HI yall, I'm new to the MB world and to this forum. I've always loved the look of the W123"s. that being said I just picked up a 1982 300D with 184xxx miles on the clock. I sold my wife on this by telling her how great the mileage was (I drive 500 miles a week)and we could get the kids in the back easier (i drive a 2005 subaru wrx). the car checked out good, good compression, mostly rust free ect. So long story short I had a few qustiond I/d like to ask you guys if you dont mind.

1st when driving down the hwy at 60-70 mph i get a repeating surge. Ive changed the filters but not the tank screen (to do list)
2nd A/C compressor dont switch on at all. Ive bypassed the thing-a-ma-do behind the glove box and still nothing.
3rd pass side windows dont work. Ive rebuilt the switch and tried the drivers side switch on the PS. haven't ran 12v to the window motors yet. (to do list)
Lastly like i said i drive 500 miles a week on the hwy ( I-75 in florida) and i need or should i say have to keep up with traffic (80 mph). So tach dont work, will the 617 turbo run that kind of reve or should i be looking to swap rear diffs? I know the 85 had a 2.88? Do I need to swap the whole diff or just the internals.
I know there is more but i haven't found it yet. Thanks in advance for any help yall could throw my way.

For the differential => don't swap the internals unless you know what you are doing. Best to swap the whole unit.

Electric windows => check fuses - sometimes the fuses look good but there's corrosion on the contacts

Surging - strange one - try checking + cleaning lubricating accelerator linkages. Check ALDA line between turbo and IP

AC - I can't help you there - I've never had it

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

That car should run 80 all day without any issues. The surging is a bit odd. I would check the tank screen and also check the in line filter again and see if its getting dirty. If there is only one window that isn't working then it is likely not a fuse since I think two windows are on the same fuse. I don't think you can use the drivers side switch on the passenger side because of the way the window lock is built into the switch. I would see if you can get a known good used switch. It is possible to convert the windows to manual. I'm not sure if you are interested though. I also can't help on the a/c since I never had a W123 with working air.

300D,E proper fuses

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1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."

For the surging I might consider running a can of cleaner through the injection pump. Or at least before really getting into the issue.

I have also had a few widow regulator motors go south. Just got replacements from junkyard cars when I proved them bad.

I would expect mid twenties per gallon or perhaps a little better on your commute. At sixty miles per hour although slow today will yield somewhat more I suspect.

Check your valve train lash and make sure you have good fuel pressure in the injection pump. There really is not all that much required to keep these engines in good operating condition.

These cars go back to a time where it is important to check your engine oil level. It is still a good habit even on newer cars that seemingly has gone by the wayside. Changing of the oil at reasonable intervals is also required as it becomes contaminated by soot. Especially on these older indirect injection engines. The soot dispersants wear out allowing the soot to clump. This increasing the abrasive quality of it.

There is a members recent post on the consequences of not checking the engine oil level frequently enough this past week. Any engine can spring an oil leak or it takes some time to establish normal burning and loss rates.

Sounds like the perfect car to run 500 miles a week at 80 mph.

The tach not working isn't a concern. The engine is unlikely to over-rev especially being a diesel.

I'd drive it full flat-out 80+mph if it were my car too!

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84 300D, 82 Volvo 244Gl Diesel

thanks guys for all the help and info, been out of town and wasnt able to replay. I do have one more question. On the vacuum lines that go to the motor (not the ones that go to the locks) there is a split one goes to the motor and one goes through the firewall. The one that goes into the cabin, i found just hanging there under the dash. I couldnt find where in might go. Any suggestions? I capped it.

If I remember right the vacuum line that goes thru the firewall and is under the dash should be left open.

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1982 300D

What color is this vacuum line you speak of?

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

There is supposed to be a black line that vents into the cabin. Also, there are green lines that go to the climate control unit, and yellow go to the door locks and brown go to the ignition switch.

I think you should uncap the vent.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

it a black line. it comes from the side of the VCV and T's one end goes to the 3/2 valves on top of the valve cover and the other side goes into the cabin about 1 foot and stops.

UPDATE the surging was the tank screen. It had about a 1/4 inch of gunk on it. Probably the worst tank screen i've ever seen. Put it in my ultra sonic cleaner for 8 min and good as new.. I got the ultra sonic cleaner form Harbor Fright for about 80 bucks. Now i can clean my carburetors and my wife's jewelry at the same time

............found it

http://www.benzworld.org/forums/attachments/w123-e-ce-d-cd-td/280547d1261437559-vacuum-diagram-confusion-1983-300d-300d-vacuum_shut_off-diagram.gif