Kelsey-Hayes 86652 Combination Valve Rebuild

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This document describes how to rebuild the Kelsey-Hayes 86652 combination brake valve using a new rebuild kit available from Muscle Car Research LLC. Tools needed:

  • 7/8" open end or box wrench
  • 5/8" open end or box wrench
  • 9/16" open end or box wrench
  • 9/16" brake line fitting or plug
  • Dental pick
  • Nail set or other small pushing tool
  • Clean brake fluid
  • Liquid ammonia
  • Set of bore brushes
  • Brake cleaner
  • Steel wool

The rebuild kit provided by Muscle Car Research LLC includes the following parts:

  • O-ring seals
  • Metering valve seal
  • Meterig valve retaining ring

Arrange your valve, tools, and rebuild kit on a clean work surface. Let's get started! The first step is to inspect the valve and make sure that the exterior is undamaged. Check the port threads for damage. If any of the port threads are stripped or damaged you're better off finding another valve. If your valve passes the exterior inspection you're ready to disassemble it and inspect the internal parts. Disassemble the valve as described in our Kelsey-Hayes 86652 Combination Valve Autopsy article. Soak the metal parts for a few hours in a container of liquid ammonia. Ammonia does a great job of softening tarnish on brass, but be careful of the smell! Remove the parts, flush with water, and polish with steel wool. Clean the bore of the valve with the bore brush and make sure that the bore is perfectly clean - any dirty residue that lingers in here can cause a leak! Finish cleaning the parts using brake cleaner and cotton swabs. A rusty valve can be cleaned up by chelation. Lay out the clean parts and your rebuild kit.

We'll start with the metering valve. Install the new seal onto the steel pin with the pin grooves at the thin end of the seal. It helps to lubricate the seal with clean brake fluid. Note the orientation of the seal on the pin!

Install the brass retaining ring on the end of the seal.

Install the steel "hat" over the thing end of the seal.

Install the large spring, the steel cap, and the small retaining ring. This is the trickiest part of the rebuild process because it's really easy to lose the retaining ring - be careful! I find it easiest to mount the partial assembly in a bench vise with cushioned jaws. Add the steel cap (note the orientation) and push down on it to compress the spring. You need to push the cap down far enough to clear the groove in the end of the pin. Holding the cap down with the spring compressed, push the retaining ring into the groove - can can let the spring decompress when the ring is in place. You might find it easier to install the retaining ring if you push it into place with a pair of needle nose pliers or a dental pick.

Install the brass end cap with the beveled side towards the seal.

Here's the fully assembled metering valve. It's ready for installation, but you need to install a few other small parts first.

Insert the small spring into the fluid port at the bottom of the metering valve port.

​Install the small brass cap with the "hat" side toward the small spring.

Install the rubber cushion on top of the small brass cap, centered around the cap.

You're now ready to install the metering valve. Lubricate the seal with clean brake fluid and push it into place with the long end of the steel ping facing outwards.

Install the large o-ring onto the metering valve plug. Lubricate the o-ring with clean brake fluid.

Screw the plug into place using your 7/8" wrench. Stop turning when you feel resistance.

Add the rubber cap and the metering valve is finished.

Now let's work on the pressure differential part of the valve. Gather the parts and the two small o-rings.


Lubricate the o-rings with brake fluid and install them on the piston. Note that the brass spacer must be installed before the larger of the two o-rings.


Push the piston into place using a nail set or other small pushing tool.


Push the piston just far enough to ensure that the groove between the o-rings is lined up under the hole for the switch terminal! If this alignment is off your brake valve warning light will come on.


Seal the end of the valve body by reinstalling the brass tube seat using a 9/16" brake line fitting or plug.


Here's what the tube seat looks like after installation.


Lubricate the last o-ring with brake fluid and install it on the switch terminal.


Screw the switch terminal into the valve body. The rebuild is finished!


Now you can reinstall the valve in the car and reconnect the brake lines to the valve. Start each line by hand as best you can to ensure that the fittings are threading in straight and smooth. Be careful - it's easy to cross-thread the fittings and damage the threads. Tighten each fitting with a flare nut wrench. You may need to tighten, loosen, and re-tighten each fitting multiple times to obtain a leak-free seal. Add brake fluid, bleed the brakes, and check for leaks.

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