Metering and Proportioning Valves

[tqwrench]

Been researching the threads here and on google and other places looking for answers today. Here's my question: Is there a source for a rebuild kit for the metering valve on my truck, 69 F250 disc/drum/power brakes (factory)? The valve is C8TZ-2B161-A.

Reason I ask, I recently had a situation where a proportioning valve in another car I own failed and it got me to thinking if that one was bound up (the isolation function/idiot light portion of it did not work), the one in my truck is likely stuck too. What happened on that car was I had a front pipe rupture (while stopped at a light thankfully - was able to control the car), and it's supposed to set the brake warning lamp and isolate the fronts from the rears. It didn't, no matter how many times I'd pump the pedal it would just bail fluid out of the broken pipe. Had to use the parking brake to baby it out of traffic.

Before I dive headlong into this and touch or disturb something made of "unobtanium," I thought I'd ask the sages for advice here.

My thought process is this, if I can't rebuild it, I need to work around it. The way I see that happening is to get a later model combination valve (Kelsey-Hayes style), plumb that in and use a plain tee (Dorman 785436 3/16" pipe tee) to replace the metering valve.

Sound correct?

[ultraranger]

If your pressure differential valve looks like this:





You can get new rebuild seals through Muscle Car Research.com.

https://www.musclecarresearch.com/valve-kit-whead1

https://www.musclecarresearch.com/valve ... rhead-drum


https://www.musclecarresearch.com/brake-valve-tool

[FORDification]

Keep in mind that this is JUST a pressure differential switch. It doesn't meter fluid and has no properties of a proportioning valve. It's only function is to monitor the front and brake circuit pressures and to turn on a warning light if the pressure isn't equal....like what happens when a brake line fails.

If you'd rather just buy a new one, go to the Mustang supply houses. The similar-vintage Mustangs use the same pressure differential switch.

[Madman]

Absolutely correct. It shows being out of balance between press at some point between the front and back lines, which moves the little piston and sets off the light. Trick is to figure out which way it moved and bleed the opposite one a tiny bit until the light clears .

[tqwrench]

Thanks for the replies, good information.

My proportioning valve looks like this:

Prop valve.JPG

My question is this, and the following link may answer my question (cannibalize a combo valve), what can I do with the metering valve? I found mine frozen, since the FSM told me to depress the button during bleeding (it is indeed frozen).

https://www.musclecarresearch.com/1970- ... ve-autopsy

So I guess as it sets right now, one option is to use the kits mentioned in links here to rebuild the prop valve, and buy a reproduction combination valve to cannibalize the guts for the separate metering valve on my truck OR do like I originally posted and just convert to a combination valve like the one found here:

Combo valve.JPG

Does that sound right?

[ultraranger]

The valve body in the photo and in the diagram I posted isn't a 'proportional' valve. It's a pressure differential valve.

The two valve bodies you have pictured are disc/drum combination valves. They each contain a combination of a pressure differential valve as well as a proportioning valve, housed in a common valve body. One of the valves pictured is a 1970 type disc/drum combination brake valve. It doesn't have a metering valve contained in it to the front disc brake circuit. The other valve (with the plunger on the forward end) does have the metering valve function.

F100s prior to 1973 didn't come with factory front discs. Factory discs weren't optionally available on the trucks until 1968 and this was only on the F250 and F350s.

A factory disc/drum brake '68-'72 F250/350 would have used the very same pressure differential valve as the drum/drum brake equipped trucks. The only difference in '68-'72 was the addition of a stand-alone metering valve plumbed inline to the front disc brake circuit.

In 1973, (manual) front disc brakes were standard equipment on all F100-F350 trucks. Ford redesigned the brake valves and integrated (3) separate functions into the disc/drum brake valves: metering to the front disc brake circuit, pressure differential sensing between the primary and secondary brakes and proportioning to the rear drum brake circuit.