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Old 12-28-2014, 04:21 PM
jimmorrison jimmorrison is offline
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Front Drums Sticking

So I've been working on my new J10 project and I've hit an issue that is frustrating me. The issue is that the front drum brakes seem to be sticking/dragging slightly. The rears are free.

Back-Story:
This truck ('76 J-10, 360, T-18) ran and drove just fine when I got it. It had manual (non-boosted) 4-wheel drums that worked...but were scary. So along with some suspension stuff, I added a dual-diaphragm booster, extended/dropped the front soft-lines, and swapped in a new master cylinder while I was in there. The booster is from a newer model and the MC is for a '76 but is the disc/drum power variant, not the original manual style.

Now the brakes have great stopping power but after 20-30 minutes of driving I can tell that something is dragging. Once stopped, I can feel that both front wheels are warm-to-hot while the rears are room temperature. I first thought that perhaps I had adjusted the front shoes too close to the drum thus causing drag and then heat which worsened the drag. So I backed the adjusters way off on both sides. This seemed to fix the problem at first but then after a 20 minute drive I could feel things dragging. The dragging wasn't as bad as the first test drive so I let it sit for an hour or two and things freed back up. I drove another 20 minutes and the same things happened. This time I was at my house so I popped the master cylinder cover for no real reason, put it back on, looked at some stuff, then got back in to park the Jeep. When I pulled into my driveway, the brakes were dragging but not terrible but after looking around for 10 minutes I got back in and the front brakes were on hard. I could still move the jeep but I was really fighting the front wheels.

I'm trying to figure out what this could be. I'm thinking that it could be a faulty re-man master cylinder with a sticky piston problem or it could be something fishy with the stock combination valve. When bleeding the brakes, I had to give the combo-valve button a pretty firm tap with a hammer to get it to move so it definitely wasn't free floating. That said, the brake warning light came on and went off as expected so it seems to be moving somewhat.

Also, while driving the amount of free travel in the brake pedal decreases. When the brakes are noticeably dragging, there is also little or no brake pedal travel required to stop.

I'm tempted to go out and grab another master cylinder but I'm not convinced the MC would cause only the front brakes to drag and not the rears.

Any ideas?
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Old 12-28-2014, 09:00 PM
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Carnuck Carnuck is offline
 
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Can't recall if there is a valve in the line or just the retention valves in the master. First though, I would loosen a bleeder in front and see if it still has pressure. If it does, either both brake hoses are swollen from contamination or the retention valve is swollen. The way to tell is either both sides come loose when you open one bleeder (retention valve) or you have to open both (hoses)
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Old 12-29-2014, 03:18 PM
jimmorrison jimmorrison is offline
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I had a little time today to fiddle with things and it looks like the passenger-side wheel cylinder is holding pressure. After sitting over-night the driver's side wheel spins and spins while the passenger side barely makes one revolution after a good hard spin. Further investigation showed that the wheel cylinder pistons would remain extended after the brakes were released. Opening the bleed fitting released the pressure and allowed the shoes to collapse.

Am I right in understanding that this is likely the result of the soft-line deteriorating? If so, where might I find a new soft line for front drums? BJ's doesn't list any and neither does Advance Auto or RockAuto. Anyone know the specs of the stock hose off-hand?

I'm hoping to upgrade to discs at some point just from a parts perspective but that's a bigger project than I'm looking to undertake this winter.
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Old 12-29-2014, 04:29 PM
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Tatsadasayago Tatsadasayago is offline
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Very possible it's the soft line.
I've had the inner break free and the bulge/fold creating a check-valve of sorts. Old soft lines can do some crazy stuff!
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Old 12-30-2014, 10:40 AM
jimmorrison jimmorrison is offline
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Well, I guess they are the original lines so even if that's not the problem they're worth replacing.

After a little checking it looks like NAPA has lines available so I guess that's where I'm headed.
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Old 12-31-2014, 10:42 PM
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I thought the disc side of the master had a check valve that held the pads close to the disc so they wouldn't be so far away at the next stop.
If so, this wouldn't allow shoe springs to retract the shoes.
Can you get an all drum master for '76?
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Old 01-01-2015, 09:57 PM
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The adjusters can adjust the shoes too tight if the show return springs are weak.
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Old 01-02-2015, 11:48 AM
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Montana Mike Montana Mike is offline
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There is no valve to keep disc brake pads from backing off. More than likely it's your flex lines at each wheel. The inside comes apart and acts as a check valve. I had this happen on my Myers Manx dune buggy with drum brakes. When I removed the flex lines I could not blow through them and they would activate but not release. They should be replaced periodically, normally if you see any cracks on the outside the inside is not good either.
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Old 01-05-2015, 12:51 PM
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If you plan a mild lift in the near future, Chev Blazer (same vintage) hoses are the same but longer.
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Old 01-26-2015, 07:45 AM
jimmorrison jimmorrison is offline
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Better...but not fixed

This winter has been tough for me. The short days and cold garage floor have left little time for me to wrench on the truck so the sticking front brake issue has seen little progress. That is until yesterday when a stomach bug left me unable to go a on bike ride on a 55 degree day in January.

So I changed out the front brake soft lines and bled the system to try and fix the sticking issue. Things are better but now more confusing. After changing the soft lines, the front brakes don't seem to be sticking but the Jeep still feels like something is sticking. Not as bad, but it still doesn't roll freely. On the test drive, a car pulled out in front of me and caused a harder than average stop during which at least one wheel locked-up. Not sure which one. Overall the pedal seems maybe a little touchy.

When I got home after a few miles of city traffic and then a few miles on the hwy, maybe 20 minutes of total driving, the Jeep wasn't locked-down as it was before the hose-swap. I felt all four wheels to try and find a hot wheel or set of wheels and I found that the fronts were fairly cool. The passenger side front was slightly warm, the driver's side was dead cold. The rear wheels however were quite warm.

I'm now considering replacing all wheel cylinders, all return springs, and even the proportioning valve. Does anyone have experience with a similar issue?
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  #11  
Old 01-27-2015, 07:26 AM
mokurt mokurt is offline
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Quote:
Originally Posted by jimmorrison
I'm now considering replacing all wheel cylinders, all return springs, and even the proportioning valve.
Replacing the brake hardware is a good idea if the stuff is old.The spring hardware kits are not that expensive.

Also check the backing plates for excessive wear at the brake shoe contact areas,they can become grooved.
Place a dab of grease at those areas when assembling.
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Old 01-27-2015, 07:48 AM
jimmorrison jimmorrison is offline
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Good advice.

Now I just need time...which is tough to come by these days.
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