General 300D Questions - PeachParts Mercedes-Benz Forum

Ara T. · #1 09-16-2004, 10:07 PM

Hello everyone. I'm new to this forum. Glad I stumbled onto this forum! A ton of information to be had. Actually im pretty new to my 1985 300D Turbo (it's got a bit over 193,000 miles) as well. I'm 17 and have been driving it for almost 5 months. I love the car to death, and get made fun of 'cause I wash it so much

I love the sound of the engine as it revs up to 3-4K RPM.. hehe. Anyways, I have some general questions about the car. Please forgive my noobishness

1.) I've driven my sister's 98 Corolla and my Dad's '00 Accord... and I noticed the power steering is a LOT smoother (a lot less resistance) than that of my 300D... now, I know it's dumb to compare these cars, but my car makes pretty wide turns... to get into a parking spot I have to maneuver it like a bigrig. As in, if the space is to my left, I'll have to bear right a bit and then begin my left turn into the parking spot so I get in nice and straight and make the correct angle. Is this normal for these cars

2.) How much does this car weigh? I've heard a lot of different things, ranging from 3500-4000 lbs.

3.) Vacuum! It seems this is a major annoyance on these cars. I know I've a problem because the car suffers from:
a.) Sluggish locks.
b.) Sometimes the engine keeps running with the ignition off.
c.) Harsh shifts, especially when the engine is cold.

I know for sure this is because of a vacuum leak somewhere, but what about breaks? I got the brakes changed a couple months (they're new, not even a 1000 miles on the brakes) and it takes a lot more braking to stop the car then, say, my dad's Accord (again, sorry for the comparison). Especially downhill, there's a lot of brake pedal travel to get the car to stop (thank god for engine breaking!) Are the brakes supposed to be like this for these cars? Or is this relatable to the vacuum leak?

One more question... the car leans kind of a lot when I take (90 degree) turns at like 15-20 mph. It's not just the 90 degree turns, small curves in the roads get the body leaning too... is this because of the shocks? Or some other part of the suspension? Is this what they refer to when I see shops selling "comfort" shocks? Would "heavy duty" ones solve this problem? Ok, that's all I can think of... thanks to anyone in advance, and I commend you if you read all of that.

Hatterasguy · #2 09-16-2004, 10:14 PM

Welcome to the forum, my friend's poked fun at my SDL last year in highschool a little. Until I showed their Honda's couldn't hold a candle to it on the highway.

First the steering on your car is better than most, MB made the steering as more of a power assist(sp?) system and it is not like the highly bosted systems on American and Japanese cars.

You have a vacum leak, get a vacum tester from an autoparts store, mitty vac I think their called and start hunting. Also do a search all of those problems are very common.

Ara T. · #3 09-16-2004, 10:18 PM

My mom has an 86 300SDL... cool car man. That things like a friggin limo

The extra cylinder makes it a lot smoother to drive too.

Hatterasguy · #4 09-16-2004, 10:24 PM

Yeah their a big car, I really like long wheel base S class Mercs.

I want a long wheels base W140 when I get out of school.

tangofox007 · #5 09-16-2004, 10:58 PM

Sounds like you have a brake problem. My 300D will stop in a much shorter distance than most vehicles, especially considering that it is a pretty heavy car. The brake problem could be related to the vacuum problem. If the pedal were hard to push, might suggest a vacuum or boost problem. But if your door locks work at all, you probably have adequate vacuum when the engine is running. I would try bleeding the brakes as my first step in resolving the poor braking issue. As for the vacuum leaks, start by checking all of the rubber connectors in the engine compartment. Then you can isolate particular door locks by plugging the vacuum lines under the front passenger carpet. Often the door lock actuators will leak because of the old rubber. I would skip buying a vacuum tester until I had made a good visual inspection for loose or cracked components. Then listen for leaks immediately after you shut the engine down. Fixing the vacuum leak will likely solve the hard shifting problem. The hard steering could be the result of the steering gear box being adjusted too tight. It adjusts backwards from most American cars. CCW to tighten, CW for a looser fit.

Ara T. · #6 09-16-2004, 11:30 PM

Hmm.. pardon my ignorance but where do I tighten this steering box?

(thanks for the replies)

I did search, but found most people had loose adjustments, odd. Still couldn't find the location of the box though. I'll look tomorrow after school.

tangofox007 · #7 09-17-2004, 05:43 PM

The steering gear box is located in the engine compartment, left side. Following the power steering hoses. That's where they go from the p/s pump. There is an allen head bolt on the top of the gear box with a hex lock nut. Loosen the lock nut. The adjusting bolt tightens the gear when turned counterclockwise. Turning it clockwise loosens the fit. If it is too loose, the steering wheel will have lots of play or lost motion. If it is too tight, steering will be hard. And excessive wear will occur to the mechanism. (Make sure to hold the adjusting bolt when you tighten the locking nut.) Most American cars adjust exactly opposite. So it is common that people try adjust the gearbox and make things tighter when they are attempting to do the opposite. (Don't expect that you will be able to adjust out all of the play.) Also you might want to change your power steering fluid and filter. The filter is in the bottom of the reservoir, under the spring. You might want to purchase a Haynes MB Diesel 123 manual. Many chain auto parts stores carry them. They have lots of pictures and cover many of the more routine maintenance and service procedures. (But the Haynes manual does not mention the power steering pump filter.)

