Got 300SD, trying to fix it up, any help would be appreciated :) - PeachParts Mercedes-Benz Forum

#1 04-14-2003, 06:53 PM

First of all, I am new to the forum. My dad just gave me his old car. It has 179,000 miles, but is a turbo diesel 300SD. Engine runs fine and turbo is brand new. Anyway I want to fix it up. It's a great older car. I have a couple problems though, and any help would be appreciated.

Problem number 1, when I turn on the car, and then turn the key to teh off position, it does not turn off, i have to pop the hood and press stop. I think its hte actual key terminal, because i can feel a lot of slack in it.

Problem number 2, the stereo does not work and mast does not go up. It appears to be stuck. Is there a way to remove the mast and put some oil on it?

Problem number 3, some of the power windows don't work.

Problem number 4, the automatic doors (all doors open when one is open) doesnt work either.

As you can see, this car needs a bit of work, but I figure with some time and effort, I can get it running well again. I would appreciate any help what-so-ever. Thank you.

pentoman · #2 04-14-2003, 07:57 PM

Firstly, this is the place to be for help with this. You might try the 'Diesel discussion' section for help with diesel specific problems (such as the switch-off).

First, you should try a search - most of these issues have probably been addressed before, and while reading search results you often learn a lot

If the Stereo does not work, it will not put the mast up. The mast is 'signalled' to go up using a 12v signal from the radio when it's switched on, and uses its own power supply to do so. Check the fuse for the radio is a good start, otherwise pull it and check the connections, and for voltage there.

For the central locking, try locking/unlocking from the passenger door, and trunk. There are actuators (i'm fairly certain, but possibly not on this early model revision) for the locking in these. If it works, the actuator in the drivers door is broken. If not, it's a fault with the central locking system itself. Not too much experience with this, try a search, but I'm pretty sure the controller is under the rear seat bench.

Which windows don't work. I believe some the switches are connected together, and I believe like: Frontright to Rearright, Frontleft to Rearleft. So, if you're rearright switch is broken or disconnected, your frontright window won't work either. May help you with any diagnoses.

All these problems may well be electrical, and a common problem with older Mercedes is corroded fuses or fusebox terminals. Before you do anything, I'd recommend replacing all fuses with new ones, and cleaning off the terminals in the box while you're at it. It's commonly done 'peace of mind' maintenance around here, and will save you headaches now and in future (I had dodgy windscreen wipers which turned out to be a corroded fuse.)

Good luck

By the way, your S-class is a 'W126'.. might prevent you getting confused

!

sixto · #3 04-14-2003, 08:37 PM

pentoman, maybe I'm slow but I didn't see anything in the original post to suggest that it's a 126 SD.

Maniac, providing the year or first few digits of the VIN will help. Heck, the shape of the headlights will help. In the US, 78-80 300SDs are W116, 81-85 300SDs are W126, 92-93 are W140. I'll guess it's not a W140

As pentoman said, everything you need to know is a search button away.

1) Could be the key, could be a bad stop valve, could be lack of vacuum.

2) As pentoman suggests, the antenna is powered by the radio. The min/max switch on the console only works when the radio is on. It only affects the final height of the antenna.

4) The doors don't all open because one is open. They should all follow the driver's door. It wasn't until 85 that they also follow the front passenger door. If it's a 116 then the locks are 'powered' by engine vacuum. If it's a 126 then the locks are powered by a dedicated pump. All the 126 SDs I've seen (not too many) have the pump wrapped in a chunk of foam beside the spare tire. I've heard that some pumps are under the rear seat.

Sixto
91 300SE
87 300SDL
83 300SD

pentoman · #4 04-15-2003, 10:38 AM

Duh.. for some reason I had it in my head he said it was an '83

#5 04-15-2003, 12:44 PM

Quote:

Originally posted by sixto
pentoman, maybe I'm slow but I didn't see anything in the original post to suggest that it's a 126 SD.

Maniac, providing the year or first few digits of the VIN will help. Heck, the shape of the headlights will help. In the US, 78-80 300SDs are W116, 81-85 300SDs are W126, 92-93 are W140. I'll guess it's not a W140

As pentoman said, everything you need to know is a search button away.

1) Could be the key, could be a bad stop valve, could be lack of vacuum.

2) As pentoman suggests, the antenna is powered by the radio. The min/max switch on the console only works when the radio is on. It only affects the final height of the antenna.

4) The doors don't all open because one is open. They should all follow the driver's door. It wasn't until 85 that they also follow the front passenger door. If it's a 116 then the locks are 'powered' by engine vacuum. If it's a 126 then the locks are powered by a dedicated pump. All the 126 SDs I've seen (not too many) have the pump wrapped in a chunk of foam beside the spare tire. I've heard that some pumps are under the rear seat.

Sixto
91 300SE
87 300SDL
83 300SD

he was right, it was an 83

Thomaspin · #6 04-15-2003, 01:42 PM

Maniac - Problem 4: your 1983 300SD uses a pump in the trunk to open and close all of the passenger door, the fuel filler flap and the trunk locks. Vacuum is supplied to these to close, air pressure to open.

The pump is triggered from a twelve volt signal generated when you open or close the driver's door with a key or by depressing/pulling the lock with the door closed. There is NO vacuum in the driver's door, unlike the later W126 bodies.

The electro-pneumatic switch (pix below) in the driver's door is fed 12 volts and switches this 12v to either the vac or pressure wires on the pump.

Two likely places to look:

1 - the pump is in the right hand trailing corner of the spare tire location. Remove the 8mm bolt and the plate it retains and you can lift out the pump in its rubber casing. Remove the pump from the casing. You will see one electrical connector with three wires (brown=ground, yellow=12v vac, blue=12v pressure) and one yellow vac tube. Disconnect both and connect a known 12v power supply to the brown and yellow wires (pump should suck) and to the brown and blue (pump should blow). In either case, putting your finger over the vac/air outlet should stop the pump in a few seconds. (That's how the pump knows the doors are locked or unlocked). If the pump is dead, get a used one from a wrecker - $85 max. These are pretty long lived devices.

2 - the electro-pneumatic switch in the driver's door. Remove the door panel (see my web site Cars - Technical - Window Regulator on how to do this) - you will also have to pull off the switch covers on the seat control switch in the driver's door. Remove the plastic moisture barrier and remove the switch - 2 8mm bolts on the lower left. When you have removed them, push down on the flat top of the moving piston in the switch - this will allow you to disengage it from the threaded post which is attached to the door knob. Push on the flat just below the concertina part in the pix below) Check for continuity between where the red/black wire (12v source) attaches and the other two (blue and yellow) - one s/b open circuit with the switch up, closed with it down, and vice versa for the other contact. If that fails, you have a faulty switch - replace for $25. Remember, get one with NO vac connector - only later W126 cars have this in the driver's door. The p/n is 002 820 5510

pentoman · #7 04-15-2003, 08:43 PM

Quote:

Originally posted by 300SDManiac
he was right, it was an 83

Weird.. must be ESP!?!