Is that vent on the side of the vacu valve still plugged? As I understand it, that is the dump hole, so unblock it.

I talked to a guy who works at the Audi division of a local Mercedes dealer. This guy talked to some of the old farts in the mercedes division, who suggested that I should replace my vac control valve. I don't see why since my vac control valve gives a nice even 10 inHg at idle no matter what. It's the output of the vac amplifier which increases. Nonetheless, the guy is getting me the part at his cost and that's what the wise mercedes old fart said to do so I will try it.
Mr Safety: the vac reservoir is an interesting theory, but when I unplugged my vac amplifier switchover valve (the solenoid before the vac amplifier) from its power supply, I stopped getting the vacuum spike, which tells me the problem must occur when the solenoid fires. Please let me know if my reasoning is off base.
Pdrayton: the hole on the side of the vcv is not blocked off, I just replaced an elbow vac fitting with a piece of vac hose stuck into the hole. The problem with my shifting predates this.
So I ordered the K-1 spring kit from fastlane since my 2-3 shift is softest. I will install it and replace fluid and filter next, then vac control valve. I will probably still have the same screwy vacuum issue after all that.
Brian: I have a replacement for what I think is the temp switch to the solenoid in question. I bought it by accident and forgot I had it. I think it's the one associated with the solenoid anyways. It is located on the driver side of the engine block, just above the injection pump. This may sound stupid, but I don't know how to figure out if this is the right sensor using a voltmeter. Do I just set it to ohms and touch the leads of the meter one to the sensor lead, one to the brown and yellow line going into the solenoid and see if they are connected?

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87 300D 162,000 miles: It's not just a car, it's an adventure!

On another thread, Dave made reference to that switch and it's in front of the thermostat housing. Yes, just set the meter to ohms (low scale) and touch one lead of the meter to the sensor leads and one to the leads over by the solenoid. There should be continuity. The switch probably grounds to the block so that the only wire going to the switch must come from the solenoid.

I seriously doubt anything is wrong with the VCV.

Brian, the temp switch that is located in the thermostat housing is one of the ones I replaced just before my shifting went all screwy. I discovered that the pin had been broken off and stuck back on with epoxy. Closer inspection revealed that the epoxy had not effectively reconnected the pin with the internals of the sensor, so the sensor had been inoperative. Therefore, replacing this sensor is what changed my shift characteristics! Before I replaced the sensor, it was as if the electrical connection to the solenoid had been disconnected.
Now the question still remains about why my vacuum spikes rather than decreases as temperature increases, but at least I know why the characteristics of my shifting changed. I think I should try testing the solenoid to see what combination of vac and manifold pressure it sends to the vac amplifier when energized and when not energized. It is written in the Steve Brotherton article referenced earlier in this thread that the vac amplifier "averages" the inputs fed to it in order to provide a vac curve that optimizes shifting under various conditions. It would be nice to know how the vac amplifier works exactly, so I could have an idea of whether the vac amplifier itself is bad or whether one of the inputs to it is screwed up via the solenoid or something else. Any ideas anyone? Exactly how does that dadgum vac amplifier decide how much vac to send to the tranny?

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87 300D 162,000 miles: It's not just a car, it's an adventure!

Nobody has really delved into the inside of the amplifier to determine exactly how it operates. It uses boost pressure and VCV output as it's variables and it also has an engine vacuum supply to allow it to function.

I have been previously looking at the wrong temperature switch. I'll have to check the temperature switch on these to see if it's dead or not. I'll bet that it is dead because disconnecting the solenoid makes no difference.

(a) I did a search on this WebSite for "vacuum amplifier" and found almost 200 "hits"... but only ~10 when I limit the search to "Title"(s)... so check out http://www.peachparts.com/shopforum/search.php?searchid=909888

(b) At: http://www.scantools.nl/info.php?cat=14&iid=74&PHPSESSID=b29c8427fb7de12659f7f7b766c1f1d9 I found that "Vacuum Amplifier" is probably more accurately named as "Vacuum Venturi Amplifier".

