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In flushing the ABC to remove any aberrant fluid or old dark fluid (as Gary is finding when bleeding the struts), is it possible to use a vacuum brake-type bleeder to further remove the fluid remaining in the struts and accumulators? Will the negative pressure cause any issue with strut or accumulator integrity?
 

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cyglee,

That is an interesting thought. I can't wait to hear the response from some of the guys/gals who are a LOT more knowledgable about this system than I am. IF it will work, I'll certainly have a stab at it!!

At first 'blush', it seems a system that is built to withstand 3,000 psi hydraulic pressure internally SHOULD be able to withstand less than 16 psi externally (as I recall, typical atmospheric pressure at sea level is 15.4 psi).
 

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Discussion Starter #26 (Edited)
Its not that simple or possible for many reason...

for one, the system operates under almost 200 bar, that's a tad less than 3000psi... AKA upper limit of pressure washers range... I would love to see a vacuum pump that would beat that kind of pressure...

For two, the system is not designed to withstand vacuum, in terms of valves position, open closure sequence, seal shape, valve direction... etc...

Apply vacuum in the wrong direction and you could easily blow/invert a rubber seal...

The problem with the system not getting all of its fluid purged out of the shocks, is not pressure and vacuum, but rather the design and shape of the vessel, where you don't have a shock reservoir/top inlet/bottom outlet allowing for full fluid circulation, but instead, you have a single top inlet pot, and fluid does not dynamically move inside it, rather, the fluid moves in and out through the same pipe, based of pressure being positive or negative... This leaves some fluid that never gets touched at the bottom of the shock

If you insist on getting every single drop of fluid, you have 2 options, you either need to disconnect and remove every shock/strut, and turn it upside down, a few times, to drain the fluid at the bottom of the shock chamber...

Alternatively, you can look into flipping the car upside down somehow, so the shocks are higher then reservoir and return line... and fluid flows out... since mirrors, side panels, and tops are expensive, this is not an option, so back to disconnecting shocks...

Is it worth the effort?? maybe, maybe not, depends... clean fluid will extend the life of the system, no questions about it, but it will not reverse the hands of time on components, such as the pump, that wears out from constant grinding... components like the shocks, and their rubber that deteriorates over years... valves and their springs that sag over time... etc...

So is the benefits worth the effort and time???

Well, its not only about benefits and time, its about risk as well...

In some cases, working in a dirty wheel well, you could be running a very high probability of risk of introducing a spec of sand into the pipes... this is FAR more deadly to the components that junk dissolved in the fluid, giving it blackish color...

Best analogy of the ABC system I like to use is human body, yes we do open bodies up to do surgeries, but only when its needed by a medical conditions....

We never cut somebody's guts open as preventive maintenance... because the risk of infections far exceeds any possible benefits... not to mention that is inconvenience and costly to prep a surgery room for every 6 months physical at your PCP...
 

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bayhas,.
You are the man! (or person, to be politically correct). Thank you for the expertise, your knowledge base is quite appreciated. I was thinking about Gary's residual dark fluid and kindle's mystery fluid. Is it necessary to do a rodeo procedure to further mix the fluid before flushing or does repeated cycling of the level suffice? If the residual fluid does not mix that thoroughly in the struts and accumulators, can we assume kindle's mystery fluid may not have fully entered those components? And, hopefully a couple of Pentosin flushes asap will save some major repairs/headaches?
 

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I am returning my fluid which is not the green Febi S6161 but another Febi fluid and I am buying the Pentosin 11S thanks to bayhas for pointing to this matter.

I must admit I had my doubts when I saw the clear fluid which I ordered.

Should be all ready and good to go for my winter project when I get back from the Bahamas.
 

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First, in the replacement process for the 'bombs', I made sure all three working areas were essentially operating room clean. I sprayed them liberally 3-4 times with brake cleaner, then alternated with 'purple' detergent solvent then water/Simple Green then water for 3 more times, finally repeated with 3-4 more brake cleaner drenchings. There was nothing but clean metal/rubber hoses in the area I was working.
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Regarding the 'vacuum' question, I respect bayhas comments about that, but it would have been neat if it had worked!

Perhaps, instead of a 'rodeo', we can get rid of a LOT of the older fluid in the struts by just successive 'bleedings'. I've now bled a couple of times from each corner. The most fluid comes out when I have the car raised (with two dots), then do a bleed (both first and second bleeds produced dark fluid). With the car on a lift, the corner I'm bleeding result in the axle raising up into the wheel well (the rear wheels quite a bit, the fronts not very much). Also, if the car is then lowered onto the wheels, the car is VERY low. This to me means the dark fluid is coming out of the strut.

