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Garage => Mechanicals => Topic started by: rich@jinxy.com on 07 June 2019, 11:29 PM

Title: 1974 350SE Power steering high pressure hose
Post by: rich@jinxy.com on 07 June 2019, 11:29 PM
Hello all,

I have an Australian 1974 350SE and need a replacement power steering hose. Turns out there are a whole heap of different options for these things and I've even come up short using the EPC!

I've had a look through the posts here and can't find anything to help so I'm putting it out there to everyone in case we can come up with a part number? I've attached a picture.

Thanks
(http://power steering hose.jpg)
Rich
Title: Re: 1974 350SE Power steering high pressure hose
Post by: TJ 450 on 08 June 2019, 01:04 AM
I can’t help with the part number unfortunately.

You could have this remanufactured at Pirtek or other specialist.

I had my 6.9’s one done with the correct type of hose locally not long ago.

Tim
Title: Re: 1974 350SE Power steering high pressure hose
Post by: rich@jinxy.com on 08 June 2019, 01:09 AM
Thanks Tim. It's good to have options. I may end up doing that!

Rich
Title: Re: 1974 350SE Power steering high pressure hose
Post by: Alec300SD on 08 June 2019, 01:18 AM
It looks like part number 109-997-45-82 which appears to be NLA.
If your fittings are good, the rubber hose itself should be able to replaced.
Unscrew it clockwise (left-handed thread) from the fitting after removing the cone shaped portion.
Install a new rubber hose, either from  a hydraulic supply house, or by trimming one from the longer 116-997-69-82 high pressure hose.

I swapped out the steering box end on a used 116-997-69-82 hose.
This modified hose was used to bypass the transmission oil cooler while the radiator was removed to be re-cored.
Title: Re: 1974 350SE Power steering high pressure hose
Post by: rich@jinxy.com on 08 June 2019, 01:49 AM
Thanks for the potential part number and the idea of re-use. Unfortunately one of the fittings is badly chewed up ... so I can't use it. However I will see what I can do to separate the hose out anyway just to learn a little something and at least free up the "good end".

Great getting feedback. Thanks guys.

Rich

Title: Re: 1974 350SE Power steering high pressure hose
Post by: rumb on 08 June 2019, 05:09 AM
Get yourself a pair of curved vice grip as shown here:
https://mercedessource.com/store/self-leveling-suspension-sls-high-pressure-hose-replacement-kit-w-instructions

PM me your email and I will send you the instructions. - there are to large to upload here.
Title: Re: 1974 350SE Power steering high pressure hose
Post by: rich@jinxy.com on 16 June 2019, 08:13 PM
A big shout out to *rumb* who has now "steered" me right for future hose work. Sorry about the pun. In the end I called into my local Hydraulic (Motohose - Hydraulink Shire) place and they fabricated me up a new one for less than $100 AUD on the spot so I couldn't argue with that. The first image is of the new hose.

The second image is of a spare set I received with the replacement power steering box. I've looked at EPC and again I can't find a good match to fathom the correct part numbers so I can post them up for sale to another enthusiast with the same problem but different hose specifications.

If anyone happens to know which iteration these are from then please go ahead and post a comment. There seem to be multiple designs depending on country of sale as well as LHD/RHD considerations. There are even certain types which are within a VIN range as far as I can tell.

Thanks all for the responses. Very helpful!

Cheers

Rich




Title: Re: 1974 350SE Power steering high pressure hose
Post by: raueda1 on 17 June 2019, 05:30 PM
Hi,

Hope this isn't a thread hijack, topic is the same - power steering hose.  I'm just now doing the same job as the OP on my 6.9.  Fortunately the fittings were OK and could be reused.  I was able to locally find what I thought was a suitable substitute, Gates SAE 100R16 (ISO 11237).  This is a high pressure hydraulic hose with 2 steel reinforcement braids and rated at 8000psi.  The OE hose only seems to have one braid and power steering hoses seem to be typically rated at 1500psi so I'm wildly over spec.  So far, so good.

[Sidebar comment:  The old hose was a replacement that somebody did at some point.  Unfortunately the old hose wasn't well marked so I don't know what is was except for being  "MSHA 2G11C."  That's just a flame retardancy rating for mining applications so it doesn't help much.]

