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1st Generation 1964 1/2 - 1973 - Questions & general discussions that apply to a specific year => 1967 Mustang => Topic started by: Hipo giddyup on May 09, 2017, 03:23:39 PM

Title: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 09, 2017, 03:23:39 PM
 The brake warning light on my 67' coupe had been on for sometime and I have had it disconnected at the brake warning light switch on the distribution block. The brakes work fine of course, but after looking into this issue, it sounds that the pressure differential valve within the distribution block is offset (as if you lost pressure to one corner of the braking system) and needs to be recentered to reset this warning lamp. This typically happens when you perform brake bleeding or repair work like this on the brake system. Does anyone have a description or can explain how to reset/recenter this pressure valve??

Attached is what I found on the internet but might not directly apply to the 67' Mustang application.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: BKnapp on May 09, 2017, 03:54:10 PM
That appears to be exactly how I have done it. Typically when I have bled my brakes, I start at the rear and end at front drivers side. So, now you have to very slightly open the fitting going to the back brakes and apply slight pedal pressure. Effectively you are creating a very small leak, which will cause the valve to move back to neutral. However, if you open it too much or press too hard, the valve will move past neutral and indicate a problem with the rear system. In this case you would need to repeat the process, using the front system.

I have always wondered if it is necessary to open the "outlet fitting at the distribution block". In a 390, that is not an easy fitting to get to. Assuming you were bleeding the brakes and finished in the front, could you go back to one of the rear bleeder valves and crack that open for the same effect?

Sometimes the valve will be stuck and have heard other people suggesting a hard sharp stomp on the pedal can dislodge it. I will be interested in others input.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67gtasanjose on May 09, 2017, 04:02:42 PM
Short BEST answer is rebuilt the block. Kits are available.

The seals break-down and so do the internal springs. This valve was INTENDED to center itself when new or like new.

Now, others might mention how to center the valve, there is a bolt/fitting made to screw into the switch location temporarily while bleeding, it prevents movement while bleeding the system. That would be the "alternative way" IMHO
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Bob Gaines on May 09, 2017, 04:12:53 PM
Short BEST answer is rebuilt the block. Kits are available.

The seals break-down and so do the internal springs. This valve was INTENDED to center itself when new or like new.

Now, others might mention how to center the valve, there is a bolt/fitting made to screw into the switch location temporarily while bleeding, it prevents movement while bleeding the system. That would be the "alternative way" IMHO
+1. NPD sells the centering pin fitting i believe.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: ruppstang on May 09, 2017, 08:50:22 PM
+2 NPD has them, I made my own.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Brian Conway on May 09, 2017, 10:25:12 PM
BKnapp has got it.  I never open anything on the valve body but you do need to plug the sensor back in.  Essentially a balancing act using the front right brake cylinder bleeder and the right rear brake cylinder bleeder.  One person slowly and firmly pressing on the brake pedal and the other letting air/fluid slowly out of the front or rear cylinder.  The person on the brake pedal lets the other one know when the light goes out and that's the time to close the bleeder.  You'll get the hang of it.  Of course the valve body just may need a rebuild.  Brian 
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Bob Gaines on May 09, 2017, 10:50:58 PM
BKnapp has got it.  I never open anything on the valve body but you do need to plug the sensor back in.  Essentially a balancing act using the front right brake cylinder bleeder and the right rear brake cylinder bleeder.  One person slowly and firmly pressing on the brake pedal and the other letting air/fluid slowly out of the front or rear cylinder.  The person on the brake pedal lets the other one know when the light goes out and that's the time to close the bleeder.  You'll get the hang of it.  Of course the valve body just may need a rebuild.  Brian
Keep in mind that no brake fluid comes out of the sensor switch opening . The sensor switch is isolated from the fluid on ether side of the depression (for sensor pin) in the piston by rubber o rings .
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 09, 2017, 10:57:14 PM
 Thanks for all the responses. I do know that it is dry under the warning switch so the seals apparently are still good in the block. I will try bleeding the rear brake first with gentle  pedal pressure to see if it centers the pin again. If that doesn't work I will try the front brake, then ultimately I might have to rebuild the block. I will hopefully attempt this this weekend and post  my results. 
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Bob Gaines on May 10, 2017, 01:01:16 AM
I hope you are luckier then I. When ever I have had the problem on a original system it is the result of the piston sticking to far forward or too far backward and is stuck because of corrosion inside. Rebuilding is the only remedy. The only reason for me posting is so that you don't spend too much time going back and forth trying to balance it. When the cars were new or on a completely restored system the bleeding scenario was a typical and more likely solution. After 50 years the more likely solution on a otherwise original unrestored distribution block is to rebuild the block. Hopefully you will break it free and not have to rebuild.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: ruppstang on May 10, 2017, 08:51:23 AM
I hope you are luckier then I. When ever I have had the problem on a original system it is the result of the piston sticking to far forward or too far backward and is stuck because of corrosion inside. Rebuilding is the only remedy. The only reason for me posting is so that you don't spend too much time going back and forth trying to balance it. When the cars were new or on a completely restored system the bleeding scenario was a typical and more likely solution. After 50 years the more likely solution on a otherwise original unrestored distribution block is to rebuild the block. Hopefully you will break it free and not have to rebuild.

