'85 300CD: will not shut off!, trans leaks over 3k rpm, odo stuck, heat always blows hot, no locks, turbo not

Question

First of all: I love this car! I bought it a week ago, after a twenty-year love affair with the W123 body style. It's from the south, so no rot, runs and rides great, and is FUN! All electrical works, great looking, all my boys drool.
Biggest problem: the day after I bought it, it wouldn't shut off after it was turned off. Pressing STOP is ok when it's August, but it's getting cold, and will get old fast. Where to start?
Next biggest: trans leak. It leaked almost a quart on a day trip yesterday, all expwy@70/75, 21mpg. I decided today to try staying @60 or under - not one drop! And 30.7mpg! I dropped the trans pan, replaced filter, and topped off with AMSOil ATP. It doesn't look wet anywhere but pan gasket and lower, can't see where it could be leaking from when heavy accel.
Next: odo froze@164k. Speedo works fine.
Next: even in the blue range, heat is HOT!
Next: driver door key goes in lock, but lock will not turn.; pass lock turns, but won't lock.
Last: doggy - no turbo?

Answer 1

Aw. That stinks.

If you don't get a good answer on here, try asking the mechanics at askautopro.com . It's free and they seem to know everything.

I hope this helps!

Answer 2

I have forgotten more than most people know about these older MB deisels so lets look at one problem at a time.

Not shutting down. This usually has two solutions. The high idle is adjusted all the way to the high setting and the adjuster is broken and/or the shut-down lever on the injector pump is stuck due to wear. The cable to the shut-down lever is also mounted at the pump with a rubber bushing which could be broken off which will allow the cable housing to move and not let the cable move the shutdown lever on the pump.

Trans fluid useage vs leakage. There is a modulator valve on these that is vacuum operated. When running at higher speeds there is more pressure buildup inside the transmission. There is a pressure releif vavle that is mounted on the top of the transmission. If this is plugged the pressure will sometimes push through the diaphram of the modulator valve. Pull the vacuum line on the modulator valve to see if there is any transfluid on the inside of the line. If there is replace the modulator valve and clean the pressure releif vavle. If not, then there may be a very small leak at the rear output seal. You can tell this if there is a wet spot directly above the seal on the floor pan where the fluid has be slung. Good move to go to the Amsoil for the trans. Amsoil also has an excellent deisel motor oil that I strongly would recommend. They also make a bypass oil filter that will clean the oil of almost all the diesel carbon particles suspended in the oil for longer engine life. They also have a prestart preluber system that will bring the bearing oil pressure up to normal pressure before you start the engine thus saving on bearing wear as well.

The answer above on the Speedo is one of the best "self fixes" I have read in a long time. HOWEVER, to in any way, shape or form tamper (read repair) with a speedo/odometer is illegal in all 50 states unless you are licensed repair shop. It is best to go to a auto parts recycling place like Pick&Pull here in California and get a used one and have a licensed shop repair that one asking that the mileage be set to the mileage on your car. Most will accomdate that request.

Interior heat control. You probably have a stuck coolant control valve for the heater. For this I would strongly recommend getting a manual and follow the troubleshooting section for the HVAC system. Sorry but there are so many different spots to look at that it would not fit here.

Door locks. Does your car have power door locks? I cannot remember if they were standard by then or not. Just a rambling thought -- sorry. Anyway, the standard locks usually wear out the mechanisms after this long. You will either need to get donar locks from the "pick&pull" or new ones from MB (expensive) full set including the truck lock runs about $400 (last time I bought a full set) If your car has vacuum powered door lock (only kind MB had at that time) then each segment will have to be inspected individually and repaired a necessary. Again, parts will be expensive.

Doggy -- Not knowing the history of the car it is difficult to say. At the odometer indicated mileage a good tune-up should be considered. Adjusting the valves and setting the timing of the fuel injection pump will be a start. Replacing the injectors, changing all fuel filters and just for ducks while you are in this part of the process of restoring the the car to good running condition, change the glow plugs too. Have the mechanic run a compression test at this time too. These will at least rule out the ussual problems of "doggyness". After that there is not much else to do except to look at the turbo. The '85 300CD was a turbo in the States. During that period, and I do not remember exactly what ones it was on, but MB had a particulate trap on the exhaust of all of their US bound deisels. I honestly can't remember if it started in '85 or not, Again you will have to refer to the manual for info on the exhaust. If indeed it has a "P-trap" then it could be partially plugged. I know there was a recall on the "P-traps" and MB was replacing them at no charge. The another possibility is the wastegate is stuck open and you are not receiving full boost from the turbo. If that is the case, replacing the entire turbo may have to be done since the wastegate vavle is part of the turbohousing and many times rusts open or partially open.

Hope this helps.

Answer 3

You have a lot going on with this car. But you are right. The 123 series is a fine vehicle. I still miss my 240D. That said, I can help with the odometer problem. When I fixed mine I was so proud that i documented the process. I wish I could remember what I did to fix the "turn off " problem. Re: odo - here goes:
Step one: Put a moderate German wine in the bucket to chill. It is a little early to do so, but once your hands are greasy, it would not do to handle the bottle. I prefer a leibfraumilch. Mechanic's choice.

