The steel fuel lines and the rear brake line that go between the rear subframe and the car body are seriously rusted on my '85 300D. I have patched the leaks in the fuel lines but that brake line needs replacing. Here is my plan: Remove the entire subframe/trailing arm assembly with the rear differential as a unit. I could then replace the rear brake line and the fuel lines properly with new steel (and new fuel rubber hoses). With all this assembly out of the way, I'll replace the subframe mounts, trailing arm bushings, differential mount, transmission mount, and driveshaft wear components (front and rear flex disks, center support and bearing, and "dust" boot). I'll also pull the fuel strainer from the tank to ensure it's clean.

So hear is the big question:
Can I remove the whole assembly by disconnecting everything (subframe, differential mount, brake lines, driveshaft, emergency brake, shocks and sway bar) and then just slowly jack up the car body on both sides until the springs are fully extended?

Tim

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'85 300D 276,000 mi

Most here will agree as there have been many posts about MB springs. In a search, you will find that all will suggest a coil spring compressor designed for MB's. They can be rented from ************************, ***************, and I believe one of the forum members, check the stickys at the top, has one to rent.

It may sound ideal but if anything shifts during jacking you may be seriously injured. It is just not worth the risk.

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Sam

84 300SD 350K+ miles ( Blue Belle )

You probably could get it apart, and MAYBE do it without hurting yourself. BUT I'm not to sure you will be able to get the assembly back together, if something shifts, Then realigning everything to get the trailing arm bushings to attach could be difficult, an then your stuck. So get the compressor and do it safely.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

You can buy a hydraulic spring compressor (item no. 47890-ocbh) from the Harbor Freight catalog (1-800-423-2567) for $100 or a mechanical one (03980-scbh) for $12. Granted these are not Proto tools but then again how many times will you use the.

It sounds like a royal PITA but you probably could do it that way. But, you would have to jack the body at four points. If you tried to just jack the back end, the spring would take quite a bend in it as the body moved up and forward.

Why not just rent a compressor? Two of us have them in the tools for rent. See the sticky on the first page.

If you use the compressor, the brake lines and sway bar can remain in place.

If you want to replace the springs while you're in there, support the back of the car and carefully cut them with a torch. Lots of big bangs and sparks, but it's not as dangerous as it sounds.

When you buy the new springs get a spring shop to compress and band them for you. Once everything is back in place and you have the weight back on the springs cut the bands and away you go. They can band them straight or with a curve, whatever makes them easier to install.

The only thing to worry about is if the bands break on the compressed springs while you are handling them. It's only happened to me once.

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Dropout

1978 240D work in progress

Have you tried the hydraulic spring compressor? Not sure it would work due to spacing of the springs.

I know the mechanical one you mentioned will not. In fact, on one of these threads, someone shows the "timebomb" of using that type of spring compressor. Very, very dangerous.

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Sam

84 300SD 350K+ miles ( Blue Belle )

First of all, there's no reason to lower everything at once on the rear end, even if you had incredible hulk-like muscles that could handle it. The differential alone without the axles weighs about 70 pounds. It's extremely easy to spin out the two 8 mm bolts that hold the axles in the hubs, pull the trailing arms only, then the diff with the axles attached to it.
Second of all, the mercedes shop manual has directions for lowering the arms, springs attached, without a compressor. I just did an entire front end rebuild without a spring compressor, and it was no big deal. The only tricky part is keeping everything steady while you jack the trailing arm back up into place. The rear springs especially have very little compression on them when the trailing arm is down on its stop after jacking the car, you can actually squeeze them a little with your fingers, not nearly as heavy as the front springs.
Third of all, before I started my front end rebuild, I bought one of the more popular spring compressors, as recommeded here. It broke. I'm not naming the brand because I'm sure it was just a defect, but since I lived through the experience I've decided not to spend much time around that kind of stored energy. Even the name brand compressors run a risk, I personally prefer the springs with as little pressure as possible on them. Letting my front end out was only about 3 inches after disconnecting the UCA. Good luck!

You need to rent the proper spring compressor. Taking short cuts never pays off.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I agree with those who say get the proper compressor & use it. I rebuilt the front end of a TR-4 with a jack (only) when I was younger & stupider, and almost lost a finger when a homemade compressor came apart on a Cadillac spring. Pay the money & keep your body parts.

I have an update since I started this thread. I knew that the condition of my brake line was suspect where it goes between the subframe and the car body and needed attention soon. I just didn't realize how soon. It developed a leak Saturday in my own driveway, just before I was about to take it out for a drive. (I'm sure glad it didn't happen to my daughter while on a busy road.) I did a temporary fix yesterday. I bought 25' of 3/16" steel brake line and a metric bubble flare tool. I replaced the full 130" section but ran the line below the subframe instead of above it, where it belongs. I now need to drop the subframe and finish the job properly.

I have been examining the job of removal of the subframe along with the trailing arms and differential without a spring compressor. I am now of the opinion that it is not only doable safely, I think removing the whole assembly (without a spring compressor) is the SAFEST way to do the job if done correctly. That is the way I plan on proceeding. I'll let you now how I make out and whether doing the job changes my opinion.

Tim

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'85 300D 276,000 mi

With the shocks removed, the springs act on the body and the subframe.

You are attempting to separate the subframe from the body.

You must first suppport the body and then you must carefully support the subframe when you unbolt it from the body, otherwise the springs are going to attempt to send it to China. If you happen to be between China and the subframe, we might not speak again.

Please don't argue that the safest way to do the job is without a spring compressor. We might think you have lost your mind.

Knock-knock: "Is you da widdah Scull?"
Ms. Scull: "Heavens no!"
Knock-knock: "The hell you ain't!"

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Never a dull moment at Berry Hill Farm.

Randy, Would this be a good time to share your ' hand pinned to the floor' story ?

I would but the swelling hasn't gone down enough yet to let me type that much.

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Never a dull moment at Berry Hill Farm.