1940 Mercury Rear Brake Locked

FireEngineMike

FireEngineMike

Senior Member
1. I am trying to adjust the brakes on my new to me 1940 Mercury. I bled the hydraulic system and have a nice firm pedal although it engages close to the floor. I decided to adjust the brakes.
2. The front brakes went well and are set so there is just a slight drag when rotating the tire forward.
3. When I followed the setup procedure for the driver rear, it locked. We were unable to make any adjustment to free the brakes. We eventually pulled the hub/drum, played with the adjustments to pull in/down the shoes, and reinstalled the hub/drum. We followed the adjust procedure and tested the brakes on the driveway. Firm pedal, close to the floor.
4. I jacked up the driver rear a week or so later to continue to adjust the brakes. The tire would not turn. I am at the same point as I was in step 3.
Yes, the transmission is in neutral and the parking brake is still released.
I turned the upper adjusters CCW so they should be at minimum position. I have turned the lower adjusters in increments while trying to turn the tire. Still locked.
Thoughts? Suggestions?
 
Have you used the parking brake? If so check that its fully returned to it slack position. Make sure both sides have the return spring and clip on the cable ends ( inside and on the rear parking brake cable )
Another possibility is the flex line for both rear wheels is collapsing. But both rear wheels would act the same
 
You don't turn the upper adjusters ccw.
One goes ccw the other goes cw.
If looking at the back of the backing plate the one at 10 o'clock goes cw. The one at 2 o'clock goes ccw.
Hope this is the problem and an easy fix.
Mart.
 
Mart said:
You don't turn the upper adjusters ccw.
One goes ccw the other goes cw.
If looking at the back of the backing plate the one at 10 o'clock goes cw. The one at 2 o'clock goes ccw.
Hope this is the problem and an easy fix.
Mart.
Click to expand...

583979
 
Mart, I will try your info.
The instructions I have from the late Paul Garrigan via Ken (no last name in my notes) mention CW and CCW only for the lower adjusters which as you know are the anchor bolts.
This is step (2) in those instructions:
"Begin by backing all the way off, the two 11/16" eccentric adjusters at the top of the backing plate until the wheel turns freely." I took that to mean turn the adjusters CCW.

I believe the person I purchased the car from replaced most or all of the components of the brake system. He told me that I would need to bleed and adjust the brakes.

Ggmac, I have not engaged the parking brake. I loosened the adjustment to make sure it was not affecting the adjustment process. The cables are slack. The passenger rear tire rotates freely with no inertia to overcome.

The car came out of a collection in GA and has not been on the road since 2001, I think.

I appreciate any and all suggestions.
 
glennpm, thank you for the Lockheed brake adjustment picture. Now I can see what Mart told me. I will turn the upper adjustment cams to their lowest positions on my next work session.
Since the driver and passenger brakes are mirror images of each other, I assume that the diagram is correct for the passenger side brakes based on tire rotation. Tire rotation is opposite for the driver side so I would think that cam A becomes cam B and cam B becomes cam A with tire rotation being CW. Or am I overthinking this?
The other instructions I have refer to the front (lower) anchor pins on the passenger side rotating CW as they do in insert C and on the driver side rotating CCW. This agrees with my belief for adjusting cams A and B.
 
FireEngineMike said:
glennpm, thank you for the Lockheed brake adjustment picture. Now I can see what Mart told me. I will turn the upper adjustment cams to their lowest positions on my next work session.
Since the driver and passenger brakes are mirror images of each other, I assume that the diagram is correct for the passenger side brakes based on tire rotation. Tire rotation is opposite for the driver side so I would think that cam A becomes cam B and cam B becomes cam A with tire rotation being CW. Or am I overthinking this?
The other instructions I have refer to the front (lower) anchor pins on the passenger side rotating CW as they do in insert C and on the driver side rotating CCW. This agrees with my belief for adjusting cams A and B.
Click to expand...

The diagram is for the left side backing plate view in Xray.
To loosen either the left or right side, back off the adjusters as Mart said, "If looking at the back of the backing plate the one at 10 o'clock goes cw. The one at 2 o'clock goes ccw."
 
Glennpm, Thanks again. A friend and I are going to play with it this evening. The important detail was learning from you and Mart that I have to turn the adjusters opposite of each other.
The big question I have is why the driver rear brake locked up in the garage after I parked the car having done a successful driveway test (solid, but low pedal). I cannot see how any of the four adjustments could have moved by themselves. There is no evidence of the driver rear tire being dragged into the garage after the test. Passenger rear turns freely. It appears that all components are new.
We have an EFV-8 RG#3 event Saturday which will provide an additional opportunity for consultation.
The joy of antique automobiles. I cannot wait for this to be "one of those stories" after a successful conclusion.
 