Here's my concern. This new hose is only rated for 100°C. Modern power steering hoses seem to generally be rated for 150°C.  Obviously the 6.9 engine is large, hot, and the exhaust manifold is pretty close to the hose.  Nevertheless, under-the-hood temperatures have increased a lot since the mid-70's and higher temperature materials are now far more widely available.  Anybody know what the temperature or ISO spec was on the 6.9 hose (or any of these older power steering hoses)?  This would be super helpful in helping others find suitable hose.  Thanks,

[EDIT:  Correction.  I noticed that the hose itself does NOT come particularly close to the exhaust manifold.  The section of the assembly that gets close is steel tubing.  I surmise that the MB engineers recognized that no rubber construction would survive that much heat.]
Title: Re: 1974 350SE Power steering high pressure hose
Post by: TJ 450 on 18 June 2019, 02:10 AM
The original hose has a rubber sheathing protecting it, and it also has a restrictor built in closer to the pump end (6.9). I’m not sure on the spec but it would be DIN or Metric, not SAE.

Tim
Title: Re: 1974 350SE Power steering high pressure hose
Post by: raueda1 on 18 June 2019, 09:59 AM
The original hose has a rubber sheathing protecting it, and it also has a restrictor built in closer to the pump end (6.9). I’m not sure on the spec but it would be DIN or Metric, not SAE.

Tim
It would be great for all of us to know exactly what the high pressure PS hose spec was.  Finding the right hose for DIY replacement can be a challenge.  My hose was replaced at some point and it's not at all clear that it was the right hose.  I actually suspect it wasn't.  Fortunately the same fittings are in fine shape.  There's no apparent restriction though. :-\

Anyway, in general DIN/ISO specs have an SAE counterpart and vice versa, so that's not an issue for us.  The burning question is, what did MB spec in the 70's?  Nobody seems to know.  I've tried to search but no luck.  What we do know is that now the temperature spec for "high temperature power steering hose" is 150°C/300°F (SAE J2050).  The corresponding euro ISO spec seems to be ISO 11425:2018 Type 5, though max temp rating is only 135°C.  SAE J2050 dates back to 1991 which was after the great under-the-hood temperature rise seen during the 80s. 

My guess is that contemporary power steering hose is overspec'd for temperature for our old cars.  If so then the task of finding a replacement is much easier.  Bulk, high pressure power steering hose (SAE J2050 or ISO 11425) isn't easy to find at a retail level.  However, 100°C bulk hose is readily available (used for construction equipment etc), and for much higher pressures than the automotive stuff.

So, I'm going to quit guessing and get some hard data.  When my car is back on the road I'm going to measure temperatures under the hood and on the PS components.  If the fittings on the high pressure side don't go over 100°C then our lives become easier.  Stay tuned.
Title: Re: 1974 350SE Power steering high pressure hose
Post by: raueda1 on 27 June 2019, 06:59 PM
The original hose has a rubber sheathing protecting it, and it also has a restrictor built in closer to the pump end (6.9). I’m not sure on the spec but it would be DIN or Metric, not SAE.

Tim
It would be great for all of us to know exactly what the high pressure PS hose spec was.  Finding the right hose for DIY replacement can be a challenge.  My hose was replaced at some point and it's not at all clear that it was the right hose.  I actually suspect it wasn't.  Fortunately the same fittings are in fine shape.  There's no apparent restriction though. :-\

Anyway, in general DIN/ISO specs have an SAE counterpart and vice versa, so that's not an issue for us.  The burning question is, what did MB spec in the 70's?  Nobody seems to know.  I've tried to search but no luck.  What we do know is that now the temperature spec for "high temperature power steering hose" is 150°C/300°F (SAE J2050).  The corresponding euro ISO spec seems to be ISO 11425:2018 Type 5, though max temp rating is only 135°C.  SAE J2050 dates back to 1991 which was after the great under-the-hood temperature rise seen during the 80s. 

My guess is that contemporary power steering hose is overspec'd for temperature for our old cars.  If so then the task of finding a replacement is much easier.  Bulk, high pressure power steering hose (SAE J2050 or ISO 11425) isn't easy to find at a retail level.  However, 100°C bulk hose is readily available (used for construction equipment etc), and for much higher pressures than the automotive stuff.

So, I'm going to quit guessing and get some hard data.  When my car is back on the road I'm going to measure temperatures under the hood and on the PS components.  If the fittings on the high pressure side don't go over 100°C then our lives become easier. Stay tuned.
I'm happy to report that our lives became easier.  After a test run under high temperature conditions* I measured the temp of the power steering box, hose and fittings using one of those IR thermometer guns.  Basically everything was about 180°F., which is great.  I'm going out on a limb and assuming that the 6.9 runs hotter under the hood than most other models.  This means that high pressure hydraulic hose rated at 212°F/100°C will be just fine.  Such hose is much easier to find than the 300°F/150°C stuff used for modern power steering hose.  Let's all get hosed!  ;D

*steady 85mph up a long, high altitude grade (+2000m) with A/C on and 86°F outside.  I'd venture that in the real world most of us won't see much worse than this.