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  #1  
Old 05-10-2014, 02:08 PM
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W123 300TD SLS Hard Line Leak Patch/Fix

After a couple of hours of diligent searching, I was unable to find a how-to or any thread with actual part numbers and all that jazz on how to patch a leaky section of SLS hard line on the W123 300TD. This fix will work with pretty much any section of the hard line however, may not be applicable for sections running over the rear sub-frame.

I want to preface the following with an explanation of the verbiage used in this post as there are many different names for the fittings used here. Bubble flare, double flare, inverted flare.....I use the term inverted flare because that's exactly what they are. A single flare inverted over on itself.

So, let's get started with the parts list shall we? All of the parts I used were off-the-shelf from my local Autozone and should be available at just about any parts store. You will need an inverted flaring tool as well:

1/4" x 30" standard US brake line.

The length is completely up to how far of a distance you need to span. If you have a long rotted section of hard line, you will need more.



2 x 1/4" inverted flare nuts.

This is the same nut used on standard American brake lines. Plentiful, common, and available just about anywhere. I only need 2 because the brake line came with 2



2 x 1/4" inverted flare unions

Again, off-the-shelf from Vatozone. You may have to ask them to let you behind the counter because inevitably some smartass kid will be working there and send you off down one of the aisles.



Now that we have our parts in hand, let's discuss the fix. My leak was in the supply or high pressure line so, I was able to cut the forward portion of the line at the leak, remove it from the car and flare that, along with the patch line on a work bench.

The remaining piece of the line that goes to the rear of the car wasn't as easy. Doing inverted flares on anything while on your back with the tool not supported is PITA to be sure. It took me several tries to get it. I did eventually though. Take your time lining everything up, your patience will be rewarded.

The remainder of the job was pretty straight forward, 3 more flares and put it all back together. All in all, took me about 2 hours which included a couple of cups of coffee, a cigar, and a trip to the hardware store because I couldn't find my mini tubing cutter.

Here's what I ended up with. Yes, that is hose-in-hose. PO did a crappy grease install. In the process of cleaning that up.

Moral of the story, no crazy hydraulic fittings needed. Just $20 of off the shelf parts from a chain parts store and a flaring tool.

Questions, comments or concerns...let me know.

Hope this helps someone!!





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  #2  
Old 05-10-2014, 06:05 PM
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I like your idea better as it is less Bulky but I guess you need a Flaring Kit.

Some People have used the below on Brake Lines (I am guessing in States like CA where there is no State Mandated Inspections of Vehicles) and Hydraulic Lines.

If there is room for it and the outside diameter of the Tubing is in good enough shape for the little Collars to seal on some People have used the Hydraulic Union in the Pic. It has little compression Collars that slide over the Line.
The local Autozone has them.

I have also wondered if it is not simply possible to cut the Tubing in Two and slide some Hydraulic Hose that has the internal Steel Braids and simply apply 2-4 Worm Gear type Hose Clamps on each end of the Hose. Or other types of Clamps.
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W123 300TD SLS Hard Line Leak Patch/Fix-compression-union-fitting-may-14.jpg  
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Last edited by Diesel911; 05-10-2014 at 06:19 PM.
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Old 05-10-2014, 09:17 PM
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My local autozone lent me the flaring tool, $30 deposit though. Might not be an option for those who don't have one near them.

I wondered about braided hose too. Figured I didn't want to chance having to do it again though.
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Old 05-11-2014, 01:32 AM
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Quote:
Originally Posted by curt5446 View Post
My local autozone lent me the flaring tool, $30 deposit though. Might not be an option for those who don't have one near them.

I wondered about braided hose too. Figured I didn't want to chance having to do it again though.
Oreilly Auto Parts has similar rentals. So there is a good chance other Autop Part Stores might rent out the Flaring Kit.

You won't find the Hose with the Metal Braid inpregnated into the Rubber at a local Auto Part Store.
The Have Power Steering Hose but I doubt if that goes down to 1/4" ID. I also don't know what the working pressure is on that hose and I don't know what the Working pressure is on the SLS.
It could be NAPA would have something as they are also Commercial Truck oriented.
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Old 05-11-2014, 07:44 AM
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Quote:
I also don't know what the working pressure is on that hose and I don't know what the Working pressure is on the SLS.
Judging from the type of fittings used on the flexible hose used from the pump to the hard line, I would guess the pressures are up in the 600-1000 psi range, or could be when the rear end is loaded. Although, given the way that hydraulics work that may not be the case.

My hard line had a pin hole leak at one of the rubber supports under the car. I assume water and road salt got in there and had its way with the material. When I took the support apart, I started the car to find the leak and a very small stream of SLS oil was shooting out of the pinhole. It didn't seem to be under all that much pressure but, without a gauge on anything in the system, it's all speculation.
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Old 05-11-2014, 08:20 AM
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If you bought the parts from Mercedes, they would have supplied you with straight steel line, just as you used. Pressures are far to high for a compression fitting or a hose clamp, you've used the right coupling. Nice work.
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  #7  
Old 12-08-2014, 11:36 PM
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whoa

I jumped the gun once again and just posted this question to the SLS info thread... funny how no matter how many threads I read I always miss something..

Had a pin hole in my SLS today and was wondering what size tube to buy.. I was going to repair it like a break line as described in the beginning of this thread as well!

Thanks so much for the post! Really helpful!
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Old 01-07-2016, 07:04 PM
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I finally got the rest of my SLS system healthy and my hard line sprung a leak right at a clamp grommet, dripping oil onto the diff then onto the ground. I guess the proper operating pressures were restored pushing a hole through the corroded line.

Hoping this is the last time I have to touch the SLS in a long time.

Would something like this work as a patch?
Edelmann RhinoHide 408PVF - Brake Line | O'Reilly Auto Parts

And then I would two of these?
Dorman 070650BP - Brass Inverted Flare Union | O'Reilly Auto Parts

And two nuts to meet the unions?
http://www.oreillyauto.com/site/c/detail/EDE0/121049.oap?ck=Search_inverted+flare+nut+1%21s%214_-1_5020&keyword=inverted+flare+nut+1%21s%214

And rent the flaring tool to flare the two halves of original line?
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Last edited by i_amnt; 01-07-2016 at 07:17 PM. Reason: more parts
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  #9  
Old 01-07-2016, 07:28 PM
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Quote:
Originally Posted by Diesel911 View Post
Some People have used the below on Brake Lines (I am guessing in States like CA where there is no State Mandated Inspections of Vehicles) and Hydraulic Lines.
Compression fittings are dangerous on brake lines, but I guess you can risk them on SLS lines. They're really intended for household plumbing, where the pressure doesn't exceed 30psi.
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