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Discussion Starter · #1 ·
Long story short, yet not very short...I drove my truck to Colorado in December for the holidays. The first stop was in Salina, Utah and when I started my truck up in the next morning and released my hand brake valve it continuously leaked a great deal of air that has the oily smell of the compressed air system. The temperature was in the low 20s F (-6 C). The brakes released and the truck was able to build and hold air pressure. So I decided that the family could live with the smell of some air from the compressor. After about 20 or 30 minutes of running the truck and driving it around the valve stopped leaking The rest of the trip I did not set my brakes as the temperatures were -20 by the time I made it to northern Colorado. In the warmer temperatures the valve functioned well and I chalked it up to old rubber and another item on the list of items to replace given that the valve is approaching 40 years old.

I ordered a valve (A000 431 1916) from Teksan and it was here three days later!! I installed the valve and then started up the truck to test it and only then noticed that it is setup 180 degrees different than my valve. The original valve on my truck is the two port type and my airlines attached to the valve from the rear of the truck (this the configuration of several other trucks that I had my brother look at in his shop). Inside the cab the handle is released forward and spring tension hold the handle open. The Teksan valve was build to have the lines come in from the front of the truck if I would like to release forward as I am accustomed to doing. I have attached a photo of the two valves in the brakes released position.

I can turn the Teksan valve 180 and can probably get my lines to relax enough to attach from the front (I do need to replace all my air lines in the near future). However, I really wonder if the Teksan valve was put together improperly, which might also explain why there is a 1.65 mm gap in the plates that seem to be attached to the spring that tensions the handle motion. I have been in contact with Teksan this week and they will refund my money, but have not made to much progress confirming that all their valves operated in this manner. The original drawing of the Wabco valve (attached) in my truck shows that it should be built like my valve was and not the opposite configuration.

I have a few questions:

Has anyone rebuilt this valve? If so how much tension is on the side plates? There are two sockets in each of these plates that are probably used for tensioning the spring before assembly. I value my thumbs and have not yet disassembled my old valve.

If you did rebuild the valve where can one buy a rebuild kit?

Does anyone's hand brake valve have the airlines attach to the valve on the trucks forward side?



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I agree that you'd want to stick with convention and have the brakes release with the lever moving forward.

- I wonder if the valve is designed such that the lever / valve system can be swapped around to fit the housing either way , and Teksan flipped this one ?

- I pulled some photos and they mainly show the air lines connecting to the rear of the valve body ( Red Arrows ).

-One (Yellow Arrow) shows the lines to the front. Not all of these valves are the same exact pattern, but they are all UNIMOG parking brakes.

- Some photos show the lines approaching from the opposite side of the ports, making a turn and connecting up.

-The Double banjo fittings shown on a number of the valves would seem to be very easy to attach to either side of the valve body, without the right angle turn.

- The Original Valve seems to be reasonably priced in Germany. Personally, I'd have MEREX send me a new one and return the Teksan piece, if the price made sense. The price might not be the same as the Ebay bit that I pulled from the files, but the Dollar - Euro ratio is very good for now, 1 Euro = $1.09 at the moment. Nothing against Teksan, I don't have any experience with them as yet. You might get a New valve from Germany in a Mercedes box that is made in Turkey, Israel, Anywhere...


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26 Posts
Discussion Starter · #4 ·
Thanks Truktor!

I will tear apart my valve when I have a moment to see if I can flip the internals around. It looks like there may only be O-rings as seals so I will probably rebuild my valve.

At the top right of the schematic there is a note that details that the valve as originally designed may leak below -20 C but is operational to -40 C.


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