hicrop10 Posted October 21, 2021 Share Posted October 21, 2021 I have 3 old trucks,64 b87,79 r model and a 56 ford f600.My ford is giving me a fit.I rebuilt the vacuum brake booster on it and now the rear brakes lock up as soon as I apply the brakes.I get out of truck and bleed the rears and I can hear the brakes release.Get back in truck start up and depress brake pedal they lock up again.Any help will help. Quote Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/ Share on other sites More sharing options...
mowerman Posted October 21, 2021 Share Posted October 21, 2021 I hadda 55 f600 years ago sorry all I can think of is vaccine boost is bleeding in somehow good luck Quote Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481641 Share on other sites More sharing options...
mrsmackpaul Posted October 21, 2021 Share Posted October 21, 2021 I believe the exhaust on the booster is blocked, dunno what the country is like were you live, but parts of Australia have mud wasps that plug up holes everywhere as quick as look at you I have had this happen several times and is a quick fix Paul 1 Quote Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481651 Share on other sites More sharing options...
Brocky Posted October 21, 2021 Share Posted October 21, 2021 The air inlet hose for the booster comes up into the cab behind the drivers seat.. Check that it is not plugged or crimped??? Quote Brocky Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481656 Share on other sites More sharing options...
Vladislav Posted October 23, 2021 Share Posted October 23, 2021 My guess is the hydraulic hose to the rear axle got plugged due to its age. Inner walls penetrated some components from brake fluid during the years. It probably didn't even pass the fluid before you improved the pressure with the booster rebuild. Now the pressure is enough for the fluid to go to the cylinders but the release springs are not able to put it back. Been there a couple of times. 1 1 Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481751 Share on other sites More sharing options...
mowerman Posted October 24, 2021 Share Posted October 24, 2021 Doesn’t really sound like a very difficult problem just a matter of finding it…. Bob Quote Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481768 Share on other sites More sharing options...
hicrop10 Posted October 24, 2021 Author Share Posted October 24, 2021 Tks,for all the comments.I’ve decided to go rebuild everything route.Am waiting on a rebuild kit for the master cylinder.Once I get it to move like it should am going to check all the brakes. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481829 Share on other sites More sharing options...
mrsmackpaul Posted October 25, 2021 Share Posted October 25, 2021 Something to remember is that even if everything else is working as it should and the air vent hose is still blocked you will have the same problem if that is the issue Paul Quote Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481836 Share on other sites More sharing options...
hicrop10 Posted October 25, 2021 Author Share Posted October 25, 2021 The air vent is clear. Quote Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481865 Share on other sites More sharing options...
Vladislav Posted October 25, 2021 Share Posted October 25, 2021 The key is you have the rears ONLY locked and the front is Ok. If I have understood you right. Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481866 Share on other sites More sharing options...
Brocky Posted October 25, 2021 Share Posted October 25, 2021 2 hours ago, Vladislav said: The key is you have the rears ONLY locked and the front is Ok. If I have understood you right. Check the rubber hose between the frame and the drive axle????? 1 Quote Brocky Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481877 Share on other sites More sharing options...
hicrop10 Posted October 25, 2021 Author Share Posted October 25, 2021 I just got that hose in will be replacing tonight before all the rain moves in,if not my ass will get wet again. Quote Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481880 Share on other sites More sharing options...
mowerman Posted October 26, 2021 Share Posted October 26, 2021 Hicrop it rained here for a day and a half…. I guess it’s your turn… lol bob 1 Quote Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481893 Share on other sites More sharing options...
doubleclutchinweasel Posted October 26, 2021 Share Posted October 26, 2021 I have had the interior of hydraulic brake lines come apart myself, and they tended to act like a check valve in the line. You could apply the brakes, but they would not release. This is not unique to antique stuff. Had to replace both lines on the front of the wife's '05 Chrysler 300C for the same problem. Those were easy to diagnose, as it used twin-piston calipers on the front. Could push EITHER piston in easily, but it was almost impossible to push BOTH of them in. So, that narrowed it down pretty quickly. Really does sound like a rubber line issue. 1 Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481928 Share on other sites More sharing options...
Vladislav Posted October 26, 2021 Share Posted October 26, 2021 ...A friend of mine drove Mercedes G which leaved the assembly line in 1983. The truck (or should it be called a car?) was driven offroad quite extremely and regulary. It had both interwheel diffs fully lockable with hydraulic controls. Something of a kind of hydraulic clutch control in a car. The master cylinders were installed in the cab's floor with a knob to pull by hand and the service units were on the axles. You have two control lights in the dash which are wired to sensors (switches) in the service cylinders so you see if a lock is in. But only in a case the switch is Ok and the wires solid and the lamp is good and all that is not a must for a 35 yo rig. So the guy fought some deep snow or a clay fully locked and than went on a paved road to go home. His story was he covered nearly 10 km to the moment going something 80km/h and the truck once took aside for a whole one meter but continued to go straight. I don't remember how he count out the matter but the turn out was a hydraulic hose to the front axle diff lock. He just released the nipple and drained a bit of fluid after which the diff went free so he could continue the trip. 1 Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-481933 Share on other sites More sharing options...
mowerman Posted October 31, 2021 Share Posted October 31, 2021 I know it’s off the subject… but it rained real hard here I found 2 leaks in my new steel garage roof I like your plan about rebuilding everything that’s the best way… bob Quote Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-482231 Share on other sites More sharing options...
Brocky Posted November 1, 2021 Share Posted November 1, 2021 Bob, You have to remember that when it is raining it is too wet to go out and fix it and when it is not raining it is not leaking!! 1 Quote Brocky Link to comment https://www.bigmacktrucks.com/topic/68532-non-mack-question/#findComment-482236 Share on other sites More sharing options...
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