1967 - 1969 GM 3905525 Metering Valve Autopsy

This Bendix metering valve was removed from a 1969 Chevrolet Chevelle. According to my parts catalogs the original applications include all 1967 - 1969 Chevrolet vehicles and 1967 - 1969 GM A-bodies equipped with front disk and rear drum brakes. The original GM part number for this valve is 3905525.

You can click on the pictures below to see larger versions of the images.

I'm going to disassemble this valve to see if it's rebuildable. Follow along as I tear it down!  Tools needed:

  • 1 5/16" socket or large open end wrench
  • Nail set
  • Dental pick
  • Small hammer

Start by removing the rubber dust cap from the end of the valve body. The cap is marked "Bendix 2225847 MADE IN U.S.A." around the top edge with "ABI" and "116" in the middle. Be careful when removing the cap because it's not included in my rebuild kit (though an excellent reproduction is available). Note the end of the rod that's protruding from the valve.

Now flip the valve over and remove the plug from the end of the valve body. Note the o-ring on the plug. Look inside the valve and you'll see a black rubber sealing washer. The o-ring and the seal will be needed in a rebuild kit. Remove the o-ring with your dental pick.

Flip the valve over again and push on the end of the protruding rod using the nail set and small hammer. As the rod is pushed into the valve the rest of the spool valve that it's part of will be forced out of the valve. Continue pushing gently until the spool valve can be removed.

The rod that you noticed earlier is part of a spool valve that controls the flow of brake fluid through the valve body. The spool valve blocks fluid flow until fluid pressure increases enough to compress the spring a certain distance inside the valve body, eventually exposing the outlet port. When the outlet port is exposed brake fluid can flow through the valve.

Note the u-cup seal at the bottom of the valve body. This seals the rod and allows it to move in response to changes in fluid pressure. The u-cup will need to be included in a rebuild kit.

Disassemble the spool valve by removing the individual parts in order.

Muscle Car Research offers a rebuild seal kit for this valve. Complete rebuild instructions are available in another technical article.