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  #1  
Old 04-24-2010, 12:17 AM
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Question 1985 300D - Fishtailing like crazy

Hello Everyone,

My '85 300D has been fishtailing like crazy. It's been this way since I bought it a few weeks ago. If I go over potholes, rough patches of road, manhole covers, basically any kind of bump, and the rear of the car starts to slide out to the side of the road.

I've been able to deal with it by going slowly over bumpy areas and avoiding bumps as much as possible, but it's really not good. Sometimes you can't help but hit them and I need to be able to control the car. It seems to happen at speeds above 40mph...not too noticeable below that.

When I'm going over bumps there is a loud knocking sound coming from the rear. Sounds like something is knocking back and forth.

I also have 3-4 inches of play in the steering wheel that I've been tightening using the adjustment bolt on the steering box. The front end tie rods and control arms are in decent shape.

The fishtailing combined with loose steering is a problem I need to address ASAP.

I think the problem may be related to the suspension. The front passengers side spring is dead and bows inward. The front driver side is also dead. There is no spring when I push down on the front end. It's riding very low up front.

On the other hand, if I push down on the rear of the car it really bounces around.

I'm thinking I may need new shocks and springs all around. But perhaps something else is going on....???

Has anyone experienced this before?
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'85 Euro 300D - 258k 4 spd manual
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  #2  
Old 04-24-2010, 12:45 AM
whunter's Avatar
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Answer

Quote:
Originally Posted by Ya Mar View Post
Hello Everyone,

My '85 300D has been fishtailing like crazy. It's been this way since I bought it a few weeks ago. If I go over potholes, rough patches of road, manhole covers, basically any kind of bump, and the rear of the car starts to slide out to the side of the road.

I've been able to deal with it by going slowly over bumpy areas and avoiding bumps as much as possible, but it's really not good. Sometimes you can't help but hit them and I need to be able to control the car. It seems to happen at speeds above 40mph...not too noticeable below that.

When I'm going over bumps there is a loud knocking sound coming from the rear. Sounds like something is knocking back and forth.

I also have 3-4 inches of play in the steering wheel that I've been tightening using the adjustment bolt on the steering box. The front end tie rods and control arms are in decent shape.

The fishtailing combined with loose steering is a problem I need to address ASAP.

I think the problem may be related to the suspension. The front passengers side spring is dead and bows inward. The front driver side is also dead. There is no spring when I push down on the front end. It's riding very low up front.

On the other hand, if I push down on the rear of the car it really bounces around.

I'm thinking I may need new shocks and springs all around. But perhaps something else is going on....???

Has anyone experienced this before?
Yes, many times.

Here is a basic list of what you should need:

* A good used steering gearbox
* 4 Shocks
* 4 Springs + shims + a compressor to install them
* Differential mount

You may also need these parts:

* Idler arm repair kit
* Upper control arms
* Lower ball joints
* Lower control arm bushings
* Rear sub-frame mounts
* Trailing arm bushings
* Rear sway bar links
* Engine mounts



Have a great day.
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  #3  
Old 04-24-2010, 01:20 AM
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Join Date: Dec 2007
Posts: 3,607
in other words, a LOT of work. you might consider selling the car and looking for a better example. once upon a time, I fell in love with a diesel benz and ended up plowing around $15K into it. the body was rusted to begin with so it never paid out. better to cut and run and look for a car in better condition. suspension repair is costly and tedious.
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  #4  
Old 04-24-2010, 01:32 AM
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Location: Nashville, TN
Posts: 1,530
But you don't have to fix all that at once. Start with the shocks and springs or whatever the most likely problem is. As long as its safe it doesn't have to be perfect. Soundl like you have a lot of good components still . Suspension stuff can be a pain but its cheaper than a lot of things and once you do it you're good for a 150,000 miles. I bet 500.00 in parts or less , you do labor, will fix you right up.
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  #5  
Old 04-24-2010, 06:20 AM
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I think that the list above covers it all really!

however, Most of those items may be perfectly fine, and just one or two are causing the problem. Broken springs are a good possibility and easy to spot...

Best bet would be just to check and test as many of those points as is possible.

Play and excess movement in ball-joints and bushes is reasonably easy to spot, and as your issue is SO bad, the faulty parts should stand out like a sore thumb!

I'm betting that the shocks on the rear are pretty toasted and or their bushes.
--Bottom ball-joints can cause wandering at speed on good flat roads, bushes on TCA can cause Horrible tyre wear. Steering knuckles can cause all sorts of vague steering feelings and clunks and the idler bush can cause some odd knocking noises when rocking steering...

Rear trailing arm bushes are pretty solid, but at 25 odd years old should be given a careful check...

Steering-box may have some wear, but careful adjustment can improve things no end--I had a steering on one W123 so 'loose', you could turn steering-wheel 6" before anything happened, Careful adjustement brought this right down and transformed the car!--Saved a HUGE packet too!

