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inconsistent brakes

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Old May 18, 2017 | 11:07 PM
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inconsistent brakes

hey guys, i've been putting my recently acquired F600 to good use lately, hauling manure, gravel & busted up concrete to washouts etc. anyhow my question regarding my brakes is that occasionally it has a good pedal but most of the time it'll slowly go to the floor and applying the brakes will cause the truck to run rough, especially at idle.

any thoughts or advice? I replaced the line from the manifold to the check valve but it looks to be collapsing somewhat however it does still pass air, I intend to replace it in the morning. anything else I should look at?


thanks!!
 
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Old May 20, 2017 | 09:35 AM
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Have you noticed a heavy white smoke when the truck
"run rough"? Note that the large diaphragm in the vacuum chamber is supposed to be lubed with something like mineral oil. Could yours be sticking?
 
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Old May 20, 2017 | 12:20 PM
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Originally Posted by NoFrod
Have you noticed a heavy white smoke when the truck
"run rough"? Note that the large diaphragm in the vacuum chamber is supposed to be lubed with something like mineral oil. Could yours be sticking?
thanks for the reply, I watched a couple youtube videos after I posted, there is an old army video that pretty well explains how the system works and i'm wondering if maybe my control valve is gummed up / sticky and allowing the atmosphere valve and the vacuum valve to be open at the same time and it puts the truck into an extremely lean condition... my thought is that the vacuum valve isn't closing all the time as sometimes the brakes are great but a lot of times they're marginal at best... that is a good thought about the diaphragms tho. I wish I could find a tutorial on servicing the system!
 
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Old May 22, 2017 | 01:09 PM
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service proceedure?

does anybody know what the procedure is for servicing the vacu-boost on an early 70's f600? at times my brakes are great and other times the pedal will go to the floor and the engine will run like crap, I think that the vacuum valve in the controller is sticking open when I apply the brakes and it opens a direct 1/2" line into the manifold. what do you guys think, any harm in taking the controller off and cleaning it up? I suppose that the worst that could happen is i'd have to buy a whole new assembly...
 
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Old May 22, 2017 | 04:56 PM
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All makers used these boosters. There were many models. This is for a CornBinder, but the basics are the same or fairly close. I didn't watch this so I don't know if it covers the right territory or not.


This includes the famous U.S. Army training video:

Dave's Place - Hydro-Vac Info

A Chevy has to stop too:

Bendix Hydrovac System Overhaul -- A Stovebolt Tech Tip
 
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Old May 22, 2017 | 05:00 PM
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I posted all that above before I realized you had already been to You tube etc. So, I merged the threads so future replies won't duplicate your efforts.

Good luck with it.

I'm sure you've found reman'd boosters available? Might be a more reliable fix than a semi-blind DIY rebuild???
 
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Old May 23, 2017 | 09:23 AM
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thanks for posting the vids! I haven't started searching for a reman unit yet as I would like to see if the vacuum valve is simply gummed up and just needs cleaned and lubed.... all the same i'm not going to be stupid about it either, the truck empty scales at 11300 lbs and I do load the ol' girl down when I use it
 
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