67 Brake fluid distribution block

[Al R.]

Is there a prefered way to clean a fluid distribution block that has been sitting on a shelf for 20+years? Also, how does the low fluid switch work? Does it float up and down with the fluid level or ground out electrically whenever fluid is present? TIA everyone!! Al

[Donald O.]

Re: 67 Brake fluid distribution block

The brake metering block is there to let you know that the system has lost either the front or rear brakes. If a brake hose were to rupture, the metering block would close off to that circuit. I believe that there is a ball inside that closes off that port, and completes the electrical circuit and displays the "BRAKE" light on the dash.

[Larry M.]

Re: 67 Brake fluid distribution block

Al:

I am not certain what the internals of this particular switch looks like. I have seen similar switches (other auto makers), and they have an internal piston block or blocks, o-rings, and possibly a return/centering spring.

When I decided to rebuild the one from my 1967 car, I sent it to DR VETTE Brakes (now CSSB Brakes in Florida). They took care of the details and sent me back my reconditioned switch. Not certain that CSSB does this work anymore, but you can call and ask. If they don't, they will know who does and if a rebuild kit it available for do-it-yourself-ers. CSSB is a major player in Corvette brakes and can be trusted to deliver a quality product.

These switch blocks are also available in reproduction from a number of Corvette Suppliers.

Larry

[Richard M.]

Re: 67 Brake fluid distribution block

Here's a original 67 Pressure Differential Switch I rebuilt last year. It was inoperational, because the internal valve was stuck. I removed the electrical switch, cleaned the internals and ran some fluid through it to free it up. Using small Philips screwdrivers, I had to carefully push each end of the internal shaft back and forth, very slowly, to free it. I replaced the o-ring for the switch, reassembled everything and it was all fine.

There are internal o-rings on the shaft so you don't want to go too far and tear them. The shaft has larger protrusions just to either side of the switch. If there is a pressure imbalance in one brake fluid circuit, the shaft will move to that side due to pressure from the other fluid circuit still pressurized. The shaft protrusion will hit the bottom of the switch(where the screw is), make electrical contact and then ground the "BRAKE" light on the cluster.

I'm unsure if there is a check-ball in each side to stop flow. Maybe there are piston valves on each end of the shaft to stop flow.

Rich

[Al R.]

Re: 67 Brake fluid distribution block

Thanks all, I removed the switch & looked inside as best as one can. It is mucky looking and there was some old fluid on the tip of the switch that looked almost like mud. Wonder if it will hurt anything to spray the block with brake cleaner to try to clean the insides and then try sliding the piston thing back & forth to remove as much muck as possible OR would it be better to use clean brake fluid to do the same thing?

[John H.]

Re: 67 Brake fluid distribution block

I'm unsure if there is a check-ball in each side to stop flow. Maybe there are piston valves on each end of the shaft to stop flow.

Rich

Rich -

There is no valving or flow function of any kind in the switch - just the spring-centered spool; if you lose pressure in one half of the system, the pressure differential just shifts the spool in the direction of the pressure loss, grounding the circuit to light the warning light.

[Richard M.]

Re: 67 Brake fluid distribution block

John....thanks for clarifying that.

Al, I think anything you use to clean and free it up would be ok, but just blow it out with compressed air to get it all out. Then some brake fluid to flush it out.

Rich

[Duke W.]

Re: 67 Brake fluid distribution block

You could soak the whole thing in a bowl of denatured alcohol. Then thouroughly blow dry and check that the piston is free before you reinstall.

Duke

[Al R.]

Re: 67 Brake fluid distribution block

I'll give the denatured alcohol a try since it won't evaporate as quickly as brake cleaner.

[Fred Y.]

Re: 67 Brake fluid distribution block

I just finished reading this thread. I am completing my cars reassembly process & at the brake MC area now. Yesterday before I installed my lines I removed the switch. There was a small amount of light brown fluid on it but no mud or gunk by any means. I saw the rubber O ring on the shaft along with 2 white plastic rings. I noted that this shaft would move in & out. I cleaned it up & reinstalled it back into the block, just normal snug tight. I am noting now that the same vertical shaft ( where my brown wire plugs on) no longer moves in or out; just stationary.