So, when the engine is run and the car is 'raised' again, new fluid is pumped into the strut. Since the fluid going into the strut is under a good bit of pressure, there must be some turbulence, leading to mixing of old/new fluid.

Thus, raising/bleeding(resulting in axle raising)/raising/bleeding 6-8 times (while refilling the reservoir between each cycle), could possibly lead to each strut containing 80-90+ percent new fluid. Since we are not yet into 'driving season' for the SL here in southeast PA, I'm going to give this a try! I'll probably cycle 2-3 times between each bleed to help provide more turbulence in the strut fluid.

Comments/suggestions appreciated.
 

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Well, after suggesting a way to get much if not all of the old fluid out of the struts in the previous post, my 'old scientific training' of 50 years ago made me want to experiment to see if the postulate could be tested (maybe proven by others later!).

I bled each corner 4 more times. The procedure is a little complicated, as the car MUST be supported by the wheels in order to get full 'up' on the struts via 2 red dots on the console.

I did the fronts by raising the car via the ABC, then raising it on the lift until the bottom of the wheel was about eye level. I then bled each wheel (you can push/pull on a tire to turn the steering wheel to far left/far right for better access to the bleed valves) with the car in the air. WARNING - if you do this, be sure the front wheels are straight ahead before lowering the car, or you could damage the front fenders, as the front end will be VERY low. When it was back 'on the floor', I checked fluid level in the reservoir, adding as needed, then started the engine and raised/lowered the car 3 times. Then, up in the air to repeat the process until it had been done 4 times (I'd already bled the front/rear twice when I did the 'bombs'). The 3rd time, the fluid coming out of the bleed screw and down the tygon tubing was pretty green/translucent, and the 4th time, it was quite translucent. I had revved the engine to about 2500 rpm in case higher rpm put the fluid into the struts faster (to get better turbulance)

On the rear, I had to take off the wheels each time for up/down with the lift to get easy access to the bleed screws (not nearly as flexible as I was 60 years ago!). Again, the 3rd bleed fluid looked pretty fair in the tygon tubing and the 4th one was quite good.

I used about 1 1/2 liters of Pentosin CHF 11S to do the four bleeds on all axles.

The attachment below shows a white paper towel onto which I had placed about 3 drops of fluid from: The fresh can (can), the ABC Reservoir (Res), and from the 4th bleed of all four axles (LF, RF, LR, and RR). As you can see from the picture, there is VERY LITTLE difference between the fluid from the can and that from any of the 4 axles bleeds.

Thus, I think I'll change my plan regarding the rodeo. I'll do it, then change the filter, then a few weeks later, I'll take a few drops from each bleed screw and check it against fresh fluid. If there is no more difference than I have now, I'll be confident that this 'multiple bleed' procedure was a success, and I'll wait until 2016 to do a system purge (did one in 2014). I'm even considering NOT doing a rodeo, but perhaps bleeding once more sometime this summer to see what color the fluid is. IF the bleed fluid is not dark, then I think I've accomplished what a rodeo would do without putting the higher pressures on the system that it seems to do.

Hope this might be helpful to anyone concerned about leaving the old fluid in the system at the struts.

PS: Bayhas, I agree that using a 'drive on' lift where the wheels are supported by the lift would make the rear sequential bleeds much easier. But, I'm not sure the fronts would work as well, as turning the wheels full L & R for bleed screw access might not be as easily done. However, when I built the hobby garage and installed the lift 9 years ago, I felt I'd want free access under the car, and the ability to change tires/wheels easily and do suspension work a lot more often than I'd want to do something with the wheels supported. So, I put in the asymmetric 2 post lift. My usage experience has proven that was the right decision.
 

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Discussion Starter #31
Well, after suggesting a way to get much if not all of the old fluid out of the struts in the previous post, my 'old scientific training' of 50 years ago made me want to experiment to see if the postulate could be tested (maybe proven by others later!).

I bled each corner 4 more times. The procedure is a little complicated, as the car MUST be supported by the wheels in order to get full 'up' on the struts by getting 2 red dots on the console.

