Brake proportioning valve-anyone take theirs apart?

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jjs2800cs

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Redoing our 2800CS suspension and brake system. After only 5 years found rear brake cylinders (new 5 years ago) fairly gummed up and one might have been frozen. Have cleaned them up but are concerned that the brake proportioning valve also probably needs cleaned and flushed. Anyone open theirs up? Any pictures?

I am not worried about doing so but worried that the couple of seals/orings might not be standard and thus I could end up with a paper weight. Some threads say to have them rebuilt, others to get a new one if can find one, still others say to eliminate and go with a tee.

The first two options are expensive, the tee might be an option but might have lock up problems as some have had. The valve looks like a simple device so should we open it up?

I did find a thread on a Porsche 914 forum of a similar valve used on a 914 that someone did open and cleaned theirs successfully.

Thanks

jjs2800CS
 
JJS

Yes, they can be opened. I have no photos of the innards. They are not very complex. Undo the 4 bolts that hold the cylindrical housing to the cast piece. Note, that there is a paper gasket here that you should try and save. This cylinder has a large spring inside that will be exerting force on the housing as you undo the bolts. Once this is off there should be a circ-clip holding the piston in place. Remove and pull apart. Clean and inspect everything. The inside of the housing will likely be pitted from rust. White Plains can bore and re-sleeve these units, replace o-rings and paint outside. The adjustment on these units is the on the end of the cylindrical housing. Just leave that alone (unless you have reason to adjust).

Alternatively, La Jolla or Coupe King may have equivalent replacements for these. Do a search on the forum for past topics.

One of the difficult tasks in removing these is getting the 3 pipe connections loose without stripping the hex nuts.
 
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Did you replace the flexible brake hoses first? Mine looked great, convinced myself that they couldn't be the problem so I replaced the subject valve. Same problem so I replaced the hoses, bingo! This was eight years ago. The valve was available through a generic auto supply warehouse that uses Centric to rebuild calipers, it was probably bought from Centric.
 
Thanks for the replies thus far.

Yes I am replacing the rear rubber brake lines as they have essentially expanded shut probably contributing to the rear cylinders being bad as it seems as though little fluid has been reaching them. I have already rebuilt the front calipers and replaced those 4 rubber hoses. Also master cylinder has been rebuilt.

I want to take apart and clean the proportioning valve as it is the last piece of the brake system that has not got attention. So I will give it a go and see what happens.

I'll post pictures if successful.

Any other comments?

Thanks

jjs2800cs
 
I just did this exact work 5 days ago. Pulled it apart as Sven described. I ended up just cleaning it up and putting back together with existing parts however I have very low confidence in the ability of internal seals to work properly as there was some pitting evident. I decided that since I am switching to DOT 5 I would not worry too much if it leaks since I could just deal with it later and wont wreck any paint work in the process.

Might try to White Plains (this may be White Post) for re-sleeve though I recall Luis did not have a good experience with them on his brake master cylinder. Have not tried to locate a new one the way Chris described.

It's not a big deal to open it up. Be careful as Sven mentioned as the spring does impart significant load as the 4 hex screws are removed. Might be easier to do in a press to maintain pressure or have an assistant put their weight on the unit for a controlled release with screw removal. I cut a new paper gasket for the rebuild. Mine did not have a circ-clip though was from a 72 Bavaria so there may be some subtle differences (or mine is more messed-up than I think it is).

Good luck, let me know if you locate an alternate source.

Drew
 
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afeustel

Thanks for the reply. I plan on taking apart this weekend. As an reasonably cheap alternative as one of the replies suggested look at this,

http://www.iemotorsport.com/bmw/E9-E3-brakes/wwvalve.html

It is a manual unit and would have to be adjusted to suit I suppose. Also it looks like it only has one outlet so would need a tee for both rear brakes. Anyone have any experience with this for normal steet driving?

Thanks

jjs2800cs
 
Valve disected, cleaned, reassembled.

Got the valve off of the 2800CS. Took apart to check condition. Found it was fairly clean inside. No pitting, bore clean, seals looked reusable. Only had to make a new gasket for the spring housing.

Photos show the sequence. As an earlier post cautioned, when loosing the 4 allen screws, it is a good idea to use a clamp to relax the heavy duty spring inside.

Pretty straight forward procedure, inspect, clean, assemble, and paint. Toughest part was getting the 3 brake lines loose!

We'll know if it still works in a few weeks when car is back together.

jjs2800cs
 

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Well done thanks for posting, I should have done this when I did my rear subframe project
 
The big spring was compressed the same way it was taken apart with the large clamp. Check the photo upon taking apart.

Thanks

jjs2800cs
 
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