300DT Questions and Travelogue

I've been lurking on this group for some time and have finally bought a 1983 300D Turbo. After spending years on the alt.harley newsgroups it has been refreshing to wander around here and experience the degree
of civility and tolerance you seem to afford each other. There is quite a tale about how I came to my MB, which will follow, but I wanted to get the questions up front so if you chose to skip the travelogue you might be willing to answer some questions anyway.
-High speed (at 80-100 mph) rhythmic vibration. If I were to draw it, it would be like a sine wave. Will get the tires balanced. Any other ideas?
-Is it just me, or does eBay seem about the best place to get parts online?
-There is a strange vacuum sound after the engine turns over. At first I thought it was starter run-on. Anyone deal with this?
-Are parts really that different between certain chassis? For instance, the front turn signal lens for the 126 looks just like the one for my 123.
-I bought the Haynes manual for this beast (they were great for my Brit Motorcycle period) but there's nothing in there in the way of a vacuum schematic. Is there one available on line or otherwise without buying the MB manual?
I've been doing my own car work since I was a kid and have Harleys I tinker with. Figured it'd be great to get a MB diesel as a "rolling project" since they seem to be a very DIY type car – and I can fit in ‘em comfortably (6'4", 230lbs.). Now, in the great PNW the bio-diesel folks have put a rather large demand on anything diesel and car-ish which has driven up their price. So, I contacted my dad in Tucson, AZ and asked if he'd look there. He called with a 1983 300D Turbo for $1500. I asked him to have a look and take it to a shop if it was at all promising. A few hours later he calls, "I bought it."     "Did you take it to the shop?"     "Uh, no."     Silence.     "I got it for $1,100."     So, I now own a car 1500 miles away that could be total junk. We find a shop in Tucson that other locals praised: Craig's Auto Repair. So, I have him bring it to them and I call ‘em and say, "You have $1000 to get me back to Oregon."     So, I synced up my having to deliver a '91 Toyota Cressida to San Luis Obisbo with picking up my new/old MB in AZ. Not to be obnoxious, but I dislike a lot of Japanese engineering. This car was designed for people my wife's size: 5'2" and 100 lbs. Also, what genius decided to have the controls on BOTH sides of the steering wheel? Even my old Dodge van has the cruise, wipers, and high beams on the turn signal stock – damned handy when eating while driving. I got about two hours into the drive before I had to remove my wallet from my back pocket. The seats, quite frankly, suck.     So, I drop this Toyota in CA and hop a plane for Tucson. The next day I see my new car. We go into a shop with no less than 7 golden retrievers in various states of excitability running around and there's my car up on the lift. The first thing I see when I look up at it is a wheel well vividly infected with rust. The front and rear passenger tails lights are toast due to the rather painful dents next to them and the paint matching from the last dent-fest looked like it was done by a four year-old. When it came off the lift I could see the sunroof had an acne of rust and the interior was missing more than a few pieces.     Shit.     The good news is that only had 144k on it and mechanically, it wasn't too bad. The shop replaced all the glow plugs, fuel filters, primer pump, did an oil change, air filter, upper and lower control arm bushings, radiator cap, and stabilizer bar link, and a million little things – all for about $1100.     I hit I-10 at 5 a.m. toward Phoenix. She was surging like crazy. She'd sputter, catch, run up to 80 mph, them cut out and stumble back down. Now, they told me the injector pump was fine so I made my way into the left lane and ran it up to 90 mph (with the rest of the rush hour traffic) she sputtered for about 10 miles then cleared up, never to do that again.     The Mojave was a merciful 75 degrees, but I was dealing with a 30-40 mph cross/headwind. The cruise lever had been broken off (already won one on eBay for $10) so I took the monopod from my camera and used it as a hand-throttle to rest my leg. Crossed what was perhaps the most boring drive of my life between 80-100 mph. No sputtering, but an intermittent vibration (that wasn't bad enough to slow me down). Seemed to get about 22 mpg crossing the desert. Slowed way down for the rest of the drive into Sacramento. Mileage went up to almost 30 mpg when keeping it between 65-80 mph. 950 miles that day. I tell you, those MB seats are the bee's knees – especially after dealing with tiny Japanese seats. Almost 1000 MB miles and I never had to take my wallet out of my back pocket except to buy fuel and coffee.     In Sacramento I borrowed my sister-in-law's garage to jack it up and spin the wheels and check for bent rims or loose bearings. Negative on both. Did use a pint of oil – and I think most of that came from the leaky main seal.     The next 550 miles home was through the mountain passes. It did really well holding it's speed up the hills, but really had a struggle if I had to clamp on the binders when some bozo decided to block the left lane going up hill. Trying to gain speed going uphill was a chore. Never got to try her out on the snow and am not sorry.     She did great the whole trip. Think I'll keep her. So, now begins the search for parts. Thanks for getting this far in the tale. My initiation to MB ownership was a trial by fire. The car passed and we have bonded. I'll be posting with questions from time to time and hope someday to be answering a few. Craig's Auto Repair in Tucson, AZ gets big points for doing what needed to be done and telling me honestly what could wait until I got to my own garage.
