Kultulz,

These things are too old for (R)ABS that didn't come about until later years.

 

Yes? ...

D'oh!

How about the proportioning valve then? This is multi-choice right? ...

 

Heh, multiple choice.

Yeah, the brake lines connect to a device down there, the nitpicky purists will call it a Pressure Differential Valve and explain why it's not a Proportioning Valve blah blah blah but technical details on the name don't matter so much here and now.

 

DAMN!

...wrong again ... sigh...

 

Thanks everyone. I'll likely have more to ask but for now I am satisfied. Gonna work on the frame before any of the engine compartment gets an overhaul.

 

FoMoCo refers to this as the Brake Pressure Differential Valve beginning in 1967, when it was originally introduced.

But some people are unaware, call it a proportioning valve.

If people do not know what the correct FoMoCo terminology for parts is, it will cause confusion for the "chimer-inners" and they may get the wrong info or even worse, the wrong part(s). Not pleasant!

 

I got it right what do I win


All that part does is turn on the dash light when the system see a uneven psi between front & rear systems.
What I don't get is why you cant tell when the pedal goes to the floor before the light comes on that you have an issue and need that light to tell you?
Dave ----

 

A 3 day road trip anywhere in the US in a rented 2017 F150 Stupor Crew with Chris (ctubutis) aka Mr. Dazed & Confused aka Aunt Blabby, aka Mr. Fixit, aka Mr. Clean doing all of the driving!

Why only 3 days? Because after 3 days, you'll be ready for the "funny farm!"

 

I agree! In certain situations, I guess.

In this case, the OP is just trying to identify objects from a 1,000 foot view so he knows what they are in general, and we're not even sure what C was pointing at. So, I figured exactly correct terminology in this case isn't necessary.

Ha!!!!!!

I quite honestly want to do more driving than I did this past trip so long as I have time to learn the new vehicle + how the engine behaves at lower altutude.

And the brakes, I need time to get used to the new brakes.

I am *way* behind the times in terms of newer vehicles, all the computer-controlled stuff they have these days isn't necessarily intuitive and I have (had) zero experience with anything like that - hooking up my Android phone to the car entertainment system (which has its own built-in apps), having said entertainment system feed audio from the desired device & app can be irritating.

My own newest car is my mom's 11 yo Nissan Altima, pretty bare-bones but intuitive - I turn ***** to tune the radio and adjust the volume, the way it's been since I was born.

 

It isn't enough just to see me humiliated in this thread? ...

The chances of having a complete failure is minimal with a split hydraulic system. The light is simply telling you that there is either a pressure loss and/or failure somewhere in the system.

So, whenever braking, always keep your eye on that lamp...

 

It does a bit more than just that.

The Proportioning valve / Pressure Differential valve / Metering valve/ Combination valve, all these terms are basically correct for the brake systems pressure differential/ proportioning/metering valve.


The metering valve portion of the valve does not allow any pressure to the front disc brakes till a threshold pressure is reached. The threshold pressure is low compared to the maximum pressure in the braking system, this allows the drums time to take up the slack that typically is greater than in disk brakes.

The pressure differential valve portion measures the inlet pressure on from both sides of the Master Cylinder If one side ends up greater than the other either due to a leak down stream in one circuit or a fault in the master cylinder in one circuit it will trip a switch lighting the brake light on the dash.

The proportioning valve portion of the valve reduces pressure to the rear brakes, the rear brakes require less force/pressure than the front brakes. If equal braking force were applied at all four wheels during a stop, the rear wheels would lock up before the front wheels. The proportioning valve only lets a portion of the pressure through to the rear wheels so that the front wheels apply more braking force.

See below cut away of an old school cast iron Ford combination valve that explains it far better than I can.

 

If Mr. Dazed and Confused had turned the radio on in the F150, then turned the volume and search dials by hand, he woulda heard:

"I'm just an Okie from Muskogee." or "I went to a turkey roast down the street, people down there eatin' like wild geese. I'm on my way...to Alabam."

I'm not gonna comment on Mr. Dazed and Confused braking ability (or the complete lack thereof), except to say that without a seat belt, I woulda become a hood ornament!

 

Interesting thread, even as it veers off subject. More info in this long thread:

https://www.ford-trucks.com/forums/1...ve-delete.html


I have to wonder how the metering valve function ever got approved. As designed, it has one serious flaw. If pressure is lost in the rear brakes (major leak, etc.), the "threshold pressure" is never reached and the front brakes won't work, either.

I experienced this several years ago. I had a rear cylinder fail and lost all fluid to the rear circuit. As designed, the red warning light illuminated when I stepped on the brakes. However, the light was exceedingly superfluous, as the complete lack of braking was my initial observation.

So for a dual system required to be redundant, it was a total fail on Ford's part. A single failure took out both systems. Was there a fraction of the front braking power available? Maybe, but it wasn't much. I had to downshift to get stopped. Glad my Dad taught me I will lose all brakes one day, and to always be prepared for such an event.

 

HUH ? I think you have something confused here.

The metering valves threshold pressure is completely independent of the rear circuit and not linked to the rear circuit at all it is just a spring valve that opens once predetermined PSI is reached.
Remove the rear circuit in it's entirety and it's operation does not change one bit. As long as the master cylinder can generate pressure the operation will not change.

Now the only time this could get messed up is if you had a failure/leak in the seals separating the circuits in ether the master cylinder or combination valve. As this would allow pressure to bleed from one circuit into the other, under normal operation you would never even know this is happening as both sides are in equilibrium hydraulically. But when you lose one circuit the seals separating the circuits are now called in to action (normally they are just along for the ride) and if they are degraded and not fully sealing pressure will bleed from circuit to the other reducing brake effectiveness in the operational circuit.

Likely what happened is you lost the rear circuit and the front circuit was bleeding some pressure in to the rear circuit either at the master cylinder or the combination valve leaving you with almost no brakes.

 

I am not jumping on you but just using your FORD tech descriptions (and they are correct when refering to FORD vehicles of the period) which actually vary from manufacturer to manufacturer.

This is a quote from the referring URL posted somewhere below-

What is being described here is known in the industry as a COMBINATION VALVE. It serves three purposes, actually four-

1) Front Brake Metering Valve

2) Pressure Differential Valve

3) Rear Brake Proportioning Valve

4) Rear Brake Residual Valve

A stand alone PRESSURE DIFFERENTIAL VALVE only serves one purpose. If any other valve system is included in the assembly, it's proper name (not necessarily FORD's) is COMBINATION VALVE.

FORD's early designs usually had a stand alone PRV, a stand alone MV (front disc) and a stand alone Proportioning Valve. As engineering progressed (FORD around 1970), the valving was combined.

There was a very extensive discussion here sometime back discussing this and FORD's Basic PN's on the valve(s).