(c) On what appears to be a Porsche 924 FORUM I found this discussion that might be of interest: http://www.924board.org/viewtopic.php?t=13093&highlight=vacuum+amplifier

(d) Check this out: http://www.tomorrowstechnician.com/tt/tt20356.htm an article that is reportedly "Adapted from Steve Brotherton’s article in Import Car" !??

(e) And look at this very interesting short description of one type of Vacuum Venturi amplifier... at: http://www.importautoparts.com/glos_e.html , I found this:

"EGR Venturi Vacuum Amplifier - Device which uses relatively weak venturi vacuum to control a manifold vacuum signal to operate the EGR valve. Contains a check valve and relief valve which open whenever venturi vacuum signal is equal to or greater than manifold vacuum. "

(f) Apparently at: http://www.bentleypublishers.com/gallery.htm?code=VP93&galleryId=2705 this Bently service manual for the VW Passat identifies a section in the manual on how to test a vacuum amplifier on this car.

That's it for now...
Sam

I wonder if anyone can give me a part number from a parts manual or off the sensor on their car. The number I need is for the temp sensor/switch that is located right next to the thermostat. When I replaced mine I couldn't find it listed anywhere so I ordered it from the pn on the sensor. I guess it's a long shot, but maybe this sensor was not the correct one in the first place (I am not the first hack to work on this car).
Mr. Safety, thanks for the info. I now know a bit more than I did and found someone on one of those threads who can hopefully contribute to this discussion also.
Brian, I find it interesting that the sensor is rated for 50 deg C but I get my vac spike from the solenoid firing at around 80-90 deg C. Is this because the thermostat keeps the sensor from contacting the hot coolant until it opens up? At what temp does the thermostat open?
I intend to work on the car today (I have 2 kids and not much time). I will change the tranny fluid and the k-1 spring kit. I will use my mityvac to determine how the solenoid before my vac amp controls the three lines hooked to it, and to test all the inputs to the vac amp including the boost pressure line. Stay tuned for some data.

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87 300D 162,000 miles: It's not just a car, it's an adventure!

OK, I tested the solenoid with my mityvac and found out how the vac/pressure is routed to the vac amplifier. I also used my voltmeter and figured out how the temp switch circuit works. Here is a summary of what I found, I will give you the punchline at the end.

When the engine is cold (50 deg C) the temp switch located next to the thermostat is closed. This completes the circuit to the solenoid by the vac amplifier. The solenoid fires, and the boost pressure entering the bottom of the solenoid is shut off at the solenoid, while the vac from the vac control valve to the solenoid is passed through the solenoid to the vac amplifier's bottom center input. This input to the vac amp produces an elevated vacuum which softens shifts at cold engine temperatures.

When the engine is hot (over 50 deg C) the temp switch located next to the thermostat is open. This breaks the circuit to the solenoid by the vac amplifier. The solenoid is deenergized, and the boost pressure entering the bottom of the solenoid is passed through to the vac amplifier's bottom center input, while the vac from the vac control valve to the solenoid is shut off at the solenoid. This input to the vac amp produces a lesser vacuum which firms the shifts at normal operating temperature.

In short:

cold engine=closed switch=energized solenoid=increased vacuum=softer shifts.

warm engine=open switch=deenergized solenoid=decreased vacuum=harder shifts.

And now the punchline:
When a newbie doesn't know where to buy parts, he buys them online from someplace other than fastlane (I won't mention any names, but it rhymes with Autohauz, in Arizona). When a category search doesn't turn up the part he needs, he enters the pn from the part he is replacing, and buys it. Later after tormenting lots of good, helpful people on a discussion forum, he finds out he was sent the wrong freakin' switch.
I determined I had the wrong switch by hooking my ohmeter to the switch pin and my battery's negative terminal. I found the switch I had installed was open when cold, and closed when hot (the opposite of what I needed), and was also for the wrong temperature range, switching at 90 deg C.

I learned my lesson. Buy from fastlane, the forum sponsor. I ordered a K-1 spring kit from fastlane the other day and I was shocked at how fast it got here. I always had to wait 8-10 days from the other place, fastlane had it to me in like 2 days. And it's the right part
In closing, thanks and apologies to Brian, Mr. Safety, Jmana, and all who contributed to this discussion, but most especially thank you to the forum sponsor! I am going to go change my tranny fluid, filter, and K-1 kit, and nurse my wounded pride.