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You had a good initiation. Too bad about the rust, now that you know what these old M-Bs are about you can find a good one and then sell this rusted one.
Vibration: Tires, driveshaft flex joints or motor mounts, in that order of likely hood and cost to fix.
Manual: Try to buy a real M-B paper manual on e-bay. The Haynes manual tries to cover too many models and will leave you high and dry in the midst of a repair job.
Vacuum sound is a vacuum leak. Engine's vacuum pump is on its front end, it's obviously OK. That leaves the vacuum plumbing system and hopefully not, the brake booster, which isn't cheap.
There's another possibility for that noise. The turbo engines have a fuel enrichment system that adds fuel to the engine during acceleration. At the aft end of the intake manifold is a "banjo fitting" (clean it out) that transmits the turbo's boost pressure over to the injection pump. Mid way the plastic line has an electric "switchover" valve that's located on the firewall in front of the driver. The hoses to this valve sometimes leak and so could be the source of the sound.
Incidentally, while we're at this system and you're a DIY guy, let me tell you how it works. On the top of the intake manifold is a boost pressure sensor. It's wired to the switchover valve. The purpose is to prevent a run away engine; the switchover valve will open at 16 psi turbo boost to protect the engine. The reason that's necessary is that the turbo's boost pressure is piped to the ALDA, a couple of sealed metal bellows in the top of the injection pump. As the pressure increases these bellows contract and through some levers this motion moves the fuel rack toward more fuel. Without the 16 psi limit and a stuck shut turbo wastegate (set to open at 11 psi) the boost could cause ever higher fuel amounts and a run away engine.
Some "experts" will suggest you "adjust" the ALDA for more performance. Don't it's factory set for best performance vs. least smoke. If the bellows get broken they cannot be purchased OTC but come only from Bosch.
So for good performance from this 120 HP, 170 ft lbs of torque engine keep the air filter clean, the "banjo fitting" clean and check the connections to the switchover valve for leaks. Change to oil every 5K miles and buy decent #2 diesel and this engine will run well. Adjust the valves (cold) every 15K miles. That's it!
P.S. Diesel drivers KNOW it won't accelerate on hills; they just plan ahead - CHARGE!
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Have cked everything suggested and all is well. The car runs great. A little rough for the first 30 seconds when started in the morning but after that she sings. Have gotten the hang of driving it and wish it had a way to keep it into 2nd gear. I live at the bottom of a hill and 1st is too low and when in "S" it makes its way into 3rd which dogs it way down. My wife compained of the diesel smell. After I degreased to engine it cut it down about 90%. The eingine didn't look that dirty to me, but I guess it was. Besides German Star, eBay seems to be a good place to find parts online(if you know how to play the eBay game. Lots of crap out there ...). Was WAY lucky to buy a car three states away and end up loving it! Thanks for your input and advice!
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