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Working on a 26 Chrysler. New front end with disc brakes.


Dan Richardson
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Working on a 26 Chrysler.  New front end with disc brakes.  New master cylinder and pressure regulator.  Rear end is original Chrysler and the wheel cylinders have been rebuilt.  The brake pedal will pump up but when released the brakes  bleed down.  The brake system has been bled several times and there are no leaks. So,  why won't the brakes hold pressure?  My head is bald thinking about this one.  Thanks,  Dan

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I believe what your experiencing is a loss of volume not "pressure". If it "kept pressure" when you released the pedal the brakes would be locked.

 

Did the swap include switching to a master cylinder meant for use with a wheel cylinder and disc type of system? 

 

If not then the master cylinder may not have enough stroke volume to feed all the wheel cylinders and disc brake calipers, thus needing to be pumped to make that volume,....

 

or the shoes and pads have too much clearance, and are wasting master cylinder stroke volume,....

 

or brake fluid is leaking past the cup on the master cylinder piston as it moves down the bore. 

 

Also check the proportioning valve to see if it is holding slight pressure in the rear wheel cylinders like the original check valve in the master cylinder would have for the whole system. 

 

Paul

Edited by PFitz (see edit history)
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As Paul states "or"  "or"  "or" . You are mixing a system that was not designed that way so it is unique to your car the way you designed it. No answers in any factory issued instruction book, manual for the car because it is now "upgraded/updated" . Remember you are on a website where original is the way things are restored. This is a bit like asking someone into modified, street rods etc. how to restore something - it will be guess work , no proven fact. I am not using this as a 'put down' to what you are trying to accomplish , just that what is going on and being discussed here is what was done 80+ years ago, not what someone ( you) wants to make it your way now.  I wish you the best and hope you can get this resolved and it works and is safe  for you and others on the road driving around an near you. .

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  • Peter Gariepy changed the title to Working on a 26 Chrysler. New front end with disc brakes.

Yep, confused me. My 26 Chrysler has no front brakes, and mechanical external bands on rear.

Disk brakes would probably pull the wooden spokes out of the steel felloes.😆

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My model 70 1926 Chrysler has stock hydraulic drum brakes. My mechanic had real issues getting the brakes to bleed out. Even now, I refill the master cylinder with fluid before I ever touch the brake pedal. Even then, they act slow for a couple of pedal touches. I think my problem is because the master cylinder is below the floor almost in line of level with the brake. Has nothing to do with your car, just info for everyone. 

Chrysler Home 2.jpg

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IF the rear brakes really are the original 1926 Chrysler hydraulic brake system Then they are part of the Lockheed 4 wheel hydraulic brake system and has external contracting 1.5" wide brake bands that mounts all the way around the outside perimeter of the 13-7/8" brake drums that is bolted thru the wood spoke rim and rear wheel bearing hub assys. The supply line from the brake reservoir to the master cylinder was 3/8" dia copper tubing.  The distribution lines From the master to the left and right side tees was 5/16" copper tubing. The brake lines to the wheel cylinders were 1/4" dia copper tubing.  I described all that  

so you can see that the original master cylinder(bolted to the side of the transmission) had to supply a Huge Volume of fluid thru those Large brake lines. 

it was truly a High Volume Low pressure system as those original master cylinder didnt put out much pressure. To the points brought up by others - It looks like 

one - there is not enough Volume of fluid, two- a mixing of different type systems, master cylinder, and line sizes. Those old Lockheed systems were very 

difficult to bleed as Wayne stated.  One other important note on external contracting band brakes (I've read several times and been told several times -

they dont work worth a flip in the rain.   If you dont have these old external hydraulic brakes on the car - throw out this rambling reply ! CricketKJ26 

 

 

 

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