ducman491 Posted May 20 Share Posted May 20 Good Morning! I'm having an issue with the brakes gradually locking as I drive and they get hot. Someone suggested that it may be the flexible lines degrading over time so I've replaced those and completely drained, refilled and bled the lines all the way around. This car is 4 wheel drums and it has the original manual master cylinder. I'm thinking my next step is to replace the wheel cylinders and the master cylinder with a modern unit with separate front/rear reservoirs. Has anyone experience this and what should my next course of action be? Also, does anyone have a recommendation for sourcing the parts for this? Thank you Link to comment Share on other sites More sharing options...
old-tank Posted May 20 Share Posted May 20 Check that an exhaust pipe is not near or touching a brake line. Loosen the shoes a few clicks. Seems that something is heating the brake fluid and expanding it. 2 1 Link to comment Share on other sites More sharing options...
EmTee Posted May 21 Share Posted May 21 21 hours ago, ducman491 said: I'm thinking my next step is to replace the wheel cylinders and the master cylinder with a modern unit with separate front/rear reservoirs. The issue isn't the single reservoir master cylinder design. The problem could still occur on a dual-circuit system. Which wheel(s) are locking? Are all four wheels dragging, or is it limited to one or two wheels? If the problem involves all four wheels, then the master cylinder or the brake pedal linkage to the master cylinder are suspect and should be investigated. 2 Link to comment Share on other sites More sharing options...
ducman491 Posted May 21 Author Share Posted May 21 It feels like just the rear which made me think it was the flexible like that fed them. I'm going to try adjusting them a bit and see if that helps. Thank you! 1 Link to comment Share on other sites More sharing options...
JohnD1956 Posted May 21 Share Posted May 21 On 5/20/2024 at 11:26 AM, ducman491 said: Good Morning! I'm having an issue with the brakes gradually locking as I drive and they get hot. Someone suggested that it may be the flexible lines degrading over time so I've replaced those and completely drained, refilled and bled the lines all the way around. This car is 4 wheel drums and it has the original manual master cylinder. I'm thinking my next step is to replace the wheel cylinders and the master cylinder with a modern unit with separate front/rear reservoirs. Has anyone experience this and what should my next course of action be? Also, does anyone have a recommendation for sourcing the parts for this? Thank you Please don't be insulted but that is like when people put a pusher fan in front of the radiator cause an engine overheats. It may feel like a solution but no motor vehicle engineer ever designed a car that intentionally has brake problems. Is there a return spring on your brake pedal? Check if it is broken. Is there an adjustment procedure for a brake pedal return? Try it. Have you re-centered the brake shoe anchor pin? Is the parking brake adjustment too tight? 1 Link to comment Share on other sites More sharing options...
Marty Roth Posted May 21 Share Posted May 21 I had the identical problem on my 1937 Roadmaster! Each time I drove 30 miles, I had to bleed a bit of brake fluid from the farthest wheel cylinder and drive another 30 miles. Expert rebuilt my master cylinder 3 times, but the problem continued ! Turns out - someone, before I bought the car, has incorrectly assembled the master cylinder with a slotted and cupped washer on the wrong side of the plunger rod pushing the piston. This didn't allow the piston, when retracted, to completely clear the passage, and not allowing all brake fluid to return to the reservoir - and eventually the brakes didn't completely release, and then locked up! Find an original schematic of your master cylinder, and reassemble it properly - That solved my issue, and could solve yours. You don't need a dual cylinder. 4 Link to comment Share on other sites More sharing options...
ducman491 Posted May 22 Author Share Posted May 22 (edited) 2 hours ago, Marty Roth said: I had the identical problem on my 1937 Roadmaster! Each time I drove 30 miles, I had to bleed a bit of brake fluid from the farthest wheel cylinder and drive another 30 miles. Expert rebuilt my master cylinder 3 times, but the problem continued ! Turns out - someone, before I bought the car, has incorrectly assembled the master cylinder with a slotted and cupped washer on the wrong side of the plunger rod pushing the piston. This didn't allow the piston, when retracted, to completely clear the passage, and not allowing all brake fluid to return to the reservoir - and eventually the brakes didn't completely release, and then locked up! Find an original schematic of your master cylinder, and reassemble it properly - That solved my issue, and could solve yours. You don't need a dual cylinder. That's an interesting possibility but I don't think it would be the same thing since I don't need to crack the master or drain any fluid. After letting the car sit for a bit things cool off and then it's fine for a short drive. I'm leaning toward things being out of adjustment. It's certainly something to look at for sure. Probably not a bad idea to give the master a rebuild anyway. My father had this car for almost 40 years before it passed down to me and I'm not sure the brakes have ever really been gone through. Thank you Edited May 22 by ducman491 (see edit history) 1 Link to comment Share on other sites More sharing options...
ducman491 Posted May 22 Author Share Posted May 22 5 hours ago, JohnD1956 said: Is there a return spring on your brake pedal? Check if it is broken. Is there an adjustment procedure for a brake pedal return? Try it. Have you re-centered the brake shoe anchor pin? Is the parking brake adjustment too tight? Pedal adjustment is fine but the anchor pin and parking brake are a good suggestion. Thank you 1 Link to comment Share on other sites More sharing options...
Ben Bruce aka First Born Posted May 22 Share Posted May 22 ducman, Willie [ old-tank] may be right. Have you recently done repair on the exhaust system? Many years ago, my 1940 exhaust started leaking on the way to work. By the time I reached my work place there were NO brakes. Afterwork, brakes were fine,. Before reaching home, they were gone. I repaired the exhaust and never had the problem return. We, Dad and I, figured the exhaust was heating a nearby brake line enough for the fluid to expand enough for the brakes to drag, causing the drums to expand . Maybe something similar is happening to yours? Ben Link to comment Share on other sites More sharing options...