+1 The only time I have been able to reset it was after I rebuilt the block and pushed it off bleeding the system.
Good luck
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 10, 2017, 09:26:38 AM
Thanks guys. So then my next question is what would you mean as "rebuilding"? What components of the block are available, the distribution valve seals?? are they still available?? Or are you simply referring to taking the block apart for a good cleaning / removing any corrosion? The car has never sat for many months/years without being moved/used even when I was restoring it. But still, it is 50 years old. What are the chances the warning switch is bad or could there be an elecrtical issue, even though the offset of the valve is easy enough to do.?
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67gtasanjose on May 10, 2017, 09:55:27 AM
Pretty sure most places carry the kit, like NPD, Virginia Mustangs, West Coast Classic Cougar etc.

Some carry the kit for the distribution valve WITH proportioning valve,  I think they are about $30

NPD carries just the distribution block kit for example: https://www.npdlink.com/store/products/mustang_rebuild_kit_brake_pressure_differential_valve-169774-350.html

PDF file on building BOTH: (I would do both while the system is open) https://d2zl5tj7gmc4tr.cloudfront.net/store/content/download/instructions/2b257-4ak.pdf
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 10, 2017, 11:34:55 AM
Thanks for that info and the links. My car is 4 wheel drum so I only have the distribution valve to rebuild. Looks like that is the only and best answer at this time, just rebuild it! I'm ordering the kit today as well as the locking pin to keep the valve in place when you re-bleed the brakes. I'll try and take some pics of what I am dealing with to maybe help others. (But sometimes I get into a groove and next thing you know, I have already completed the job before I remember to get my phone out!  :-[ )
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 10, 2017, 11:52:52 AM
I also found that the kit number you linked is not correct for my application. Since mine is drum brakes, I will need kit # 2B257-3A.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: mtinkham on May 10, 2017, 02:13:58 PM
I could not get the spool valve unstuck on the car I was restoring. I soaked it in an array of liquids for three weeks. I tried hot water, brief heating with a propane heater, Ice, 120 lbs of Compressed Air (Caution!!!!I restrained with a vice and clamps to prevent getting punctured by the projectile), tapping, hammering, and even swearing. Nothing moved the valve.

There was no way to attach anything to the valve and the opening was too small for needle-nose pliers. I contemplated drilling out the back end, but decided not too.

The application was a July 67 Coupe, 4 wheel drum, manual brakes.

Reinstalled the valve with my hopes and expectations smashed...left wire disconnected.

A quick continuity test can be performed between the brass case and the terminal.  If the spool valve has shifted off center it completes the circuit to ground causing the light to come on.

This was the only thing that I gave up on during this 7 year restoration. The circuit does not provide any advance safety measure, as it is the loss of brake pressure that causes the light to come on....you will feel the loss of pressure simultaneously.

