PS / SLS reservoir seeping from top cap...

[Thresher]

The power steering / SLS reservoir on my car has developed a tendency to seep from the top cap and I am looking for ideas/recommendations/suggestions.

With the car parked in my garage on a flat surface, I can check the reservoir fluid level and it is below the max line. If I start the car and let it idle for a while; essentially the time it takes to run a diagnostic scan; I notice that fluid is seeping from the cap on the reservoir. I wouldn't characterize it as gushing, but seeping. Alternatively, I can wipe the reservoir clean, drive the car about 10 minutes away and check the reservoir and it still is mostly clean -- definitely not seeping as much as when the car is idle in the garage, but some fluid has come out.

The basic problem then seems to be that the rate of fluid entering the reservoir is faster than the rate at which the fluid is removed; thus too much fluid rises to the top and then begins to seep from the cap which as far as I can tell is designed to allow fluid to escape in this situation.

The reservoir does contain a filter, which could be getting clogged and is certainly suspect in this case. As some may know, the reservoir for cars like mine with SLS is NLA from BMW but recently I did manage to source a used SLS reservoir from an Ebay seller in the UK. The filter inside the replacement reservoir isn't perfect, but may very well be better than what I have. In terms of what I do next, I think installing the replacement reservoir makes sense and would allow for inspection of the filter on the current reservoir; but are there other parts of the system that could be faulty? All flexible PS/SLS hoses in the engine bay have been replaced within the last few years; but I guess there still could be a hose problem...

While this has been going on, I've also been dealing with other intermittent power steering issues; I've had fault codes for an open and short circuit with the servotronic. Recently I had my mechanic replace the servotronic with a new one, and I even swapped the power steering pump. The other intermittent power steering issues and fault codes are now gone, but the seeping issue persists.

The car drives and steers nice. The rear suspension seems harsher than it should be; barring any leaking on the rear struts, the SLS accumulators could possibly be due for replacement; I'm also not clear how the fluid lines to/from the accumulators may affect the fluid level in the reservoir.

Any suggestions are appreciated...

[Thresher]

I'm also not clear how the fluid lines to/from the accumulators may affect the fluid level in the reservoir.

After studying the info on realoem, and having to deal with a failed PS system on my E36, I came up with the following diagram to show the hydraulic oil flow through the system for my E38:

E38-PS-SLS-oil-flow.jpg

I'm still chasing the issue with oil seeping from the reservoir cap; but now I understand better the two inputs and one output at the reservoir. Next steps seem to be to inspect hoses at the reservoir for a tight fit and I should drain the reservoir and inspect the filter. That later option is much more viable now; At the time of my initial post I was low on spare fluid and I had noticed that the price of new CHF 11S oil has risen to $42 at my local Autozone while some online places were about half that. Now that I have a multiple liters of new fluid at an affordable price, I will definitely drain the reservoir and compare the filter to the filter in the spare used reservoir that I have.

[Thresher]

This adventure in repairs on my car can now be closed. Final solution was getting the LUK LFR68 pump rebuilt by Jay Stratton up in Santa Ana, California.

Initially the cause of the seepage from the top of the reservoir wasn't clear. Upon inspection, the fluid level in the reservoir looked fine -- it wasn't overflowing. I had thought that perhaps the screen was blocked, and perhaps that affected the rate of drainage from the reservoir. With a good bit of luck and perseverance, I did manage to locate and acquire a gently used SLS reservoir from a seller on Ebay for less than $50 + shipping (that was a bargain for an item almost as rare as a unicorn). There was certainly some gunk in the reservoir when it was pulled from my car and inspected. The original reservoir had no cracks, which was also a good thing. The replacement reservoir went into my car last month, and my original reservoir is now in my spare parts collection. I did confirm that air was getting into the system; after driving the car for a while, I parked and immediately checked the reservoir, there I saw numerous small bubbles, dissipating very quickly. That was an 'ah-ha' moment, as previously I was a bit slower in checking the reservoir and didn't catch the bubbles before they were gone. Now it was no longer a reservoir drainage issue, but an air leak issue.

20221217_152215.jpg

More checking of the hoses was done, and along the way I spotted a good price deal on the rear accumulators from FCP, so I had those installed. Finally my mechanic and I came to the conclusion that the pump is faulty. I sourced a spare LUK LFR68 from Ebay advertised to be in good working condition, and in reality that pump had similar issues as well.

A review of the options to get the LFR-68 pump rebuilt or replaced by a re manufactured one showed that in the US, Jay has his repair service (Jay's BMW Parts), and then there are Cardone, Maval, and BBB Industries. Probably there are others, but that is who I came across. I saw some other brands listed on autodoc.co.uk, but other brands in the European market were out-of-stock.

I opted for Jay's repair service and so far so good.

One thing I learned through this experience, is that work on the SLS components is getting harder. The pump is NLA, so tracking down a spare LFR68, while possible, doesn't always get you a problem free pump. The SLS pressure hose from the pump to the rear of the car is now NLA from BMW. Anyone thinking that they need to replace that hose should immediately look on Ebay where I have seen a couple of eastern European sellers still offering that hose.

I also realized I need to have a plan in place in case the day comes and the SLS system can't be repaired any longer. That is a bit daunting, as for my car with EDC+SLS, that means swapping to a non-EDC shock absorber setup from Bilstein and probably replacing the LFR-68 with a single vane pump to avoid looping the SLS hydraulic circuit (yes, I know that can be done, but Jay and I realized the internal workings of the LFR68 could have been better designed; so my goal would be to get what is perceived as a better designed, single vane pump).

[CPHES]

Try this guy - he has posted on some other forums here ( e23 ). I’ve not dealt with him, but stuff looks ok.

https://www.jaysbmwparts.com/work/power-steering-pumps.

I also ran across a place in Poland - but you need a core.

[Thresher]

Try this guy - he has posted on some other forums here ( e23 ). I’ve not dealt with him, but stuff looks ok.

https://www.jaysbmwparts.com/work/power-steering-pumps.

I also ran across a place in Poland - but you need a core.

That is the guy I used to repair the pump in my car.

[a777fan]

Thanks for posting about this. I’ve noticed the same kind of seeping on my lid.

Pretty unfortunate that the filter isn’t replaceable on its own. Quite a poor design choice IMHO.

[Thresher]

Thanks for posting about this. I’ve noticed the same kind of seeping on my lid.

Pretty unfortunate that the filter isn’t replaceable on its own. Quite a poor design choice IMHO.

From what I can tell, the white plastic filter must be press-fit into some recess within the reservoir. The white "tabs" in the picture I posted can be used to spin the filter 360+ degrees in either direction. When the reservoir is removed from the car, hoses disconnected and turned upside down, you could insert an object like a dowel and possibly knock out the filter. However, the hole in the bottom of the reservoir that would be used is slightly off center from the white filter piece, so any pressure applied wouldn't be centered and that may or may not be an issue. I was worried about the age of the plastic and it possibly shattering. Neither my mechanic or I attempted that, as we didn't want to risk ruining a reservoir that isn't easily replaced (even with me having a spare one...).

But, these days with 3d-printing, perhaps someone could come up with a replacement filter that would function with a mesh screen? Unfortunately, there doesn't seem to be any alternatives in the aftermarket for a replacement SLS reservoir for the E38.