(Adjustment is on the top of steering-box, Large lock-nut, 19mm? and Allen key 7mm? Screw Allen-bolt Outwards to reduce the the amount of play, and settle for a 'loose movement' at the edge of the steering-wheel of about 1/2 inch, with NO tightness, do adjustment with wheels in dead ahead position and without engine running....)
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W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....
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  #6  
Old 04-24-2010, 06:37 AM
layback40's Avatar
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Location: Victoria Australia - down under!!
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X2 with Alastair !!
The steering box is a bit of a trap if you dont know to adjust it the opposite direction to most steering boxes.
Other problems tend to be very obvious when you look under the car. Some front end places will do an inspection very cheap & then try & get you to sign up for a lot of unnecessary stuff. Maybe worth getting an inspection done for say $20 if you can & then posting the report on here, wait for people on here to comment before getting any repairs done.
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1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving
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  #7  
Old 04-24-2010, 06:53 AM
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Location: Rochester, NY
Posts: 180
Agree with the above...DON'T sell it or put it out to "pasture"...we'all wanna see these cars on the road. I just did most of what was mentioned above throughout my suspension and the parts aren't all that expensive if you shop carefully. IMO springs & shocks are first on the list. rear sway bar links are easy and cheap. Front end is a PITA so I'd do that all at once and also check the steering damper while you're in there. The force of the forum will help you!
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  #8  
Old 04-24-2010, 12:14 PM
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Join Date: Apr 2010
Location: Vermont
Posts: 187
Hello All,

I think the existing steering box is okay for now. I've tightened it up with the 19mm wrench and 6mm allen wrench. Replacing it is not on top of my priority list.

Regarding the suspension, it's my thinking that new shocks and springs on all 4 will go a long ways towards improving the handling. But I think there is something loose with the suspension in the rear. The knocking/deep rattling sound I referred to in my original post....I'm still not exactly sure what the cause of this sound is, but hopefully when I put in new shocks and springs I will discover the source of it and fix it at that time.

I agree it may be a good idea to take it to shop to get an estimate of everything that needs to be replaced in the back so I don't go replacing parts that are just fine. However, almost everything on the car is 25 years old, so it wouldn't hurt to upgrade the rear suspension with all new components...I suppose it's just a matter of how much I want to spend.

One of the reasons I like this car so much is because it's a 4-speed. I could probably find a w123 from out west that doesn't have rust and is better condition all around and swap transmissions...but that seems like an even bigger project than fixing what I have...

I also need to address significant rust damage on the car, so before I get too invested with mechanical repairs, I need to figure out how much the rust repairs will set me back.

Anyways, Thanks for the comments!
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  #9  
Old 04-24-2010, 12:35 PM
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Location: Kona, Hi
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It sounds like the rear is either losing touch with the ground (worn out dampers) and/or there are bad bushings causing bump induced steering. This effectively would mean that the thrust angle and/or toe is changing with the shock of a bump.

All of this can be fixed with new (or used) parts. This of course is the beauty of putting as little $$ into this car as possible and search for a cleaner example and keep the first car as a parts donor.

Keep in mind that sinking a ton of money into an old rusty benz may not pay in the end. Not that we do this as an "investment", but what I mean is that starting with a better car will improve your experience over the length of your ownership. For what ever reason we as a group play with these cars, not because we have to, but for some other unexplainable reason.

I recently purchased an older SD and decided it needed too much work to improve it as a driver. It is now relegated to parts car status.

My search for a clean car with minor needs continues. I may have found a good clean example. I have started a thread asking for info about it.

best of luck. What ever you decide, these are great cars and in any condition, worthy of our time.
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  #10  
Old 04-24-2010, 04:12 PM
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Hmmm

Quote:
Originally Posted by Ya Mar View Post
Hello All,

I think the existing steering box is OK for now. I've tightened it up with the 19mm wrench and 6mm allen wrench. Replacing it is not on top of my priority list.

Regarding the suspension, it's my thinking that new shocks and springs on all 4 will go a long ways toward improving the handling. But I think there is something loose with the suspension in the rear. The knocking/deep rattling sound I referred to in my original post....I'm still not exactly sure what the cause of this sound is, but hopefully when I put in new shocks and springs I will discover the source of it and fix it at that time.

I agree it may be a good idea to take it to shop to get an estimate of everything that needs to be replaced in the back so I don't go replacing parts that are just fine. However, almost everything on the car is 25 years old, so it wouldn't hurt to upgrade the rear suspension with all new components...I suppose it's just a matter of how much I want to spend.

One of the reasons I like this car so much is because it's a 4-speed. I could probably find a w123 from out west that doesn't have rust and is better condition all around and swap transmissions...but that seems like an even bigger project than fixing what I have...

I also need to address significant rust damage on the car, so before I get too invested with mechanical repairs, I need to figure out how much the rust repairs will set me back.

Anyways, Thanks for the comments!
Here is the short list of what you should need:

* 4 Shocks
* 4 Springs + shims + a compressor to install them
* Differential mount
* Rear sway bar links = these make massive noise/rattle when bad.

I disagree on repairing the rust, swapping the transmission into a perfect body is two days work for the average DIY.

Even if you swap the engine the job should only take two weekends.
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  #11  
Old 04-24-2010, 04:33 PM
b2948kevin's Avatar
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Join Date: Oct 2008
Location: Reno, NV
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You may be right... You'll just have to get a new one. Good news is that I'll take it off your hands for you
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  #12  
Old 04-24-2010, 07:57 PM
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Location: Sterling, VA.
Posts: 286
most difinitely take it to a shop and get it checked. make sure that you are really capable of doing any repairs to your suspension before you start buying parts and ripping it apart. i'd say unless you have a good friend with tools and skill to help you with this kind of stuff, let the shop fit it. a decent shop will not try to hammer you into buying everything under the sun and will prioritise which repairs should be done RIGHT NOW, and which can wait or are easily performed at home. and do not forget to get an alignment when the repairs are completed. this is a safety issue, and you can make your problems worse if you don't know what your doing. by the way, a coil spring can kill you if you don't know what your doing and you try to remove it.
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