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Question about rear air brakes on an 86 F700

Jakex120

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Aug 29, 2018
Messages
69
Location
Kentucky
On your third picture there's a round object that looks like a vegetable can hanging under the right side of the front axle. Do you know what that is? I don't recognize it.
Yeah..its something emissions i think that has dropped down from its mount dangling down with vac hoses..will try to get more pics up soon ..maybe this weekend
 

DMiller

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Feb 21, 2010
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Hermann, Missouri
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Cheap "old" Geezer
Ford's Tomato Soup cans!! Can remember culling those rusted leaking messes out of a old pickup or truck systems!! That and the Air Injection stuff as the air pumps locked up or tubes rotted away.
 

mitch504

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Feb 27, 2010
Messages
5,776
Location
Andrews SC
No master cylinder for air brakes. You will have a foot valve either under the floor or up under the dash. Looking at those air lines going into the firewall, I'm betting on under the dash. Just look at what your brake pedal moves.
 

Steve Frazier

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Oct 30, 2003
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6,599
Location
LaGrangeville, N.Y.
That style of brake is pretty easy to service and very reliable. The rear cans are the dangerous ones, the second can is spring loaded to set the rear brakes for parking. That spring is under a great load. If you ever find you need to change a diaphram you have to be very careful. Make sure you chock the wheels as you'll be releasing the parking brake in the process. On the trucks I've worked on there's a "key" on the side of the air chambers, a threaded rod with a T on the end. You insert it in the hole you see in the chamber and twist it until it locks in to the park brake mechanism. Tighten the nut on the threaded rod until you can't tighten anymore and then and only then can you release the band clamp on the chamber to expose the diaphram. It would be best to have someone who has done it safely before show you the procedure, do something out of sequence and you could get seriously hurt.
 

DMiller

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Infamous 370 2V Two Barrel even more gutless than my 366 LP GMC
They both do tend to be Energizer bunnies running on and on and on!!!
 

Jakex120

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Joined
Aug 29, 2018
Messages
69
Location
Kentucky
Infamous 370 2V Two Barrel even more gutless than my 366 LP GMC
They both do tend to be Energizer bunnies running on and on and on!!!
Gutless as in weak?..haha..hope it fires at least..i gotta go back and take a good look at the distributor..one of plug wires dont seem right..also looks like my frame is cracked in the pumpkin pic..darnit!
 

Jakex120

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Joined
Aug 29, 2018
Messages
69
Location
Kentucky
I think that crack is a ty-wrap.
Your right..i see it now..as it crosses the hole opening..that one was starting to turn my stomach..I have it parked just off the gravel drive a bit and lately haven't been able to really crawl around under there because of wet ground which makes slick clay mud..so just kinda pointed the phone under there and hoped for best picture.
 

DMiller

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Feb 21, 2010
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Hermann, Missouri
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Cheap "old" Geezer
Not so much Weak as in SLOOOWWWWW!! Enganears gave them gears and use them all, all the time for these Applications!!!
 

56wrench

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Joined
Dec 4, 2016
Messages
2,074
Location
alberta
if you can't get the caging bolt in properly, and the keyhole inside is cocked off to the side, it indicates the dangerous spring is broke and requires a different removal approach to remove the brake pot
 

Jakex120

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Joined
Aug 29, 2018
Messages
69
Location
Kentucky
if you can't get the caging bolt in properly, and the keyhole inside is cocked off to the side, it indicates the dangerous spring is broke and requires a different removal approach to remove the brake pot
Haven't thought about a chance of broke up springs in the cans..I will tend to them most certainly if at start up they dont release the spring brakes..if i do get the truck running soon I'm clueless as to what to expect the brakes to do..have watched a few YouTube videos concerning some pressure checks and test but will probably seek help from some friends with experience with them..just that the largest truck I've owned was a Ram 3/4 ton..nothing with air brakes however.
 

DMiller

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Feb 21, 2010
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Location
Hermann, Missouri
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Cheap "old" Geezer
On the ones that either externally or cross leaks bad enough a engine compressor would not keep up would vise grip the operating rod extended then connect shop air set to 110# off a regulator to the spring can side, impact the clamping bolt on service side then knock the clamp away and release the air.
On dump trucks where the cans got aggregate eroded would lay under the differential, would gas axe steel or sledge the aluminum cans until spring was free
Generally had a loader bucket in the way to catch the parts. NOT a fun day.
 
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