Flushing out the hydraulic system

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Chris Wright
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Flushing out the hydraulic system

Postby Chris Wright » Sat Feb 18, 2006 7:28 pm

Has anyone flushed out their hydraulic system?

I plan on removing the fluid from the reservoir and changing the filter at the bottom of it. When I refill it with fresh fluid, I want to flush the old fluid out of the system. Has anyone done this?
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uncleestevan

Postby uncleestevan » Tue May 02, 2006 5:20 pm

me too

I want to do the same job and would like help
 

demet
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Postby demet » Tue May 02, 2006 6:59 pm

All I do is disconnect the low pressure return line from the steering box and let the fluid drain. If you want to flush the system with fresh fluid just plug up the hose that you disconnected and pour fluid into the reservoir. The fluid will move down through the pump and out the steering box end.
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Chris Wright
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Postby Chris Wright » Wed May 03, 2006 12:12 am

When I first asked this question I was contemplating something along the lines of what "demet" suggested. It now seems that I, and quite possibly "uncleestvan", have had a problem with a sticky regulator and to that end I wanted to flush the system under pressure in an attempt to clean the regulator, I did the following and it seems to have worked, the brake warning light no longer comes on.

First you must identify the correct filter as there are two types of reservoir. Go here:

http://www.realoem.com/bmw/select.do?vi ... E24&arch=1
(Look under "32 Steering- 32 20 Lubrication system")

to tell which one you have from looking at the type of cover and knob on the reservoir. Click on the one that represents yours and it will give you a diagram showing how it all goes together and a parts list.

The seemingly most common number is 32 41 1 128 167
($15 at https://www.autohausaz.com)
The other number is 32 41 1 128 919 ($23 also at Autohausaz)

Discharge the accumulator by pumping the brakes 20/30 times. Remove the top "C"clip and screen. Get a turkey baster to empty the reservoir. Remove the remaining"C"clips, spring, cap and filter and clean the reservoir (the two I've done have had a gray film coating everything, let us know if yours does too).

Install the new filter, filter cap, spring and "C"clip. Fill the reservoir and run the engine. Go through the steps of discharging the accumulator, empting the reservoir, refilling and running the engine 2 or 3 more times to flush out the old fluid in the lines, steering box, pump and regulator. To bleed the system, turn the steering wheel lock to lock 4 or 5 times with the engine running. Reinstall the top screen and it's 2 "C"clips. Don't forget to discharge the accumulator before you top up the reservoir to 3/8"(10mm) from the top. If you don't the system will be over filled. I used about 3.5 quarts of ATF to do all of this.
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jhankins71

Postby jhankins71 » Thu Aug 09, 2007 2:12 am

I seem to have the same problem as Uncleestevan has described in this thread:
http://bigcoupe.com/phpBB2/viewtopic.php?t=2544
(brakes work fine under normal conditions but very hard pedal for the first .5-1 second in a panic stop). To address this I'm planning on replacing all of the low pressure lines (very old) in the hydraulic system and flushing the fluid. My questions are:
1. has flushing the fluid resolved this specific type of hard brake problem (I know there are several version of hard brake pedal issues)
2. has anyone tried using any fluid designed specifically for flushing PS systems or should I stay away from this stuff given the multi function design of our cars and the fact that it does not use PS fluid?
Thanks
-John
 

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Chris Wright
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Postby Chris Wright » Thu Aug 09, 2007 3:39 am

jhankins71 wrote:I seem to have the same problem as Uncleestevan has described in this thread:
http://bigcoupe.com/phpBB2/viewtopic.php?t=2544
(brakes work fine under normal conditions but very hard pedal for the first .5-1 second in a panic stop). To address this I'm planning on replacing all of the low pressure lines (very old) in the hydraulic system and flushing the fluid. My questions are:
1. has flushing the fluid resolved this specific type of hard brake problem (I know there are several version of hard brake pedal issues)


I trust that you have pumped the brakes and watched the fluid level rise and fall to confirm that the accumulator is OK?

