The Ford Barn

jkeesey · 12-11-2013, 01:51 PM

Does anybody on here know about BIG truck brakes? I am having an issue with an F5 where the wheel cylinders will not release once depressed.

super flat · 12-11-2013, 02:01 PM

Possibly the master cyl is not returning all the way or the return hole in there is plugged.

jkeesey · 12-11-2013, 02:07 PM

I was thinking the same thing. The piston is returning all the way because I can feel it on the end of the pushrod. Maybe the release valve inside is sticking?

oliverguy · 12-11-2013, 02:41 PM

I had a 45 ton and a half that had the same problem. Truck had vaccum assisted brakes. There was a leak in the tubing leading to this vaccum booster. Once I fixed the leak the brakes would release.

jkeesey · 12-11-2013, 03:16 PM

Quote:

Originally Posted by oliverguy

I had a 45 ton and a half that had the same problem. Truck had vaccum assisted brakes. There was a leak in the tubing leading to this vaccum booster. Once I fixed the leak the brakes would release.

That sounds like the military style air brakes, similar to a tractor trailer. This setup has a separate booster that runs on vacuum. Im starting to think it was never assembled properly by the previous mechanic but im not sure.

alan · 12-11-2013, 10:59 PM

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you did not state the year of your truck--I have a 51 F5 ex-army truck with a remote booster located under the floor bolted to the frame, if the piston in that booster does not return the brakes will be locked up. When I asked about re-building this booster I was quoted between $500/600 dollars, I plan on removing it from the truck. My 41 1 1/2 ton has the same brakes and since I am not hauling a heavy load they work just fine--in fact I converted to dual master cylinder using a F350 master cylinder from a 68-72 Ford truck

12-11-2013, 01:51 PM	#1
jkeesey Senior Member Join Date: Apr 2011 Location: Glenmoore Pa Posts: 1,644	Big Truck Brakes? Does anybody on here know about BIG truck brakes? I am having an issue with an F5 where the wheel cylinders will not release once depressed.

12-11-2013, 02:01 PM	#2
super flat Senior Member Join Date: Jan 2011 Location: west bend wi Posts: 314	Re: Big Truck Brakes? Possibly the master cyl is not returning all the way or the return hole in there is plugged.

12-11-2013, 02:07 PM	#3
jkeesey Senior Member Join Date: Apr 2011 Location: Glenmoore Pa Posts: 1,644	Re: Big Truck Brakes? I was thinking the same thing. The piston is returning all the way because I can feel it on the end of the pushrod. Maybe the release valve inside is sticking?

12-11-2013, 02:41 PM	#4
oliverguy Senior Member Join Date: May 2010 Location: Reading PA Posts: 241	Re: Big Truck Brakes? I had a 45 ton and a half that had the same problem. Truck had vaccum assisted brakes. There was a leak in the tubing leading to this vaccum booster. Once I fixed the leak the brakes would release.

12-11-2013, 10:59 PM	#6
alan Senior Member Join Date: Jul 2010 Location: UPSTATESC Posts: 669	Re: Big Truck Brakes? Sponsored Links (Register now to hide all advertisements) you did not state the year of your truck--I have a 51 F5 ex-army truck with a remote booster located under the floor bolted to the frame, if the piston in that booster does not return the brakes will be locked up. When I asked about re-building this booster I was quoted between $500/600 dollars, I plan on removing it from the truck. My 41 1 1/2 ton has the same brakes and since I am not hauling a heavy load they work just fine--in fact I converted to dual master cylinder using a F350 master cylinder from a 68-72 Ford truck