Kelsey-Hayes 86652 Combination Valve Autopsy

This Kelsey-Hayes combination brake valve includes pressure differential and metering functions. It does not include any parts to provide proportioning functionality. I was told that it was originally used on a 1973 Dodge motor home. One side is marked KH 86652.

The other side is marked with a date code of "3 039" (the 39th day of 1973 was February 8).

I decided to disassemble it to see if it's rebuildable. Follow along as I tear it down!  Tools needed:

  • 5/8" box or open end wrench
  • 7/8" box or open end wrench
  • 5/16" open end wrench
  • Dental pick (or other small, pointed tool)
  • Nail set (or other tool to push with)
  • 6-32 threading tap
  • 6-32 x 1" machine screw
  • 6-32 nut
  • Flat washer with 1" OD and 1/8" ID

Step 1: Remove the pressure differential switch using the 5/8" wrench. Note the o-ring.

The internal parts can be removed by first removing the brass tube seat that is pressed into the fluid port on the end of the body. The seat can be removed by tapping it with the 6-32 threading tap, threading a 6-32 x 1" puller screw into the hole, and removing the seat with a few twists of a wrench. Start by tapping the opening in the seat.

You can create a puller tool using a 6-32 x 1" machine screw, a 6-32 nut, and a flat washer with 1" OD and 1/8" ID. Thread the nut onto the screw. Insert the screw and nut into the hole in the washer. Thread the screw into the hole you just tapped in the seat.

Turn the nut clockwise with the 5/16" wrench.  The seat will be removed cleanly. Muscle Car Research sells a puller tool if you'd rather not source the parts yourself. The seat can be reused if it isn't damaged during removal, so please be careful if you intend to rebuild the valve. I do not have replacements and I don't know abyone who does. If you look inside the valve through the port where you removed the seat you'll see a slotted brass piston. We need to push that out from the other side, so turn your attention to the metering end of the valve body.

Remove the rubber cap (if yours is still present; sorry I don't have replacements for these caps, either). Remove the fitting using your 7/8" wrench. Note the o-ring. You'll see a brass cap under the plug.

Remove the metering valve assembly by pulling on the steel pin. Beneath the metering valve assembly you'll see a rubber cushion, a brass cap, and a small spring. Remove each part and set it aside. None of these parts are included in my rebuild kit because they typically don't need to be replaced.

With the metering valve removed you can now push out the pressure differential piston. Push it out, and note the two o-rings and the brass spacer. Here the the internal parts so far.

Now we need to disassemble the metering valve. It's held together with a very small steel retaining ring just above a steel cap.

Remove the retaining ring. I like to do it by clamping the long end of the steel valve pin in a bench vise with cushioned jaws. You can then push down on the steel cap to compress the large spring, releiving pressure on the retaining ring. You can remove the ring with a dental pick. I include a replacement retaining ring in my rebuild kit because they often get lost when trying to remove them.

With the retaining ring removed you can separate the remaining parts of the metering valve.

The valve is now ready for cleaning and rebuilding. Please see our rebuild article for detailed instructions.