I did the fronts by raising the car via the ABC, then raising it on the lift until the bottom of the wheel was about eye level. I then bled each wheel (you can push/pull on a tire to turn the steering wheel to far left/far right) with the car in the air. WARNING - if you do this, be sure the front wheels are straight ahead before lowering the car, or you could damage the front fenders, as the front end will be VERY low. When it was back 'on the floor', I checked fluid level in the reservoir, adding as needed, then started the engine and raised/lowered the car 3 times. Then, up in the air to repeat the process until it had been done 4 times (I'd already bled the front/rear twice when I did the 'bombs'). The 3rd time, the fluid coming out of the bleed screw and down the tygon tubing was pretty green/translucent, and the 4th time, it was quite translucent. I had revved the engine to about 2500 rpm in case higher rpm put the fluid into the struts faster (to get better turbulance)

On the rear, I had to take off the wheels each time for up/down with the lift to get easy access to the bleed screws (not nearly as flexible as I was 60 years ago!). Again, the 3rd bleed fluid looked pretty fair in the tygon tubing and the 4th one was quite good.

I used about 1 1/2 liters of Pentosin CHF 11S to do the four bleeds on all axles.

The attachment below shows a white paper towel onto which I had placed about 3 drops of fluid from: The fresh can (can), the ABC Reservoir (Res), and from the 4th bleed of all four axles (LF, RF, LR, and RR). As you can see from the picture, there is VERY LITTLE difference between the fluid from the can and that from any of the 4 axles bleeds.

Thus, I think I'll change my plan regarding the rodeo. I'll do it, then change the filter, then a few weeks later, I'll take a few drops from each bleed screw and check it against fresh fluid. If there is no more difference than I have now, I'll be confident that this 'multiple bleed' procedure was a success, and I'll wait until 2016 to do a system purge (did one in 2014).

Hope this might be helpful to anyone concerned about leaving the old fluid in the system at the struts.
You know what would make this 10 times easier, and possibly feasible to standarize?

An alignment rack lift, that kind that allows you to stand underneath the car, and work freely, but while the car is still supported by its own weight and wheels...
 

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Pentosin/Febi fluid only has a 5 year shelf life when it is sealed sitting on the shelf according to the manufacture, so you need to replace it AT LEAST that often when its in the car.

I would guess between a regular flush and this bleeding procedure you would get most of the bad old stuff out, but a rodeo is going to fully extend everything in the system to all the way up and down and doing a rodeo while flushing would likely be easier than repeatedly doing each bleed valve and would also yield better results.
 

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Discussion Starter #33 (Edited)
Pentosin/Febi fluid only has a 5 year shelf life when it is sealed sitting on the shelf according to the manufacture, so you need to replace it AT LEAST that often when its in the car.
I was going to disagree, but I am actually looking at a bottle of each Pentosin and Febi 6161 right this moment... CHF11s sure enough has an expiration date of 12/2019 (about 5years)...

06161 has none however...

 

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strange as I've only used the 11s and have no experience with the 06161. I can't imagine its formulation would be different enough that it wouldn't have the same life expectancy, otherwise it probably wouldn't be appropriate to be used interchangeably.

I know some of the very early models actually came from MB with the old red fluid, which is also used for the top and is the oderless kind.
 

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carguyshu,

I've seen quite a few comments about having a rodeo done on a car, and almost immediately one of the control valves starts misbehaving (gone bad). Thus, in my opinion, 'bleeding the system' as I've done would remove 80-90% of the 'old' fluid that is in the struts and closely associated with the valve bodies. Thus, there is much less likelihood that when a rodeo IS done that the valve bodies would pick up and be damaged by any foreign material.

I'll probably do a rodeo and flush again in a month or so. And, I do feel a lot better about that with essentially new fluid in the struts and valve bodies when I do the procedure.
 

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On mine I did the standard procedure of the raise/lower button and flush to get the majority of the fluid new. I then did 2 rodeos (what merc recommends) to try and dislodge crud that's in the valve block (my left front strut slowly raises when the car is in park, meaning fluid is leaking by one of the valves - this was happening before I did the fluid flush). I need to replace my accumulators (got red ABC light driving fast over a bumpy road) and will at least rebuild the front block at that time. Once I get this project done I'll do another flush while a rodeo is happening and hopefully be good to go for quite some time.

If I was someone else and just bought a car with dirty fluid I would do the raise/lower button and flush strategy and then a couple month later do a flush while rodeoing. That way when you rodeo most of the fluid in the system will be new lessening the chances of a valve block getting old crud in it. I would then every 2-4 years or 20-30k do the rodeo/flush moving forward.
 
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