Brake bleed procedure 2
Thread Starter
|
Senior User
Joined: Dec 2013
Posts: 348
Likes: 4
From: Bakersfield,CA
Brake bleed procedure 2
Have a non running 73 F250.
Noticed there was no fluid in the brake master cylinder, either front or rear chambers.
So set out to find the leak(s).
Every thing was dry with no trace of brake fluid?
While tracing all the brake lines, noticed a brass block on the drivers side on the front brake calipers discharge line from the proportioning valve, mounted on the cross member. The portioning valve is mounted on the frame rail.
The brass junction block has a pin on the under side.
Found in the archieves a discussion about this pin about 11 eleven years ago, titled "brake bleeeding procedure" in the 73-79 vintage section.
Apparently the 1979 model has the block with the so called bleed pin integrated into the proportioning valve.
There was considerable discussion and this pin thing was not resolved.
Apparrently for the F150 the pin is pulled out when bleediing the front calipers, while the pin is pushed inward for the F250.
Does any member know the purpose of this pin, how it works and what to do with it, when bleeding the front calipers?
Understand the right rear is bleed first, then the left rear, then the right front, then the left front.
Noticed there was no fluid in the brake master cylinder, either front or rear chambers.
So set out to find the leak(s).
Every thing was dry with no trace of brake fluid?
While tracing all the brake lines, noticed a brass block on the drivers side on the front brake calipers discharge line from the proportioning valve, mounted on the cross member. The portioning valve is mounted on the frame rail.
The brass junction block has a pin on the under side.
Found in the archieves a discussion about this pin about 11 eleven years ago, titled "brake bleeeding procedure" in the 73-79 vintage section.
Apparently the 1979 model has the block with the so called bleed pin integrated into the proportioning valve.
There was considerable discussion and this pin thing was not resolved.
Apparrently for the F150 the pin is pulled out when bleediing the front calipers, while the pin is pushed inward for the F250.
Does any member know the purpose of this pin, how it works and what to do with it, when bleeding the front calipers?
Understand the right rear is bleed first, then the left rear, then the right front, then the left front.
Lead Driver
Joined: Nov 2006
Posts: 5,217
Likes: 506
From: Pa.
Have a non running 73 F250.
Noticed there was no fluid in the brake master cylinder, either front or rear chambers.
So set out to find the leak(s).
Every thing was dry with no trace of brake fluid?
While tracing all the brake lines, noticed a brass block on the drivers side on the front brake calipers discharge line from the proportioning valve, mounted on the cross member. The portioning valve is mounted on the frame rail.
The brass junction block has a pin on the under side.
Found in the archieves a discussion about this pin about 11 eleven years ago, titled "brake bleeeding procedure" in the 73-79 vintage section.
Apparently the 1979 model has the block with the so called bleed pin integrated into the proportioning valve.
There was considerable discussion and this pin thing was not resolved.
Apparrently for the F150 the pin is pulled out when bleediing the front calipers, while the pin is pushed inward for the F250.
Does any member know the purpose of this pin, how it works and what to do with it, when bleeding the front calipers?
Understand the right rear is bleed first, then the left rear, then the right front, then the left front.
Noticed there was no fluid in the brake master cylinder, either front or rear chambers.
So set out to find the leak(s).
Every thing was dry with no trace of brake fluid?
While tracing all the brake lines, noticed a brass block on the drivers side on the front brake calipers discharge line from the proportioning valve, mounted on the cross member. The portioning valve is mounted on the frame rail.
The brass junction block has a pin on the under side.
Found in the archieves a discussion about this pin about 11 eleven years ago, titled "brake bleeeding procedure" in the 73-79 vintage section.
Apparently the 1979 model has the block with the so called bleed pin integrated into the proportioning valve.
There was considerable discussion and this pin thing was not resolved.
Apparrently for the F150 the pin is pulled out when bleediing the front calipers, while the pin is pushed inward for the F250.
Does any member know the purpose of this pin, how it works and what to do with it, when bleeding the front calipers?
Understand the right rear is bleed first, then the left rear, then the right front, then the left front.
The pin is used to bypass the metering valve when you bleed the front brakes. Pulling the pin out fully depresses the metering valve, so that fluid can flow right to the calipers instead of being delayed. This prevents air from being trapped in the proportioning valve when bleeding the fronts. You pull it out and hold it there prior to bleeding the fronts, then release it when you're done.
Thread Starter
|
Senior User
Joined: Dec 2013
Posts: 348
Likes: 4
From: Bakersfield,CA
In the stock 1973 F250 the front caliper metering block valve is separate from the proportioning valve. There is a steel brake line routed from the portioning valve to the metering block valve.
