1992 400e Steering Gearbox Leak from Top Input Seal

[PDX]

Hello,
This is my first post here, and I wanted to start off by saying thank you for all the information presented on this forum, it is priceless. I'll provide more of an introduction once I get some photos, but I'm in Portland Oregon, and have a 1992 400e with approximately 145K (purchased from another member of this forum). I am in love with this car, and I commute to/from work in the 400e every day (40 miles or so).


In chasing down a power steering fluid leak, I have replaced the reservoir short hose, the S-hose, the gearbox lower seal/o-ring, but I still have a few drips of P/S fluid showing up on the garage floor. To the best of my ability, I've diagnosed the leak to the power steering gearbox top (input) seal through careful cleaning and visual inspection.


-Has anyone here known this input seal to go bad? I can't imagine the leak is coming from anywhere else, because all the hoses/pump/lower shaft seal are dry.
-Does there happen to be existing info regarding this job? I was unable to locate existing info.
-If I do move forward with gearbox R&R, are there any pitfalls to watch for? (I know the part about measuring the pitman arm distance)
-I'm presuming I have to R&R the gearbox to re-seal (upper seal, not the lower seal)?
-Can anyone help with part number(s) for this re-seal (it seems the Mercedes online parts catalog now costs $75/year)


Based on the difficulty of R&R of the gearbox, I may just live with the occasional drips, however, I don't really want to replace the LCA again as the other leaks I had caused degradation of the rubber bushings. The left LCA is now new, and I had the factory alignment performed (by MBI here in Portland)


I welcome you thoughts and opinions.

Thanks a ton!
-Mike

 

[gsxr]

Mike,

I have never personally seen the input shaft seal leak on these steering boxes. 99% of the time it is the output shaft seal. The FSM shows how to fix this but it requires totally disassembling the steering box - not for the faint of heart. If you aren't comfortable with that option, I'd consider either a used steering box (re-seal the output side proactively, easy/cheap, click here for a detailed thread) or looking into a rebuilt / reman box, if the prices are tolerable (I have no idea, haven't checked).

Related question - what PS fluid are you using? ATF, aftermarket fluid, or OE/dealer? If it's not OE, I'd consider draining / flushing the system and using the OE gold/yellow fluid. If there is no change in the leak, I would next consider trying about 1 ounce (yes, 1 oz, VERY little, less than they recommend) of either Blue Devil or ATP AT-205 stop leak. See if that cures it. Those are the last options before pulling the gearbox for repair/replacement. Both are "seal sweller" products that should not damage any other parts of the system when used in small amounts. I generally don't recommend that type of fix, but for an input shaft seal... ugh...

 

[gsxr]

Oh btw, welcome to the forum!

 

[PDX]

Excellent, thank you for the reply. My impression was that nobody really ever replaced the input shaft seal, but wanted to verify.

I failed to mention that I use the OEM MB P/S fluid, and it appears the previous owner did as well.

I'm comfortable with R&R of the box, but tearing it all apart might push my limits. I'll try the seal-sweller and see if that helps. For the effort, I may just live with some drips.

Thanks again, and I'm glad to be here!
-Mike

 

[PDX]

As a follow-up, I added approximately 1/4 bottle of the blue devil "seal sweller" product suggested above and it worked very well. I still have an occasional drip of fluid, but no longer need to top up the reservoir on a regular basis. Thank you very much for the recommendation!

 

[nocfn]

PDX I had red stuff in my C126 and the box was going and always wet. In 2013 I flushed and went with MB spec, and my leaking stopped. Only last month did the box finally get too sloppy and I replaced it. Chicken or the egg, but I think running the spec fluid matters.

 

[M104-AMG]

<SNIP>

Related question - what PS fluid are you using? ATF, aftermarket fluid, or OE/dealer? If it's not OE, I'd consider draining / flushing the system and using the OE gold/yellow fluid. If there is no change in the leak, I would next consider trying about 1 ounce (yes, 1 oz, VERY little, less than they recommend) of either Blue Devil or ATP AT-205 stop leak. See if that cures it. Those are the last options before pulling the gearbox for repair/replacement. Both are "seal sweller" products that should not damage any other parts of the system when used in small amounts. I generally don't recommend that type of fix, but for an input shaft seal... ugh...

Anyone successfully use Liqui Moly's Power Steering Oil Leak Stop ? Only gets a 60% rating vs. Blue Devil (66% ) and ATP AT-205 (71%) . . .

neil

https://www.amazon.com/Liquimoly-20284-Power-Steering-fluid_ounces/dp/B07B58BPTK

 

[nocfn]

Bunging up the tandem pump is never an option for me. Fix the leak properly, it isn't hard to do.

 

[Ascension]

Bunging up the tandem pump is never an option for me. Fix the leak properly, it isn't hard to do.

a 420 doesn't have SLS so its a single stage pump. Still properly fixing the leak is the only way to do it right.