I recently purchased from a popular on-line Z-car supplier a rebuild kit for the rear brake proportioning valve on a '71 240.  The problem is that rebuilding of the valve assembly appears all but impossible.  Somehow a spring has to be compressed about half way into a cylinder and held in place while a spring clip is pinched, inserted and pressed against the top of the spring.  I have read some comments on this forum that no, it is not possible to rebuild, but then why would a reputable supplier sell the kit?  Is there a special tool to enable the job?

Your thoughts would be appreciated.

Thanks

The "proportioning valve" on the early 240Z, mounted at the rear, is actually more like a hydraulicly operated timer than anything else.  The cylinder compresses the spring and fills with fluid. This essentually delays the rear brakes and allows the front brakes to engage first. When you let off the brake (pedal) the fluid looses pressure and the cylinder returns.

That is when the system is clean and in good condition. Now 45 yeaes later a lot of these valve cylindees are seized in the loaded position and no longer reset. I have never seen one of these proportioning valves apart. Most people change to a willowwood  adjustable and replace it or move it to the engine bay just after the brake switch.

Can you post a photo of the kit?

 

Also, post the supplier and part number. Maybe someone here is familiar with it. There are some smart people on here who may be able to give you an educated answer.

EuroDat,

Thanks for replying.  Here is a photo of all the bits and pieces, lined up in the order of disassembly.  Arrows point to the three parts of the rebuild kit.  They are two seals, and an o-ring that fits on the threaded end plug.  To hold the spring in compression while inserting the washer and spring clip is the challenge.  

Given that the original rubber seals were in not-bad condition when they came out, I'm wondering if seal replacement is even needed.  There was dirt and grime inside, so should I find another old valve, leave it assembled, and clean it out with air and brake cleaner, alcohol, naptha or whatever?  

Ok, Thanks for posting the photo. Thats the kit from motorsport I believe. http://www.thezstore.com/page/TZS/PROD/classic21j/24-5556

It's the first time I have seen someone use that kit. Following with much interest;).

I can understand your dilema with the circlip.

I haven't tried to do this myself (yet), but your picture gave me an idea...

Try using two loops of fine-diameter fishing leader line (plastic) to tie and knot the spring into compression.  Position your loops at the 12 and 6 o'clock position of the spring circumference.  Drop the seal, the valve and the spring into place.  The two loose ends from each loop of line will stick out of the bore.  Insert the circlip, with the loose ends of lines going through the centre. Once the circlip is clicked in place, use an X-acto blade to cut the loops of line and then use tweezers to pull the remains out of the bore.

It might work.

12 minutes ago, Namerow said:

I haven't tried to do this myself (yet), but your picture gave me an idea...

Try using two loops of fine-diameter fishing leader line (plastic) to tie and knot the spring into compression.  Position your loops at the 12 and 6 o'clock position of the spring circumference.  Drop the seal, the valve and the spring into place.  The two loose ends from each loop of line will stick out of the bore.  Insert the circlip, with the loose ends of lines going through the centre. Once the circlip is clicked in place, use an X-acto blade to cut the loops of line and then use tweezers to pull the remains out of the bore.

It might work.

I what thinking something along those lines, too.

Good idea Namerow. It might be a tight fit between the valve stem and the spring to get a blade in and cut the line.

I was thinking something like that with the circlip, but the circlip here is some bodgy style clip without the eyes. If you were to swap it for one with two eyes you could then use fishing line to compress the circlip, push the spring and circlip into position and release the fishing line. Of course I have never done it, so the technique sounds solid, but reality could prove to be way different.

SteveJ,

The kit was purchased from Motorsport Auto, part number 24-5556

 

Thanks,

Thanks. I could have sworn I saw a post in the past from Philip @240260280 on rebuilding the valve.

I can remember a thread in the past about someone changing one after a brake upgrade. Philip posted a nice photo of the valve then, but I can't find the thread on my tablet. Ill have to do a search next time I am on the laptop. I would like to see what Philip turns up with.

There was a discussion, I think on this site four or five years ago, about changing the spring and then we decided it was not worth it because the valve was not really a proportioning valve, but a delay valve so to speak. Not many people try to repair them. Most just swap them for a manually operated aftermarket proportioning vavle.

I pulled my "later" version apart and cleaned it along with the brake indicator switch. It is a completly different design and function.

 

Edited April 30, 20177 yr by EuroDat

I was wondering if you could compress the spring and insert a screw driver from the side port to hold the spring down while the circlip is placed in the bore?