Ara T. · #8 09-17-2004, 06:22 PM

I appreciate the help, tango.

dieseldiehard · #9 09-17-2004, 06:37 PM

tangofox007 dscribed the process perfectly. I have had to replace the steering boxes on two of my W123's - after they get worn there is no amount of adjustment that will help reduce the slop. That said, there is nothing like a tight steering box in these cars. Any slop makes it feel lllike the car is a road hog, and side winds will cause the car to lurch suddenly - all the forces related to driving and steering and so on meet at the steering box.
re: leaning in curves - W123 all do

That is part of the softness yet strength that the MB 123 suspension system carries, and many drivers hold these as desirable characteristics.
Buy a W124 if you want a sedan that hugs the road in curves. Do NOT try heavy duty shocks, unless you are planning on hauling a heavy load most of the time and you can put up with bone jarring response to chuck holes and the like. I had a set on my '83 and I had to take them off and go back to comfort shoicks, Bilsteins, the only ones to use BTW.

JimSmith · #10 09-17-2004, 08:26 PM

Aar T.,

First, the steering in your car is designed "heavy" compared to other, lighter Japanese cars, and the typical American land yacht of the same era. If it is too heavy the problem is most likely underinflated tires or underinflated oversized tires, as this could also explain the lean you feel. These cars are a little tippy going into a turn, but they take a set and body lean does not continue as the turn gets tighter at the initial rate. It takes some getting used to, but after a while you learn to drive them without being alarmed. I would be very surprised to see the steering box over tight. If you hear no particular noises from the steering system, then I would not jump to a box adjustment or a fluid change. Some of the other steering issues you are noting are a lack of familiarity and willingness to push the wheel around hard enough. These cars have excellent turning circles (very tight for their wheelbase), and I would be surprised if the Honda or Toyota you cited have tighter turning circles, or faster steering. They are just light to the touch and therefore seem more agile. Once you get used to making the effort to turn the wheel at the rate you want to, you will find these cars to be very easy to park and get through tight spaces.

These cars also have superior braking systems. So if your brakes are not impressive, you have a problem. Either in the vacuum pump or the vacuum system, or in the braking system. Without additional data it is not feasible to offer any better advice than to find a competent mechanic and get your brakes attended to. If the travel of the pedal is not about an inch or two max, after which the pedal gets good and stiff and the brakes respond strongly, you probably need more than to just get the air out of the system, but that is a good place to start.

Good luck! Jim

Hatterasguy · #11 09-17-2004, 08:32 PM

My SDL can out turn my Camry with no problem. It is a much better car to swing around in tight places. Mercedes seem to have extremly tight turning circles.

rickjordan · #12 09-17-2004, 08:42 PM

Ara T. The W123 series sedan weights about 3700 lbs. That's "curb weight" which is a full tank of fuel and all it's fluids. My '83 300TD weights 3850. To find out exactly how much your car weights, look on th edriver's door jam. You will see the letters GVWR, this is the weight of the car and the max laod it can caryy. On the same data plate you will see the max weight, subtract the 2 and there you have it, you car's weight. My TD weights a bit more because it's a wagon.

psfred · #13 09-17-2004, 08:45 PM

All Mercedes are very nimble. I can turn my old 220D (W115 chassis) around in a city street just by turning in a circle. If you are having trouble turning tightly enough, check the power steering fluid, it's probably low. Effort is a bit higher than US cars for sure, but not THAT high. If you are working hard to park, you don't have power assist for some reason (bad belt, bad pump, etc).

I strongly recommend the MitiVac hand pump. Not really cheap, but it's got a vac guage on in, wihtout which you are not gonna get things working correctly.

The excess body lean is missing rear sway bar links and or bad bushings up front the clonking noise going over bumps will go away when these are replace. Rears are easy so long as you have a safe way to jack the car up and remove the wheel (This means jack stands, DO NOT work on a car with the wheel off and only a tire chaning jack holding it up!). The bolt to the end of the sway bar and the wheel carrier, should be fairly obvious when you pull the rear wheel.

I suspect you have either air in the brake lines or stuck calipers (fairly common on older MBs as there is some sort of compulsion to skimp or rotors, resulting in jammed pistons).

If you aren't going to do this yourself (or rope a significant other into the job), find a good independent mechanic to fix the brakes -- you should be able to knock the passengers head on the dashboard in a panic stop, the cars have EXCELLENT brakes, much better than Japanese. Do not go to any generic brake and muffler shops, the screw then up terribly.

It's also possible you have a bad vac pump and hence low boost, but I doubt it, more likely lots of vac leaks.

Peter

Ara T. · #14 09-18-2004, 12:18 AM

I checked the power steering fluid... under the threading that the cap screws onto is the plastic cylinder thing with an arrow pointing downward, which I guess is to indicate how much fluid to add... if this is the case, the fluid is low.

ktlimq · #15 09-18-2004, 12:33 AM

Ara T.,

What is the feeling of return?
I mean the steering return when you exit corner.

Does it return slowlier than Honda?

Mine returns slowlier than several US and Japanese brand cars. I am not sure whether mine had problem or MB's are designed so.