Completely and Utterly Defeated,
Mark
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67gta289 on May 10, 2017, 03:26:58 PM
In a previous post Marty recommended heat, then whacking it on a block of wood. This did not work the first try, so I gave it much more heat the second time, grabbed it with a Kevlar glove and gave it a hard whack.  Popped right out.    The compressed air and soaking did nothing for me either.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 10, 2017, 04:53:55 PM
Yikes! I don't want to destroy my distribution block so wish me luck. I have another as a spare and might practice on that first. I'm one of those people who can't stand something being on the car that isn't working.  ;D
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67gtasanjose on May 10, 2017, 05:11:43 PM
Get yourself a couple of fittings that fit the back side of the block, cap one off. (use your imagination or buy a cap fitting). Install the capped fitting into one of the holes (on the back side of the piston), 'thread' (using a tap) the inside of the other fitting (where normally the tubing is at...again, thread this 2nd fitting into the block on the back side of the stuck piston. Thread a grease zerk into this 'threaded fitting', pump up the pressure with a grease gun, if this won't move it, perhaps a little heat but WATCH OUT! When that HOT GREASE expands...IT WILL BURST OUT ABRUPTLY! (have a field of rags handy in the vicinity to catch the piston softly) Works every time I've tried it but use eye protection, long sleeves, gloves...you know...be smart.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Bob Gaines on May 10, 2017, 07:00:04 PM
Or  -  NPD page 93 distribution block 28075-2A .  70.64 .   ;)  In case you don't need the satisfaction of DIY or feel like it would be cheating . ;D
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67350#1242 on May 10, 2017, 09:00:41 PM
+1 on the grease gun.  You can put in a tremendous amount of pressure with just a few squeezes of your hand.
I've used the gun on dist. blocks and brake caliper pistons very successfully and with no damage to the parts - usually will not need heat with this.
Kurt.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: C6ZZGT on May 11, 2017, 03:02:04 AM
OK I have this issue as well on the wifes 67,I found the rebuild kit and new block in the NPD catalog BUT I don`t see the " the centering pin fitting i believe."--- Anyone have a part number ?
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: ruppstang on May 11, 2017, 08:50:10 AM
It is in the tool section. 914-7 $10.00
They are easy to make for about $1.25
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67gtasanjose on May 11, 2017, 09:21:57 AM
It is in the tool section. 914-7 $10.00
They are easy to make for about $1.25

Agree, +1

Keep in mind, the piston needs centered BEFORE using this tool. The tool or pin on the end does not need to be hardened so you can get a bolt with correct thread pitch, allen bolts work best because you can grasp them in your cordless drill easier to machine it down (using a cut-off wheel)
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: sah62 on May 11, 2017, 01:46:01 PM
I could not get the spool valve unstuck on the car I was restoring. I soaked it in an array of liquids for three weeks. I tried hot water, brief heating with a propane heater, Ice, 120 lbs of Compressed Air (Caution!!!!I restrained with a vice and clamps to prevent getting punctured by the projectile), tapping, hammering, and even swearing. Nothing moved the valve.

There was no way to attach anything to the valve and the opening was too small for needle-nose pliers. I contemplated drilling out the back end, but decided not too.

The application was a July 67 Coupe, 4 wheel drum, manual brakes.

Reinstalled the valve with my hopes and expectations smashed...left wire disconnected.

A quick continuity test can be performed between the brass case and the terminal.  If the spool valve has shifted off center it completes the circuit to ground causing the light to come on.

This was the only thing that I gave up on during this 7 year restoration. The circuit does not provide any advance safety measure, as it is the loss of brake pressure that causes the light to come on....you will feel the loss of pressure simultaneously.

Completely and Utterly Defeated,
Mark

I provide the kits that most of the catalog vendors carry, and I have some tricks described on my web site for getting the piston out. Please send me a PM and I'll follow up with you this weekend after I return from a short day job business trip.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: C6ZZGT on May 12, 2017, 11:12:02 PM
thx for that-I guess i would have got that far back in the book eventually !
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 15, 2017, 11:14:07 AM
 This question is more for SAH 62. I got the distribution block out of the car but of course the pin is stuck. I have block off's for all the ports except for of course where the pin will exit and one of the rear ports that needs to use the grease gun to expel the pin. Can you tell me the thread size that I will need for the block as well as what would work with the grease gun? I have a close match but it comes apart once I apply pressure from the grease gun  between the grease gun in the fitting.  The match is dead on for the thread size of the distribution block. Thanks for any help
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: sah62 on May 15, 2017, 12:37:57 PM
This question is more for SAH 62. I got the distribution block out of the car but of course the pin is stuck. I have block off's for all the ports except for of course where the pin will exit and one of the rear ports that needs to use the grease gun to expel the pin. Can you tell me the thread size that I will need for the block as well as what would work with the grease gun? I have a close match but it comes apart once I apply pressure from the grease gun  between the grease gun in the fitting.  The match is dead on for the thread size of the distribution block. Thanks for any help