Step 2: The instrument cluster was pressed in, held in place by a rubber gasket. I pressed it out by hand front to back, working around the areas I could reach, and easing it a little at a time. Once the panel was loose, I carefully detached the lines and hoses to the instruments. The oil pressure gauge was a direct reading of the pressure, so there was pressurized oil in the line. It did leak and I had a rag there to sop it up. The speedometer cable was (surprisingly) hand tight. I labeled all the wires and lines, but I am thorough that way.
The speedometer was held into the instrument cluster by three screws in the back. I removed the screws. At this point I held the speedometer in my hand. I couldn't believe that I was supposed to reach around all those metal plates to get to the odometer gears, so I killed a half hour trying to remove the speed indicator needle and nearly broke the speedometer. Fortunately, I stopped in time. I cannot recommend pulling on the speed indicator needle. It was a bad move on my part.

The speedometer cable drove a gear which drove an idler gear which drove the 1/10 of a mile indicator. The 1/10 of a mile indicator had gear teeth on one side, with which to be driven and a single extrusion on the other side with which to drive the "one mile" indicator one tenth of a turn each time it rotated a full turn. The 1/10 of a mile indicator was supposed to be attached to the metal shaft. It was not, so it was able to spin free. It was necessary to attach the 1/10 of a mile indicator to the shaft.

I was only able ot remove the shaft from the 100,000 mile indicator side of the odometer. The shaft had a gear pressed into the least significant digit side. The 100,000 mile side had a air of pressed extrusions which prevented the shaft from being removed.
It looked like this: +=======! .

I ground the ears off the shaft with a Dremmel tool. I then removed the shaft by slowly pulling the shaft through the mounting holes. I removed each mileage indicator with a pair of tweezers, and kept them in order because I was too lazy to look and see if they were all the same or if one was different. I then used a scratch awl to knurl the shaft in the area where the 1/10 of a mile indicator would be when the odometer was reassembled. I could have used glue, but that would not have been elegant. And, after all, this was a Mercedes. The knurlings were about 1/8th of an inch long. I then inserted the shaft into the hole of the support bracket, slid the 1/10 of a mile indicator most of the way down the shaft but (and this is important) did not press it onto the knurled part of the shaft. To do so would have forced the far end of the shaft into a position where the other gears could not be pressed on. Using the tweezers, I put the remaining indicators on. The indicators were put on the shaft oriented to read the proper mileage. The last indicator was put partially on the shaft, the shaft then aligned with the mounting hole in the 'far' bracket,
then as the gear side was pushed toward its seat, the 1/10 of a mile indicator was pressed onto the knurled portion of the shaft.

Let's talk about knurling a minute. The knurling takes place through the horizontal axis and consists of parallel straight lines. The pressing and dragging of the awl creates a slight valley in the metal, at the same time raising a thin sliver of metal above the former surface level. This is not meant to remove metal, simply to move it around a little. I used six lines. It didn't take much.

Once the shaft and indicators were in place, I put a brass washer over the end of the shaft, a handy #2-56 nut I had in my kultch box, and used Silicon Seal (Liquid Iron, RTV, hell, epoxy would do) to hold the nut in place. I left the nut about 1/1000 th of an inch from the washer. Not rubbing, but not a big gap either. This is a non critical dimension. Let it dry, then reassemble the dash. It would pay to have a fresh rag when reattaching the oil pressure gauge. Also, under no circumstances should the engine be cranked or run while the oil pressure line is unattached. Pressures from a diesel could be dangerous.

Step 3: Drive the car around the block. If the odometer turns, you have just saved yourself approximately $800. Park the car. Pull the cork. Raise a toast to John Foley, the man who taught me how to do this.

Answer 4

This car has a vacuum shut off valve. Very common problem easy fix. Its on the injection pump.
If the trans leaks it would do it at any speed you got me on that one.
The odometer is gear driven off the speedo so it sounds like you broke a tooth. Find a speedo shop to fix it.
Heat is hot what does that mean?
Drivers door lock could be broken again somewhat common. Door handle needs to be replaced. On the passenger side does it lock with out the key? This side use a vacuum module that has a rod going to the door handle so it could be the rod came off or the vacuum element is bad
If the turbo goes on that car you would see smoke out the back. Some 85 cars had California emissions on them called a trap this will suck power if clogged. For this one find a shop that knows that car and have them look it over.

Answer 5

Mine leaks trans fluid out of the speedo cable seal,some times as it is parked,but will not leak during a drive, you mite check your cable seal too.

Answer 6

i could replenish my dogs's swimming pool with chilly water and take a seat it out interior the nice and comfy sunlight for a pair of hours to get warmed up. Bless your heart hun. possibly boil some water on the range in case you like warm water. i'm sorry you lost your warm water. :(

Answer 7

Check out this web site that's devouted to mercedes diesels.It might be able to help.Ive been reading it the past few days and found numerous things to fix mine

http://dieselgiant.com/mercedes_diesel_maintenance_tips.htm

Good luck on getting your classic back on the road soon.

Answer 8

I wasn't sure if you were serious!
Your almost 22 year old car needs some major work. Hope you didn't pay much for it.

Answer 9

all i can say is good luck mate