Front drum brake locking up

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egrens
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Front drum brake locking up

Post by egrens »

I have had a persistent problem with the passenger side front drum brakes on my 1965 310 locking up while gently braking and I could use some advice. I have bled the brakes multiple time and double checked brake shoes drag on each wheel. I have torn down each wheel and clean up each wheel cylinders and they seem to be working very well. My gut is telling me that one of wheel cylinders is stuck extended and when I press the brake pedal, it is traveling further than its companion cylinder. I have thought about buying a whole new set of cylinders but that would be very expensive and I do not understand what is the root cause. I think I will put the front end on jacks, remove the drums and watch how each set of wheel cylinders are functioning. Has anyone else experienced this issue? Any advice?
Ed in Virginia
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spl310
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Re: Front drum brake locking up

Post by spl310 »

Try loosening the adjuster on the offending wheel just a touch and try it again
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jr02518
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Re: Front drum brake locking up

Post by jr02518 »

What vintage are the rubber brake likes to the drums? If they are breaking down on the inside, they are acting like a one way valve. Changing the brake fluid at the same time, might solve two issues.

I have too many years of tech inspector on the brain.
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redroadster
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Re: Front drum brake locking up

Post by redroadster »

Have the drums been machined ?.if it sets ....where the shoes set, can cause the iron to rust there and swells the iron closer to the brake material ,also it grabs it too
Last edited by redroadster on Mon Jun 20, 2022 4:27 pm, edited 1 time in total.
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egrens
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Re: Front drum brake locking up

Post by egrens »

spl310 wrote: Mon Jun 20, 2022 8:35 am Try loosening the adjuster on the offending wheel just a touch and try it again
Great suggestion.......gave it a try this afternoon. Rotated nut ccw by 90 degrees and it seemed the same. Tried to rotate further going ccw and wheel locked up. Went back to original setting and tried to rotate cw and wheel locked up. Appears I have less than 180 degrees total rotation so I split the difference (about 30 degrees from starting point) and same lock up. If I do a panic stop I can get both tires to lock up but on a gentle stop, the passenger tire locks up. Still stumped!
egrens
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Re: Front drum brake locking up

Post by egrens »

jr02518 wrote: Mon Jun 20, 2022 12:40 pm What vintage are the rubber brake likes to the drums? If they are breaking down on the inside, they are acting like a one way valve. Changing the brake fluid at the same time, might solve two issues.

I have too many years of tech inspector on the brain.
I replaced all the brake lines about 7 years ago and they still look good. Over the weekend I drained all of the old brake fluid and replaced with new. BTW, I used a new pneumatic power brake bleeder sold by Harbor Freight, worked really well and now have a very firm brake pedal. Was able to evacuate most of fluid going through each bleed valve.
egrens
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Re: Front drum brake locking up

Post by egrens »

redroadster wrote: Mon Jun 20, 2022 1:04 pm Have the drums been machined ?.if it sets ....where the shoes set, can cause the iron to rust there and swells the iron closer to the brake material ,also it grabs it too
I did not have the drums machined as there was little grooving or step in the bore. Have had some rust before and recognize the sound but it cleans up pretty quick after a couple of stops. The last time I inspected brakes and drums was about two years ago chasing this same problem. Cleaned it all up, reassembled and adjusted.....and brake locked up on my first ride. Hmmmmmm.....I am still suspicious of the dual wheel cylinder design....one might be locking up or not functioning though I do remember cleaning bores of the cylinders and the pistons seemed to slide effortlessly. Getting close to pulling that drum off again and inspecting.
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datsun1500
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Re: Front drum brake locking up

Post by datsun1500 »

Swap the drums and see if it still happens. That’ll narrow it down.
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Re: Front drum brake locking up

Post by D P »

I know zero about roadster drum brakes, so keep that in mind. But inspect your shoes and their orientation, if there is a difference between primary and secondary and they are reversed it can cause this.
egrens
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Re: Front drum brake locking up

Post by egrens »

datsun1500 wrote: Mon Jun 20, 2022 8:58 pm Swap the drums and see if it still happens. That’ll narrow it down.
Good Suggestion.....probably going to open to inspect asap, will try that!

Thanks,

Ed
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Re: Front drum brake locking up

Post by roadsterred »

A quick test of the rubber brake hoses is to quickly crack open the wheel cylinder bleeder valve and close it when the drum is locked up. If the drum breaks free, the rubber hose is defective.

If the drum stays locked up, the rubber hose is probably still good.
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redroadster
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Re: Front drum brake locking up

Post by redroadster »

Glazed drum will create a grabbing to or out of round it's not going to hurt to turn the drums , if they are still turnable
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egrens
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Re: Front drum brake locking up

Post by egrens »

egrens wrote: Mon Jun 20, 2022 7:32 am I have had a persistent problem with the passenger side front drum brakes on my 1965 310 locking up while gently braking and I could use some advice. I have bled the brakes multiple time and double checked brake shoes drag on each wheel. I have torn down each wheel and clean up each wheel cylinders and they seem to be working very well. My gut is telling me that one of wheel cylinders is stuck extended and when I press the brake pedal, it is traveling further than its companion cylinder. I have thought about buying a whole new set of cylinders but that would be very expensive and I do not understand what is the root cause. I think I will put the front end on jacks, remove the drums and watch how each set of wheel cylinders are functioning. Has anyone else experienced this issue? Any advice?
Ed in Virginia
Just a quick follow up to my original post.....problem solved but not 100 percent sure what was the root cause but here are my best guesses:
1.) air in the lines.....I probably bled my brakes 10 times over 2 years trying to solve this problem using an assistant and ultimately using a pneumatic bleeder from Harbor Frt. What seemed to work best was bleed first, pump the pedal two or three times and watch for bubbles in the reservoir, then bleed again. Bleeding alone did not seem to get all the air out. The HF bleeder came with a auto feed top off bottle which keeps the reservoir topped off which worked really well.
2.) Discovery of two adjuster nuts on my front brakes. It had been so long since I rebuilt and inspected the guts of the brakes that I forgot there is an upper and lower adjusting nut. Discovered passenger side was tight on one adjuster and loose on the other. Readjusted brake to drum tension on all four wheels to a very slight drag.
3.) I did swap front drums but not sure of the results.

Hopefully this post and everyone's comments will help a fellow roadster fan if they have a similar problem as I could not find any qood info on this site or on the net on Datsun front drum brakes. Take care ya'all!
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notoptoy
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Re: Front drum brake locking up

Post by notoptoy »

Good that you got some resolution! My money is on the uneven setting of the two adjusters. Brake drum adjustment is so critical to proper braking performance, as you could see. It's amazing that something so critical (braking) is set so crudely (slight drag, defined as what exactly??) and no real, solid, defined measurement method is available to get it right the first time.
"When all else fails, force prevails!" Ummm, we're gonna need a bigger hammer here.

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