Moparts

70 power brake rod

Posted By: Sixt8Chrgr

70 power brake rod - 03/25/20 03:03 AM

I have a 70 AAR and my brakes are slightly dragging. I have installed new rubber hoses all around adjusted the shoes etc. Previous owner installed a new MC and I am not sure that the MC is releasing once the brakes are depressed. Is there an adjustable rod that engages the MC?
My brakes, all 4 will get warm, front brakes warm, left rear hot right rear hot to very hot.

Any ideas?

Thanks
Posted By: Cuda340

Re: 70 power brake rod - 03/25/20 11:55 AM

I believe their is an adjustable rod, It is the rod that goes from inside the booster to the rear of the master, it screws in and out. there should be a little gap, so when you tighten your master the rod doesn't push on the piston engaging the brakes. Make sense? There has to be a procedure in the FSM.

Jeff
Posted By: 71birdJ68

Re: 70 power brake rod - 03/25/20 12:51 PM

I can't remember the exact number, but I think the gap is 20 something thousandth. Do a search people have posted good pictures on here before.
Posted By: Cuda340

Re: 70 power brake rod - 03/25/20 05:43 PM

Originally Posted by 71birdJ68
I can't remember the exact number, but I think the gap is 20 something thousandth. Do a search people have posted good pictures on here before.


That sounds about right. Just make sure when you tighten up the master, it doesn't get harder to seat like the rod is pushing the piston in.
Posted By: 6PakBee

Re: 70 power brake rod - 03/25/20 07:14 PM

This is really what you need but you can get equivalent results with a dial caliper if you are careful.

https://www.classicchevy.com/power-...dg-7EAQYASABEgJSSvD_BwE&gclsrc=aw.ds
Posted By: DAYCLONA

Re: 70 power brake rod - 03/25/20 09:11 PM

Originally Posted by Sixt8Chrgr
I have a 70 AAR and my brakes are slightly dragging. I have installed new rubber hoses all around adjusted the shoes etc. Previous owner installed a new MC and I am not sure that the MC is releasing once the brakes are depressed. Is there an adjustable rod that engages the MC?
My brakes, all 4 will get warm, front brakes warm, left rear hot right rear hot to very hot.

Any ideas?

Thanks



ANY time you replace the master on a power system (even the rebuilt original) you need to check and or adjust the booster's pushrod to prevent low pedal operation or brake dragging, generally the Mopar system needs an air gap between the booster's pushrod and the end bore of the master's rear pushrod piston of .020 minimum, to a max of .060 for proper operation.... As mentioned you can use a set of verniers/calipers to measure the bore depth of the master and the booster's pushrod, do the math, and adjust appropriately...

You also mentioned you adjusted the rears, perhaps you "over adjusted?" recheck the rears for rotational drag on the drum/shoes, engine off, rear jacked up, in neutral... After you check/set the booster's pushrod

here's a few pics..,

Mike

Attached picture booster5.JPG
Attached picture boostertoolch.JPG
Attached picture booster gap.JPG
Posted By: Sixt8Chrgr

Re: 70 power brake rod - 03/27/20 01:08 PM

Guys,

Thanks so much. Will work on this today as I am "sheltered in place" here in NC.
Posted By: Sixt8Chrgr

Re: 70 power brake rod - 04/25/20 08:36 PM

I took the master cylinder off the booster and adjusted the rod so the front brakes are not dragging. But my rear brakes are dragging individually, alternating. I know this sounds crazy, but today I went for a drive, and after about 8 miles checked the wheel heat. The front wheels were fine, but driver side rear was hot. The passenger rear wheel was fine. Jumped in the car drove it another 8 miles or so. Stopped checked the rear wheels and now the passenger side wheel is now hot and the driver side rear wheel is cool. Is the proportioning valve failing?

Thanks for any help.
© 2024 Moparts Forums