You're welcome

You mentioned previously that you also made adjustments to the bottom anchor pins, the ones used for MAJOR adjustment. Assuming that you have done nothing else with the brakes, i.e., new shoes or slave cylinders, both of which can cause lockup problems; I suggest this:

- Turn the upper adjustments so they are completely CCW and CW as above
- Now set the bottom pins to their starting position. This is when the two dots on the ends of the pins are aligned, pointing toward each other.
- Tighten the bottom pins now per the procedure above
- Lastly, adjust the top adjustments to a slight drag and then back off slightly.
 
Kurt, you are the winner. We went nuts adjusting all four points and finally used a hand sledge and 2x4 to remove the drum. Studied what all the adjustments did and made everything minimum. Could not install the drum. My friend suggested I press the brake pedal so he could watch the brake shoes. The rear shoe moved. The front shoe did not. The front piston is seized and the end broke off, probably from all our messing around.

1. What is everyone's opinion on replacing the wheel cylinder? Replace just the one or all four? Money is not a consideration so I am leaning toward doing all four.
2. Sleeve the existing or take a chance on buying new? I have a reference to a person who sleeved wheel cylinders for a friend. My friend was happy with the sleeved/rebuilt cylinders. I have no idea if the wheel cylinders have been replaced previously or are original. Any way to tell?
Thank you everyone for your help!!
BTW, I am going to drive my fire engine Saturday to an EFV-8 RG#3 event. Mike
 
Last edited:
FireEngineMike said:
Kurt, you are the winner. We went nuts adjusting all four points and finally used a hand sledge and 2x4 to remove the drum. Studied what all the adjustments did and made everything minimum. Could not install the drum. My friend suggested I press the brake pedal so he could watch the brake shoes. The rear shoe moved. The front shoe did not. The front piston is seized and the end broke off, probably from all our messing around.

1. What is everyone's opinion on replacing the wheel cylinder? Replace just the one or all four? Money is not a consideration so I am leaning toward doing all four.
2. Sleeve the existing or take a chance on buying new? I have a reference to a person who sleeved wheel cylinders for a friend. My friend was happy with the sleeved/rebuilt cylinders. I have no idea if the wheel cylinders have been replaced previously or are original. Any way to tell?
Thank you everyone for your help!!
BTW, I am going to drive my fire engine Saturday to an EFV-8 RG#3 event. Mike
Click to expand...

It's not an easy decision, and depends on the cylinders themselves. These days, "New doesn't always mean better". A few years ago there was a batch of imported cylinders sold with the fluid holes drilled incorrectly that didn't work at all. Reputation still goes a long way towards ensuring quality in auto parts. If you can find quality rebuild kits, that may be a good way to go. Most times, cylinders need only a quick hone and fresh kits to make them like new. Sleeving is best reserved for restoring hard to get cylinders when new ones are not available. There is nothing wrong with a properly sleeved cylinder (I have one as the master on my '67 Corvette), but there are better uses for your money unless the required new items are unavailable.

"Word of mouth" is probably the best way to find out which way to go. I haven't done a brake job in the last 20 years, so I'm no help, but I'll bet there are plenty of folks on here and other forums that have been through it lately and may have some good advice for you. When I did my '51 Ford in 1987, I honed the original "Ford Script" cylinders that were still on it and rebuilt them with name brand kits. The brake system is still 100% today, almost 40 years later.
 
Strange thing I remember from last fall when I bled the brakes. Some of the bleeders took a metric wrench. Is this normal? The driver rear is 3/8" but the driver front is metric.
 
FireEngineMike said:
Strange thing I remember from last fall when I bled the brakes. Some of the bleeders took a metric wrench. Is this normal? The driver rear is 3/8" but the driver front is metric.
Click to expand...

Don't look now, but you already may have a couple of "imported" wheel cylinders. I bought a set of stainless steel flathead headers 20 years ago that came with metric fasteners. After I bought new American bolts, they fit fine.
 
I"m a firm on if it aint broke dont fix it but on the other hand this is an important system. If I were in your shoes and had the rear drums lose already I would replace the rears as the drums are a pain to remove to inspect the brakes for leaks. The fronts I would leave and put a few(100 plus) miles on and check unless problems arose during that drive time. Tim
 
You must log in or register to reply here.
Back
Top