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87 300D 162,000 miles: It's not just a car, it's an adventure!

Good job. Everything makes perfect sense now. The switch is functioning as designed. Now that I understand the logic, I can check the function of these two. Personally, I don't really need softer shifts, even when cold. I'll bet that switch is non-functional on these.

Do you have the p/n of the proper switch?

Thanks, Brian. Yes, I have the p/n. It is 0055457024 for anyone who is interested, fastlane has it in stock from 2 different manufacturers. I just changed my K-1 spring kit and found that the short spring was broken into two pieces. This would seem a likely explanation for my somewhat softer 2-3 shift. The combination of this broken spring and the elevated vacuum I was dealing with before must be what produced the nasty 2-3 flaring I had. The broken K-1 spring was in 2 pieces and the pieces fit back together perfectly, so I don't think I have any broken spring bits floating around in the tranny. If anyone is having a 2-3 flare issue, I would recommend doing the K-1 kit. The springs must be prone to breakage.
The fluid didn't smell particularly burned and I saw no big metal flakes in the pan, just some fine metallic sludge in the pan and on the side of the filter facing the tranny. I still have to torque the pan back on, I am told to 60 in lbs. I am putting regular tranny fluid in, not synthetic. I am using the Mehle filter and gasket kit, which came with new crush washers for the torque converter and pan drain, but they appear to be too large. Anybody else had this problem? One more question: my car takes a while to go into reverse or forward. About 3 seconds or so to get into reverse. Does this mean I have a lot of wear in my transmission? I am hoping the fluid/filter change will rectify this slow engaging thing. If not is there an adjustment that helps with this problem? Modulator perhaps? Thanks again to all for the help, I have learned a lot over the last few weeks.

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87 300D 162,000 miles: It's not just a car, it's an adventure!

I just got it all back together and tested it out. My new K-1 has firmed up the 2-3 shift quite a bit. It doesn't shift quite as hard as 1-2 or 3-4 but the difference is slight. It shifts quickly and even with a little bump under hard throttle. The trans also shifts into reverse and drive a little quicker now it seems, takes about 2 seconds to go into gear instead of 3. My new temp switch is on order from our forum sponsor, that should complete the job. For now the solenoid before the vac amp is unplugged from its electrical connection. Next job is to tackle shimming my alda. I think I am running just a little lean, no wispy trails of black smoke with trans shift lever in 2 at 4000 rpm and full throttle. I am also running a bit rough at cold idle and putting out some white/grey smoke at cold idle. My glow plugs test ok with the ohmeter, so I think it's my injector nozzles....

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87 300D 162,000 miles: It's not just a car, it's an adventure!

... wacko DIYer like many of us who spend too much time on our MBZs tweaking and adjusting things to make them run like new... let me ask a question or two :

Q1 - Have you learned how to check and then adjust the IP-to-Engine timing... you know similar to the ol distributor twist on a gas engine... but here it is the entire IP that must be turned... have you done any of this yet?

Sam

Mr. Safety, I am honored to be considered a wacko MB DIYer! No, I haven't checked the IP timing, but would love to know how. The place I bought the car from specialized in used mercedes service and sales but obviously didn't know diesels. He replaced the IP when the real problem was a hole in the turbo. When he replaced the IP he managed to smash the ALDA and crack it. Soooo I wouldn't be surprised if the IP timing is off now that you mention it. I also have the stuff to adjust my valves, and a laundry list of other stuff to tackle from lubing my sunroof to changing rear diff fluid to.... Meanwhile my wife's car needs work, but I would rather send hers to the mechanic and work on the Benz Thanks for schooling and accepting a newbie.

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87 300D 162,000 miles: It's not just a car, it's an adventure!

The 603's don't wear the chain significantly if the engine was maintained with regular oil changes. It's not uncommon to go 200K and be within chain specification limits (4°).

You have no valve adjustement to perform. The engine has hydraulic lifters.

The IP is pretty easy to check. Just get the crank at top dead center, then there is a short bolt on the IP that you take out and look inside. There should be a notch visible in the hole.

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87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head