So is the pin pushed in or is it pulled out for the F250 with 8100 GVW?
Is the procedure used when using a vacuum pump to bleed the front caliper and/or the shade tree method of depressing brake pedal, lossening bleed fitting, then tighten bleed fitting, then releasing brake pedal.
What is the purpose of the metering valve?
Would guess the purpose might be to delay applying the full pressure to the front calipers and allow full pressure to the rear brakes to develop, first, before the full pressure is applied to the front brakes?
So is the pin pushed in or is it pulled out for the F250 with 8100 GVW?
Is the procedure used when using a vacuum pump to bleed the front caliper and/or the shade tree method of depressing brake pedal, lossening bleed fitting, then tighten bleed fitting, then releasing brake pedal.
What is the purpose of the metering valve?
Would guess the purpose might be to delay applying the full pressure to the front calipers and allow full pressure to the rear brakes to develop, first, before the full pressure is applied to the front brakes?
Lead Driver
Joined: Nov 2006
Posts: 5,217
Likes: 506
From: Pa.
The proportioning valve helps prevent rear wheel lock up as the vehicles weight is shifted toward the front wheels during panic braking situations .. The need for this was eliminated when rear anti-lock brakes were introduced .. On your specific truck (1973 8100 GVW) I don't have that info ..
Thread Starter
|
Senior User
Joined: Dec 2013
Posts: 348
Likes: 4
From: Bakersfield,CA
On the 1973 F250 the front brake caliper metering block release pin is pulled down when bleeding front calipers.
Pulling the pin downward allows brake fluid to flow to the caliper bleed fitting.
Believe failure to release metering block will result in only partially bleeding the front calipers.
Pulling the pin downward allows brake fluid to flow to the caliper bleed fitting.
Believe failure to release metering block will result in only partially bleeding the front calipers.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
With the system closed up, watch for subtle movement of the pin while a friend presses the brake pedal. If the pin moves OUT as it does on light-duty trucks, then you should pull it OUT while bleeding the fronts as well. In other words, let the truck tell you which direction to pull.
You are 100% correct. Brake fluid has to "push" against a spring-loaded plate to escape the metering valve and run out to the calipers. This mechanism must be bypassed while bleeding the fronts. Otherwise, air in the valve compresses FIRST and then the aerated fluid escapes the metering valve. Collapsing the metering valve spring lets fluid run right past without trapping and compressing any air stuck in the valve. The pin must be released after the bleeders are closed off.
You are 100% correct. Brake fluid has to "push" against a spring-loaded plate to escape the metering valve and run out to the calipers. This mechanism must be bypassed while bleeding the fronts. Otherwise, air in the valve compresses FIRST and then the aerated fluid escapes the metering valve. Collapsing the metering valve spring lets fluid run right past without trapping and compressing any air stuck in the valve. The pin must be released after the bleeders are closed off.
More Turbo
Joined: Nov 2003
Posts: 747
Likes: 26
A friend of mine had a pressure bleeder,didn't do the pin thing.Just opened the bleeder screw in order one at a time till it ran clear.The stuff that came out was nasty.
Trending Topics
Thread Starter
|
Senior User
Joined: Dec 2013
Posts: 348
Likes: 4
From: Bakersfield,CA
Noticed that gunk collects around the metering valve and proportioning valve.
It would be easy to over look the release pin on the front caliper metering valve when bleeding the front calipers.
It takes about 1 lb for force to pull the pin downward.
Using a small vise grip and a weight tied to the adjustment screw to hold the pin in release position, while bleeding the front calipers.
It would be easy to over look the release pin on the front caliper metering valve when bleeding the front calipers.
It takes about 1 lb for force to pull the pin downward.
Using a small vise grip and a weight tied to the adjustment screw to hold the pin in release position, while bleeding the front calipers.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
Thread
Thread Starter
Forum
Replies
Last Post
ktnissen
1967 - 1972 F-100 & Larger F-Series Trucks
11
Jul 12, 2017 06:35 PM
dthut
1973 - 1979 F-100 & Larger F-Series Trucks
8
Apr 10, 2017 07:49 AM
pbuffing
1973 - 1979 F-100 & Larger F-Series Trucks
10
Jul 31, 2011 04:33 PM
NC2X4
1973 - 1979 F-100 & Larger F-Series Trucks
27
Sep 15, 2010 10:54 PM
cassenbl
1999 - 2003 7.3L Power Stroke Diesel
9
Apr 27, 2008 12:14 AM