissions test on it before the end of this month to register it.

There are 3 pieces in the system that are not pipe. One on the downpipe (small and narrow - just a bit larger than pipe but heat shielded) one in the middle (roughly where passenger feet are) and one at the tailpipe. The two early pieces are still too hot to touch.

Assuming Benz did this (the work is very nice) which pieces would I most likely see restriction at. I was going to hook the thing back up and start drilling holes and swapping pieces with pipe until I got joy. Based on what I hear you saying - the first piece on the downpipe might be the problem?

Q's
1. What are the 3 pieces? (None are on the emissions diagram for the car.)
2. Is there any more likely than the others to be the problem?
3. What should the backpressure be (assuming I need to restrict a bit after piping the bad sections)?

Winmutt,

Once I have the exhaust sorted I'll start on the fuel issues. The linkage is close but not fulling hitting the stop. I actually caused this problem in getting the kickdown to work properly. The idle and shift points are pretty good. I've got rather lengthy instructions to hopefully get it perfect. I'll do that, the strainer and play with the ALDA again tomorrow.

ps - as a diagnostic device dq'ing the downpipe was killer. For anyone who does this I would highly recommend the following:

1. Put a small piece of pipe in place to vent the exhaust gasses out of the engine compartment. This would have been trivial.

2. Keep your test drive short (I took it about 10m - way too long).

By not doing the above I filled that section of the engine compartment with soot, damaged the oil vent line (needs replacement), destroyed the ARV line, took several years off the life of my hood liner and possibly damaged other components. Am most worried about the ATF check tube, wiring that goes into the airbox and the overboost control diaphragm. BOO!!!! (First rule is do no harm and I BROKE it.)

Thanks everyone for the help so far. This car is getting fun.

Hugh

I think #1 was answered but a counterpoint is the first item in the vertical pipe is the flex section. The second item towards the tail of the tranny is the oxidation catalyst. The last item is the muffler. Only the cat is subject to clogging. I don't think back pressure is an issue since it has a turbo. Folks have gutted the cat and/or removed the muffler. No downside other than more noise. And even that isn't a downside to some folks.

Sixto
87 300D^2