Brake lock up

Drewl · 05-19-2020, 03:30 PM

Hi all. New to forums so bear with me. I had new brakes and drums installed on our 07 montana. Since then the left forward wheel wants to lock and skid . i checked the adjustment and it seems fine. I slacked off the adjuster and readjusted so there was a slight drag. Went for a tow and no change. Any ideas? Nothing seems amiss inside the drum.

bobbecky · 05-19-2020, 05:51 PM

Maybe the other three brakes are not adjusted correctly and the one locking up is doing all the work.

**chuckster57** · 05-19-2020, 05:55 PM

Do you have a DC amp clamp? If so then find the break away switch. Locate the COLD side. Put the amp clamp on it and pull the pin. Post the results please. It should be 12-16 amps.

Drewl · 05-19-2020, 06:45 PM

I failed to mention that, yes i did check the other brake adjustments as well and all were good.

Drewl · 05-19-2020, 06:47 PM

I do have the amp clamp and will post the result tomorrow. Thanks for that.

bobbecky · 05-19-2020, 06:49 PM

Make sure the Amp clamp is rated to work with DC amps. An AC amp clamp will not work.

**JRTJH** · 05-20-2020, 05:28 AM

Just an "OH NO, I hope it didn't happen" to consider... If "they" lubed the bearings and reinstalled the drums with the old seal, or damaged the new seals on 3 of the hubs when reinstalling them, you could have contaminated brake shoes on those three wheels, making the "one that's grabbing" the only one that's working properly….

Probability: Hopefully close to never... Possibility: It's happened more than once.....

Here's hoping it's NOT your problem, but if the ammeter doesn't show a problem, I'd be pulling all 4 hubs to check.

**flybouy** · 05-20-2020, 06:25 AM

First I'd be returning to the shop. You paid good money I assume and something's wrong. They should correct it.

If you want to eat that money you paid for whatever reason then here's where I'd start. I'd hitch up and drive to an empty parking lot, pull the break away pin, then see if you can pull the trailer.. It should not take more than about 3'. Or you can jack up each wheel and pull the pin and see if you can spin the wheel. Either way you will have full battery voltage available for the break magnets. A wheel spinning freely = no voltage, some resistance could mean contaminated brake linings.

hornet28 · 05-20-2020, 05:50 PM

A faulty magnet can also cause this

Drewl · 05-20-2020, 05:51 PM

Ok so the clamp tester turned out to be an AC only. I did the wheel off the ground with break away pin pulled and found the opposite side rear axle not working. Pulled the drum and found the clips that keep the wire from rubbing the drum had come off or not clipped on. I believe it was the latter. readjusted all brake shoes and have yet to test drive. I have my doubts the broken wire was the culprit, unless with no voltage going to the magnet has that effect. I'll try to test the amps at the break away switch without the clamp tester. Thanks to all who replied.

Drewl · 05-20-2020, 06:20 PM

Other than trying a new magnet at the suspect brake drum I guess you could just swap it to another wheel and see if that wheel locks up. That's regarding the faulty magnet theory.

**flybouy** · 05-20-2020, 06:42 PM

Quote:

Originally Posted by Drewl

Ok so the clamp tester turned out to be an AC only. I did the wheel off the ground with break away pin pulled and found the opposite side rear axle not working. Pulled the drum and found the clips that keep the wire from rubbing the drum had come off or not clipped on. I believe it was the latter. readjusted all brake shoes and have yet to test drive. I have my doubts the broken wire was the culprit, unless with no voltage going to the magnet has that effect. I'll try to test the amps at the break away switch without the clamp tester. Thanks to all who replied.

The whole purpose of the 12v to the "magnet" is to energize it. It's an electro -magnet. The higher the voltage the greater the magnetic force to drag on the vertical surface of the drum. The brake controller adjusts the voltage for the amount of braking force required. No voltage = no breaking, 12v = full breaking.

**chuckster57** · 05-20-2020, 06:50 PM

Last week we had a fiver with no brakes. Amp clamp showed 9.6Amps which told me 1 magnet wasn’t working. Second drum we pulled had a broken wire to magnet. Fixed it and retest showed 14.5Amps, all magnets good. I don’t think 1 magnet not working would cause another wheel to lock up.

trucker LOU · 05-20-2020, 08:02 PM

Hi all, An old school test for brake magnets. with drums off pull brake away pin or have helper manually operate controller. good magnets should hold a 5/8 combination wrench laid across magnet.I hope you get it sorted,looks like we might get some freedom to travel.-----Lou-----

hornet28 · 05-21-2020, 07:56 AM

A faulty magnet doesn't mean it's not working at all just not working properly. Years ago, over 40, I experienced one wheel locking up and it proved to be the magnet wasn't working properly. I can't remember what I did, I may have replaced it or I may have just hit it lightly with some fine sandpaper, My experience your's may differ

jbplock · 05-28-2020, 10:24 AM

Quote:

Originally Posted by chuckster57

Last week we had a fiver with no brakes. Amp clamp showed 9.6Amps which told me 1 magnet wasn’t working. Second drum we pulled had a broken wire to magnet. Fixed it and retest showed 14.5Amps, all magnets good. I don’t think 1 magnet not working would cause another wheel to lock up.

chuckster,

I recently completed my annual 5th Wheel bearing repack and it seems like your test would be a good one to perform at the end to make sure all four magnets are working after removing and replacing all four brake drums. I have a DC Amprobe (Amp Clamp) and was curious where you physically connect your clamp for this measurement. Can I place the clamp around the main positive cable to the battery, then pull the breakaway switch and measure the current (minus any parasitic current with switch off) or, is there a better way to perform the test? Thanks in advance for your insight.

**chuckster57** · 05-28-2020, 11:45 AM

I use the break away, one side is hot and the other goes to the brakes. I use the brake side and then pull the pin.

jbplock · 05-28-2020, 12:02 PM

Quote:

Originally Posted by chuckster57

I use the break away, one side is hot and the other goes to the brakes. I use the brake side and then pull the pin.

Thanks ... I'll follow your lead

Ken / Claudia · 05-29-2020, 07:23 AM

I have been a victim of brand new out of round or warped brake drum on a passenger car just a few years ago. It was on a rear axle and locked up when brakes pressed hard. It was a non OEM replacement part. Took it back to the shop the following day of the brake job, they said it was the new drum, replaced it and all was good.

Drewl · 11-19-2020, 08:58 AM

Finally figured the wheel lockup thing. Other than the broken wire on the one wheel, the adjustment were not all the same. Talked to an RV machanic who gave me his setup method, which did the trick. You crank up the adjusters till you can't turn the wheel by hand, then slack off the notched adjuster wheel 10 notches. Worked for me. Sorry for delay. Thanks to all who replyed.

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