RayG

I have been given an 1985 300SD. The car looks good with a straight body and no rust evident. Approximately 200,000 miles show on the odometer. I have had the car up to approx 50 mph. It tracks straight and seems to handle well. Interior is a bit rough in spots, but mostly needs cosmetics and some small parts. All electrics other than AC and power antenna appear to work well. The car sat for approximately one year without being driven and its maintenance during the last couple of years may have been neglected somewhat by its previous owner, who was very ill for some time.

My brother-in-law (a mechanic) went over the car for me. In order to pass state inspection in Virginia, the car is going to need new brake calipers on front, upper control arms in the front, brake pads on the rear, torsion link bushings, and a drive shaft flex coupling. I can replace these parts, but it us going to cost over $600. Before I invest the money and time into this thing, I want to make sure that it is going to be worth it.

Currently the engine and transmission are working poorly. The engine has **very** little power at low rpm, but it pulls strongly above 3500 rpm. The transmission doesn't shift from 1st to 2nd until the engine reaches 4500 rpm. Even then I have to kick it up to neutral, let off off the gas, and then drop it back into drive to get it to upshift. It won't upshift to 3rd at all.

My goal at this point is to do a **minimum** level of repairs necessary to determine whether the engine and transmission are basically sound. As a first step, I have replaced the air filter and the secondary fuel filter. I will change out the the transmission and engine oils/filters as well, just to make sure things are clean inside.

Other than those very routine maintenance tasks, what should I be doing to start sorting out the engine?
Check valve lash adjustment perhaps? Fuel system troubleshooting maybe?

Can anyone recommend a good repair manual for this car?

Any help I can get will be appreciated.

Thanks in advance,
RayG

w123_w126

I recommend a purge of the injection pump and injectors. Replace the main fuel filter and do a valve adjustment. Put some algaecide into the tank, I’m afraid the fuel tank screen is clogged with algae and may need to be removed and cleaned. Change the ATF and install a new filter, that may take care of the transmission problem. If not the vacuum modulator may need to be adjusted. Remember that MB diesel transmissions shift differently than the gassers. Good luck.

Some helpful links:

http://boostnbenz.1baddsm.com/DIY/

http://dieselgiant.com/mercedes_dies...nance_tips.htm

http://www.babcox.com/editorial/ic/ic20242.htm

http://www.mercedesshop.com/shopforu...ighlight=purge

Hattaresguy

First adjust the valves every new 617 owner needs to do that. $600 into a strong running W126 is not a waste of money. As long as the compression is good and the trans doesn't slip the driveline is probably sound.

electric blue

Since you were given the car, your way ahead of the game. Lets take a look at the value of this car. I know personally because I have sold at least 5 300 SD's in my time that your car in proper working condition would not bring more then 3,500.00 to 4,500.00 on it's best day. I would have your engine and transmission checked first before anything else. Just say you need your transmission rebuilt, that alone will run way over 1000.00. How about your engine if it needs some major engine repair. What i'm saying is you can get carried away here if your not careful. GOOD LUCK!!!!!

RayG

HattaresGuy: I see you drive a vehicle called "Money Pit". That is exactly what I am trying to avoid with this vehicle. It would be a real shame not to put the car back on the road, and I just wanted to make sure that I had a good shot at getting some use out of the vehicle before spending much money on it.

After the filter changes I took it back out on the road and found that it runs significantly better. It now starts very easily. It accelerates up to 60 mph without a problem. Both are big improvements. The engine is still weaker at lower rpm than I think it should be, but I have no experience to back that up. The tranny can now be coaxed into 3rd gear by kicking it up to neutral and back, but just barely. There is no flare in the tranny when it shifts. The shifts are rather abrupt.

At this point I am going to focus on the engine, I guess a purge of the injector pump, as shown on w_123_w_126's links, should be next on the list. My fuel filter replacements were premature. At least they are cheap and simple to replace. A valve adjustment will be the next thing I need to do.

Anyone know of a source for the special wrenches required, short of going to a Mercedes dealer?

Smooooth

Sounds like you are on the right track...........

Diesel Purge - Maybe 2 cans

Check vacuum system - Put EGR into TEST mode - This may help the transmission - Get a Mighty Vac - Transmission requires proper vacuum to perform.

Start Cleaning Everything. Check any line that goes into/out of the intake manifold. Check all of the rubber vacuum connectors - Re-Seat everything.

Start using PowerService diesel additive.

Wrenches can be purchased just about anywhere - Mercedessource, BuyMBParts, Fastlane, Etc........

Once you get started and notice the little improvments that are made after each little task - you will become addicted (or obsessed)

I had to do a bunch of age reversal on my 300SDL - Original owner is 70 and never really DROVE the car.

Stephen

braverichard

RayG,

Since you stated in your original post that you really wanted to make sure the engine and transmission are in good shape before you start fixing them up to perform well, take the car to a competent Mercedes mechanic in your area and get a thorough inspection performed. It will cost anything from $100 to $150, but then once it is done you'll know if you're willing to dump the money required into it to get the car running well again. So far, you aren't even very sure of what else could be wrong on the car. While these are very durable and reliable machines, one that's neglected can be a real money pit. At this point, have you done a "poor man's compression test?" Since you said the car gets to 60mph much easier now, I'm certain the engine is good and so is the transmission. But you can't tell until you get the car thoroughly checked out, especially since you're so ahead on it right now.