I was now going to run to my parts store for some new fresh brake fluid (DOT 3-4 as Lonestar recommends)

Before I start pouring in fluid I want to note that I am getting the blinking brake warning light on my dash, but I'm assuming that is due to NO BRAKE FLUID PRESSURE---So, does everything I have mentioned sound OK before I start with the fluid ? My assumption is the light will turn off once the system has pressure. But you know what happens when "you assume"---lol.

Thanks everyone. I'll sit tight till I hear back from you all.

Fred

[Joe L.]

Re: 67 Brake fluid distribution block

I just finished reading this thread. I am completing my cars reassembly process & at the brake MC area now. Yesterday before I installed my lines I removed the switch. There was a small amount of light brown fluid on it but no mud or gunk by any means. I saw the rubber O ring on the shaft along with 2 white plastic rings. I noted that this shaft would move in & out. I cleaned it up & reinstalled it back into the block, just normal snug tight. I am noting now that the same vertical shaft ( where my brown wire plugs on) no longer moves in or out; just stationary.

I was now going to run to my parts store for some new fresh brake fluid (DOT 3-4 as Lonestar recommends)

Before I start pouring in fluid I want to note that I am getting the blinking brake warning light on my dash, but I'm assuming that is due to NO BRAKE FLUID PRESSURE---So, does everything I have mentioned sound OK before I start with the fluid ? My assumption is the light will turn off once the system has pressure. But you know what happens when "you assume"---lol.

Thanks everyone. I'll sit tight till I hear back from you all.

Fred

Fred------


The brake warning light is activated whenever the fluid pressure in one of the two circuits is substantially different from the other. This causes the activating piston to deflect to one side or the other and activate the light. If there is no pressure on either side of the piston, the piston should remain centered and the light should not be activated. Of course, in your case, the piston might not be centered due to the work you've done on it. I think it should center when you add fluid and effectively pressurize the entire system. Otherwise, I think you might want to check your factory service manual. As I vaguely recall, there might be a procedure for centering the switch.

The other thing that activates the warning light is, of course, the parking brake via the switch under the lever console.

I was not aware that 1967 had a blinking brake warning light, though. 1969 does not.

[Fred Y.]

Re: 67 Brake fluid distribution block

Hi Joe, those were my thoughts since I removed the piston just to inspect it & make sure it was clean inside. Just the slightest amount of light brown fluid but that was it. The shaft simply moved up as I tightened the entire sensor back into the block. The black rubber O ring was still in good shape. I have double checked the E-handle & switch & it is working as it should. Yes , like the headlight bulb the brake light bulb blinks as well. I just returned from the store & will see what happens once the system is under pressure. I'll report back ----Thank you.

[Donald O.]

Re: 67 Brake fluid distribution block

Yes , like the headlight bulb the brake light bulb blinks as well. I just returned from the store & will see what happens once the system is under pressure. I'll report back ----Thank you.

Fred,
On a 67 only the red HEADLIGHTS indicator should blink, the red BRAKES indicator should not blink. It should be a steady ON light.
Don

[Fred Y.]

Re: 67 Brake fluid distribution block

UGGG I was using some spare bulbs I had left over from my 66 when I did the dash ? Well back under the dash I go. Don, do you recall which # bulb that is ?----I can look it up too----just tired now.I've been bleeding the brakes plus a dozen other things today.

[Donald O.]

Re: 67 Brake fluid distribution block

UGGG I was using some spare bulbs I had left over from my 66 when I did the dash ? Well back under the dash I go. Don, do you recall which # bulb that is ?----I can look it up too----just tired now.I've been bleeding the brakes plus a dozen other things today.

Fred,
just checked my data, it should be a # 1816. Same as the clock and turn signal indicators.

Don