Sorry, but I don't recall the port size off the top of my head. I do, however, have some tips to describe what you need:

https://www.musclecarresearch.com/grease-gun-pressure

You might need to visit your local NAPA to find the right combination of fittings.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67gtasanjose on May 15, 2017, 01:03:10 PM
This question is more for SAH 62. I got the distribution block out of the car but of course the pin is stuck. I have block off's for all the ports except for of course where the pin will exit and one of the rear ports that needs to use the grease gun to expel the pin. Can you tell me the thread size that I will need for the block as well as what would work with the grease gun? I have a close match but it comes apart once I apply pressure from the grease gun  between the grease gun in the fitting.  The match is dead on for the thread size of the distribution block. Thanks for any help

I waited for sah62 to answer first since you asked. I knew he had a link to another website that spelled out various details.
I have now borrowed an image from that site that shows a setup similar to what I described earlier but I used what I already had in my "spare parts", including just a regular tubing fitting, I threaded the inside of the regular tubing fitting (using a tap/die set) to accept an old grease zerk. Hardware store got NONE of my money again this time ;)

Your block will differ from the picture but the arrangement is basically the same.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 15, 2017, 10:16:19 PM
 Thanks for all the advice guys. I took a 5/16 inverted flare plug, drilled it with a 15/64 bit, then used a 1/4 x 28 tap and placed a zerk fitting in it. I capped off all ports except the exit port where the pin would exit . Then after slowly applying grease gun pressure, I  felt a "give"and the pin popped towards the exit hole. I then took some needle nose pliers and pulled the pin out the rest the way. Hopefully this info can help the next person.

My pin didn't look as bad and corroded as others I've seen so I would suspect that bleeding the brakes could have shifted my pin back to position without removing it from the distribution block or taking a block off the car. Either way this was a guaranteed fix, to remove it and be able to put new seals on it. Next I'll reassemble, use the positioning tool to keep the pin centered, get it back on the car, bleed the brakes, and hopefully the brake warning light won't be staying on!!

Title: Re: 1967 brake pressure warning light / pressure valve
Post by: jwc66k on May 16, 2017, 12:26:43 AM
I like your style - make your own tools. Good job.
Jim
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 17, 2017, 08:35:07 PM
 Well, I reinstalled the rebuilt distribution block and bled all brakes but since I reattached the warning light wire, the brake warning light is still illuminated on the dash. I know I positioned the piston correctly before I inserted the positioning tool that I bought from NPD. Does anyone have any ideas as what could be the cause?  Could there be a grounding issue? Any help would be greatly appreciated .
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: midlife on May 17, 2017, 09:45:39 PM
The bulb and circuitry measures the difference in voltage between RUN-only power and the MC brake signal.  When the MC is grounded, the light will go bright.

What happens when you remove the connector from the MC?  Does the light go out?  No?  Then put the connector back on and remove the voltage regulator plug from the VR.  You may have a bad regulator, a pinched wire somewhere such that the purple/white wire for the MC brake signal is grounded.  You can check for a pinched wire by removing it from the MC and measuring resistance between it and chassis ground.  A pinched wire should be on he order of 1 ohm or less; a good wire should be on the order of kilo-ohms or higher.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 17, 2017, 10:05:13 PM
 Thanks Randy, I removed the wire from the master cylinder distribution block and the light went out. This is where we started from before I even rebuilt the distribution block. I just thought maybe there was a ground somewhere that I missing. I do remember reading where someone said I could slowly bleed one of the rear/front brakes and see if it repositions the pin. That'll be my next step.   :'(
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Brian Conway on May 17, 2017, 10:54:15 PM
Yeah I bought and used  that ' tool ' and found it useless.  The back and forth balancing and bleeding method works.  Takes two people - read my post again - it's not rocket science.  You'll get it.  Brian   
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67gtasanjose on May 18, 2017, 05:59:03 AM
The tool is intended to PREVENT the piston of the distribution block from moving during the bleeding procedure. It should only be or have been removed AFTER the brakes are found to be functioning 100% normal. IMHO, there could be no way the piston could have moved to one side or another if this tool was used the way it was intended. Using your image, the 'V" recess in the center of the piston is where the tip is the electric plug sets, preventing the switch from closing to ground. If the piston remained centered during the bleeding process, you should be able to remove the switch and see the "V" notch centered in the hole. (Fluid will not leak out of a properly rebuilt distribution valve). If the piston IS CENTERED, the switch may be at fault. If the valve is NOT centered, the bleeding procedure mentioned earlier will help you (but it still is a PITA to get this centered again this way, especially if working alone or with unskilled help)
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 18, 2017, 07:49:30 AM
Thanks for the info. I ABSOLUTELY made sure it was centered, and measured where the V notch would be once I installed the pin back into the block. I then inserted the tool and made it tight enough , it should have been in the notch. There is also NO WAY to look into the block and see the notch , the hole is as small as any brake line hole. I will try to gently let pressure off the brakes , one end at a time, to see if that will work.