2. has anyone tried using any fluid designed specifically for flushing PS systems or should I stay away from this stuff given the multi function design of our cars and the fact that it does not use PS fluid?
Thanks
-John


I think I'd stick with a flush designed for ATF fluid, no real reasons why, just a feeling. I've used a flush made by Sea Foam called Trans Tune on an old truck auto tranny and on the can it also recommends using it in the power steering system, but haven't used it in the PS system yet. I was thinking of giving it a shot if the system started to act up again.
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MG 1100
 

jhankins71

Postby jhankins71 » Fri Aug 10, 2007 3:37 am

Chris,

Thanks for the pointer to Trans Tune. This looks like useful stuff should a few flushes with ATF not help. But you raise an excellent point about the accumulator, the level in the resevoir does not seem to change when I pump the brake so it sounds like that may be the cause of my hard pedal problem. I can't really check it right now. Front end is jacked up and I've got the altenator out out to replace the bushings, which makes it a good time to replace the low pressure PS hoses (I think mine are really shot). I'm going to do the hoses this weekend and do a couple of flushes of ATF and check the results. Changing the accumulator looks like a PITA. Any advice if/when it comes to that?

Also, the diagram in the Bentley manual shows the primary supply from the resevoir going to the PS pump from a fitting at the bottom of the resevoir. On my car the supply to the PS pump is connected to a fitting that comes off the side of the resevoir about an inch from the bottom (not shown in the diagram in the manual). The fitting on the bottom of the resevoir is connected to the return line from the steering box. It looks to me like some PO has switched these two lines. I would think that the supply line should always be at the lowest point in the resevoir. I also think this means that supply connection is sitting above the filter when it should be below it. Agree?

Thanks

-John
 

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Chris Wright
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Postby Chris Wright » Fri Aug 10, 2007 4:33 am

jhankins71 wrote:Also, the diagram in the Bentley manual shows the primary supply from the resevoir going to the PS pump from a fitting at the bottom of the resevoir. On my car the supply to the PS pump is connected to a fitting that comes off the side of the resevoir about an inch from the bottom (not shown in the diagram in the manual). The fitting on the bottom of the resevoir is connected to the return line from the steering box. It looks to me like some PO has switched these two lines. I would think that the supply line should always be at the lowest point in the resevoir. I also think this means that supply connection is sitting above the filter when it should be below it. Agree?

Thanks

-John


Nope, the diagram in Bentley's seems to be wrong, your lines are hooked up right. It's common not to suck the supply off of the bottom where any sediment can settle. In this case the return from the steering box flows up into the bottom and out through the filter and if the filter clogs, the pressure will raise the spring loaded cap and act as a pressure relief.
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'87 635Csi

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MG 1100
 

jhankins71

Postby jhankins71 » Tue Aug 14, 2007 12:22 am

The saga continues...

I replaced the main supply and return hoses in the hydraulic system and flushed it with Trans Tune for good measure. I've cured all of my problems with leaks but the hard brake problem is still present. One area which I'm confused about is exactly what I should see in a normally functioning accumulator. When I pump the brake pedal I can see the level in the reservoir rise and fall with each pump of the pedal by about 1/4". After about 20 strokes I think the level in the reservoir has also risen a slight amount, maybe a 1/4". Does this indicate a functioning accumulator or a dead one? I looked at the posts on this topic but I could not find any specific info on exactly what to look for to determine if the accumulator is functioning properly.

Thanks

-John
 

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Chris Wright
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Postby Chris Wright » Tue Aug 14, 2007 2:20 am

When you pump the brakes with the engine off, the level should rise from below the screen to within 3/8" of the top edge of the reservoir and then disappear to below the screen again when you start the engine up as the accumulator recharges. Each pump discharges a small amount from the accumulator until it is empty.

Sounds like your accumulator is bad.
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Brucey
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Postby Brucey » Tue Aug 14, 2007 6:12 pm

-I concur. The level change as the accumulator is discharged is several inches.

cheers
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jhankins71

Postby jhankins71 » Sun Sep 09, 2007 3:08 am

Update: I purchased and installed a new bomb and the hard pedal problem has been cured. It took a bit of time to get all the plumbing for the regulator disconnected but I managed to get the bomb and regulator out, replaced some of the low pressure hoses and clamps, cleaned things up and got it all back together with no leaks. A couple of the high pressure fittings took a bit of work to get loose but all in all, not too bad for stuff that has been in place for 23 years. Thanks to all for the helpful advice.

-John
 


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