After getting the car inspected and if the mechanic advises you to go on and keep it, definitely get a valve adjustment done as Hattaresguy advised, and I like the approach you've taken so far - attending to the tiny things that don't cost much. Get all the fuses in the fuse box changed out while you're at it, they don't cost much ($10 online) and can eliminate any electrical issues you may have in the car (that is, if you have any). I was totally shocked when replacing all the fuses in the fuse box of my then newly acquired '84 500SEL brought the interior front and rear dome lights, sunroof, central locking system, automatic climate control, seat belt warning light, the headlight high beam, radio and antenna back to life!! Put some fresh oil in the car, change the transmission fluid as I'm sure it was really neglected. Flush the cooling system and change the thermostat as well (make sure the new thermostat works by testing it in a pot of boiling water over the cooking stove before you put it in the car). And while you're fixing all those things wrong with the braking system, flush out the brake fluid as well.

Another piece of advice is as follows: getting a "money pit" isn't really something you can control. I've done a transmission fluid change on a transmission, saw no pieces of metal on the old fluid, didn't smell any burning on it and saw no dirt either, yet the transmission started slipping 2,000 miles later and then after that, 5,000 miles later it failed! And this was a well-maintained transmission and the old fluid was just two years / 22,000 miles old. The best you can do to avoid a money pit is to get the car inspected upfront, get its maintenance up to speed and then religiously maintain the car while being observant on issues that develop during your ownership of the car. Remember, these are 20 year-old cars no matter who manufactured or maintained them.

Good luck,

Richard

RayG

Thanks for the reply Richard. Since my first post I have had a very competent, professional mechanic and long-time 300SD owner look the car over. He gave me a list of what needs to be done to get the car to pass a state inspection and what additional work he would do if the car was his. His list was as follows:

Essential repairs:

Upper control arms in front, both sides.
Front brake calipers in front, both sides.
Brake pads all around.
Torsion arm bushings.
A few light bulbs.

Further work needed eventually:

Motor mounts.
Valve adjustment.
Drive shaft flex coupling.
Fix power antenna.
Fix AC. (Not a priority for me right now.)
Several other smaller things I don't recall. :-)

Additional things I have found:

Reupholster the front seats.
Fix short in radio / accessory circuit.

He quoted $1600 to do all of the work, more than I wanted to gamble at the start of this process. He emphasized that the engine would have to be running at its best before the transmission could be troubleshot. Putting the engine into good shape would require an unknown expense in parts and labor. That sounds too open-ended for me at this point, so I am going to do all of the simple things myself before paying for professional help.

Since I am going to be trying to troubleshoot a transmission eventually, I think I need the car to be legal to test-drive over the road, so I replaced the upper control arms last night. I am going to do brake calipers and pads tonight. I have ordered a couple cans of diesel purge, a valve cover gasket, and a set of valve adjustment wrenches online. With luck I will be able to flush the fuel system and adjust the valves within the next week. That puts me around $500 into the car at this point. If I can convince myself that the engine is running well, then I will buy a Mity-Vac and start learning about how to troubleshoot a vacuum system.

I have several more questions:

What repair manual do you recommend for this car? I have found a couple of sources for the factory manual on CDROM, but neither had any in stock. I could also find nothing in the way of generic Chiltons / Haynes manuals for this car. Any ideas?

What are the valve lash specs for this engine?

Are there any special considerations in setting the valve lash on this motor that I would not have encountered on an air-cooled VW?

I have assumed that, since this is a turbocharged engine, that the vacuum system plays relatively small role in the operation of the engine itself. Am I wrong to assume this? Do I need a Mity-Vac now?

Thanks for the help,
RayG

braverichard

Well since you've had a competent mechanic check out the car and tell you all the things it needs, and you still want to keep the car, then you're on the right track to getting it back to being a Mercedes-Benz!! Still, I strongly recommend you perform all those fluid changes I listed, particularly the transmission fluid, since the transmission isn't acting right as of now. The coolant flush is also very important, and make sure you use only M-B coolant, not that green stuff.

Anyway, to answer your questions:

1) The only repair manual I would recommend is the one we all use: the factory service manuals on CD. While those manuals don't contain instructions for everything you will ever have to do on the car, they are the most detailed, the most comprehensive, and most importantly, the most accurate and genuine! If you want I can send you a copy. Let me know via my e-mail address listed in the next paragraph.

2) The valve lash specs are contained in the service CD. If want send me your e-mail address and I will send them to you. My address is braverichard @ hotmail . com

3) No. The PDF file from the factory service manual CD I will send to you has all the instructions you need to perform the valve adjustments properly.

4) Actually, you don't necessarily need the Mity Vac to troubleshoot the engine right away. The engine operation itself isn't vacuum based, though the shut off is. I personally don't believe you have much problems with the engine. After you've performed an oil and filter change, adjusted the valves, flushed the cooling system, cleaned the fuel injectors using diesel purge, cleaned the fuel system and replaced both fuel filters, you should get your engine back to top performance. Unless of course there's an issue with your turbo not having sufficient boost resulting in low power...

Regarding your transmission, you may want to check the vacuum elements. Also, these are the diesel purge instructions I prefer: http://dieselgiant.com/mercedes_dies...nance_tips.htm

The above website has the instructions for the diesel purge process as well as for the transmission vacuum element. Both are very easy tasks. If you're able to replace brake calipers/pads/rotors and suspension components then that means you're very comfortable with going that deep in fixing cars. Good for you. That will save you a lot of money during your ownership of this car.

Good luck,

Richard

RayG

The refusal of the transmission to shift was due to the kickdown switch being stuck. After pulling it back up, the tranny now shifts. I did the essential repairs needed to pass a state inspection and the car is now legal to drive. However I have a new set of problems. I started a new thread to try to get some help with them:

https://mbworld.org/forums/s-class-w126/94871-help-elec-mech-problems-after-washing-engine-compartment.html

I would appreciate any insight you guys have.

RayG