I thought about getting another warning light switch but an NOS unit looks to be pricey and not an easy find. I am also unsure if that is absolutely the problem but will consider it if bleeding the brakes does not solve the issue.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: sah62 on May 18, 2017, 09:46:52 AM
I have the piston re-centering procedure described here: https://www.musclecarresearch.com/faq-page#n329
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67350#1242 on May 19, 2017, 01:37:28 AM
I didn't see anywhere in the thread where you checked out the switch.   the brass pin in the end should have spring action when pushed in.  I've seen them stuck closed.   When pushed in there should be continuity between the pin or plunger and the connecting contact.
Of course the contact will be broken when the pin springs back out.
Kurt.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 19, 2017, 01:22:09 PM
 I did not realize that there is a spring within the brake warning light switch. I will remove it and see if the pin can move. How much of a travel are we talking 16th of an inch?
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67350#1242 on May 19, 2017, 04:07:21 PM
I would guess 1/16 to 1/8".   Put an ohmmeter across it and see if it's stuck closed.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 19, 2017, 04:54:03 PM
Sorry, not good with electrical. What should it read?? I do have a multi meter..
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67350#1242 on May 19, 2017, 08:03:04 PM
Zero ohms with plunger pushed in.  Infinity with plunger out.
Use lowest ohm scale on meter.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 20, 2017, 12:54:03 PM
 So I had my meter set on the lower scale. It looks like it was registering  1.  with the plunger not depressed. When I depressed the plunger in it went to 0.00. Does that sound correct? Seems like it is working?
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: jwc66k on May 20, 2017, 01:39:40 PM
So I had my meter set on the lower scale. It looks like it was registering  1.  with the plunger not depressed. When I depressed the plunger in it went to 0.00. Does that sound correct? Seems like it is working?
Yes. Put the tips of the two leads together and you should get 0.0. This is the meter check technique used to verify zero when checking resistance.
Jim
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Brian Conway on May 20, 2017, 03:40:03 PM
Test the sender just like you would test the door switch/plunger for your int. courtesy lights  Brian
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67350#1242 on May 20, 2017, 06:38:44 PM
Yes when it shows 1 that means open or no continuity.  Closed (plunger in) should be zero.  Seems to be working.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 20, 2017, 08:34:11 PM
 Thanks again, now it's onto the brake bleeding to get it back in position.   Fingers crossed   ::)
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: Hipo giddyup on May 29, 2017, 11:27:35 PM
Finally got time to finish bleeding the brakes, to reposition the pin in the distribution block. I loosened the right rear bleeder while my wife gave easy brake pedal pressure and the safety light went out! I found that a slow stream of brake fluid seeping from the wheel cylinder was just enough pressure to reposition the pin. Hopefully this thread will help others as it did for me. Thanks to all who helped out along the way!!
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 67gtasanjose on July 19, 2020, 09:43:52 AM
+2 NPD has them, I made my own.

For the home hobbyists who don't wish to wait on or buy the brake warning light bleeding tool, an 1/8" x 1/8" rivet and a standard 3/8" inverted flare nut make for a cheap and easy to come up with ideal substitute.
Title: Re: 1967 brake pressure warning light / pressure valve
Post by: 1967FEGT on July 19, 2020, 11:42:41 AM
Also you won't get a valve centered by bleeding it. I used an NOS unit I could move the shuttle valve easily with a pick before installation. I hadn't put the lock tool in it and my assistant stuck her foot on the pedal. The bias was to the front so I put a towel under the master and removed the brake line from the front of the master to the distribution block. Looked via the hole in the flair. You'll see the silver shuttle valve.  Push it back centered with the pick, lock it. Reinstall the brake line and start from the left rear, right rear, right front and left front.  Put the switch back in and you should be good to go! Best of luck to you!