EmTee Posted May 22 Share Posted May 22 Did you check the condition of the old rear brake hose after removal? If it was decomposing internally it's quire possible that debris from the hose has contaminated the rear wheel cylinders causing them to stick/drag. Bleed some fluid from the rear cylinders and note the color/condition. Even if it looks OK, I'd still rebuild or replace the rear cylinders to make sure they are good. Link to comment Share on other sites More sharing options...
NTX5467 Posted May 22 Share Posted May 22 The only time I've seen brakes self-apply (fully) was when a quick lube place put the wrong fluid in the master cyl to top off the fluid level. As the customer drove, the incorrect fluid caused the rubber sealing gasket on the master cyl to swell, applying pressure into the brake system with no pedal movement. Eventually, the car stopped on the side of the road, unmovable. When the top of the master cyl was removed, the seal had expanded to about three times its normal size. Took a complete new master cyl and brake calipers and hoses to get it fixed. You mentioned the brakes had been bled, but with which brake fluid? Just curious, NTX5467 Link to comment Share on other sites More sharing options...
ducman491 Posted May 22 Author Share Posted May 22 10 hours ago, Ben Bruce aka First Born said: ducman, Willie [ old-tank] may be right. Have you recently done repair on the exhaust system? Many years ago, my 1940 exhaust started leaking on the way to work. By the time I reached my work place there were NO brakes. Afterwork, brakes were fine,. Before reaching home, they were gone. I repaired the exhaust and never had the problem return. We, Dad and I, figured the exhaust was heating a nearby brake line enough for the fluid to expand enough for the brakes to drag, causing the drums to expand . Maybe something similar is happening to yours? Ben Hey Ben! I haven't done any repairs to the exhaust recently but I did notice that there is a small hole in the muffler while I was underneath replacing the flexible lines. Didn't seem to be near enough to the rear brake lines when I noticed it but to be honest I wasn't looking very critically at it. I'll put a better eye on it when I get under it this weekend. Thank you! Link to comment Share on other sites More sharing options...
ducman491 Posted May 22 Author Share Posted May 22 3 hours ago, EmTee said: Did you check the condition of the old rear brake hose after removal? If it was decomposing internally it's quire possible that debris from the hose has contaminated the rear wheel cylinders causing them to stick/drag. Bleed some fluid from the rear cylinders and note the color/condition. Even if it looks OK, I'd still rebuild or replace the rear cylinders to make sure they are good. The old lines were a bit soft it seemed. It's entirely possible they were the original lines so I wasn't really shocked by that. The fluid I bled out seemed to be clean but who knows. I don't think it would be the worst thing in the world to rebuild/replace the wheel cylinders but I'll try adjusting things first. Thank you Link to comment Share on other sites More sharing options...
ducman491 Posted May 22 Author Share Posted May 22 1 hour ago, NTX5467 said: The only time I've seen brakes self-apply (fully) was when a quick lube place put the wrong fluid in the master cyl to top off the fluid level. As the customer drove, the incorrect fluid caused the rubber sealing gasket on the master cyl to swell, applying pressure into the brake system with no pedal movement. Eventually, the car stopped on the side of the road, unmovable. When the top of the master cyl was removed, the seal had expanded to about three times its normal size. Took a complete new master cyl and brake calipers and hoses to get it fixed. You mentioned the brakes had been bled, but with which brake fluid? Just curious, NTX5467 I bled the whole system with DOT4 fluid since it was completely empty after replacing the lines. If I've buggered this up with DOT4 what would you recommend I use after rebuilding everything? Link to comment Share on other sites More sharing options...
NTX5467 Posted May 22 Share Posted May 22 I don't know that DOT4 would hurt anything, just that the OEM spec Delco fluid evolved into DOT 3. Enjoy! NTX5467 1 Link to comment Share on other sites More sharing options...
Bloo Posted May 22 Share Posted May 22 Dot4 mixes with Dot3 (and Dot5.1) just fine. The higher number indicates a higher boiling point, but all are glycol of some sort. It is Dot5 Silicone that you should probably never try to mix. 3 1 Link to comment Share on other sites More sharing options...
60FlatTop Posted May 23 Share Posted May 23 Owners have been switching to silicone fluid for close to three decades now. And very few have documented the change because their memory is so good. Of course when a car changes hands there goes the memory. At the club tech meetings I used to do a demonstration of how to test for DOT 3/4 or silicone. Take a regular coffee cup saucer and pool at little water in it. Then take a sample from the car. Tapping off a bleeder is best since the reservoir is easy to foul up. Put a couple drops of the sample into the water. If the sample is DOT 3 or 4 it will mix into the water and look a bit milky or spread out. If the sample is from an older forgotten silicone conversion it will bead and tend to bounce and roll across the surface of the water. Then you know for sure. I still have a half pint bottle of silicone fluid if I get pressed into entertaining. Practice on your own and be "Mr. Wizard" at your own meeting. Great entertainment. 1 Link to comment Share on other sites More sharing options...
Frank DuVal Posted May 26 Share Posted May 26 Yes, Bernie! I try to label any conversions I do for other people, but not so 100% on my own vehicles. I better fix that....❗ I can feel the difference between DOT 5 and the others, since I use both in different vehicles. Or, put an Xcelite screwdriver handle into the fluid, those acetate handles get weird in DOT 3!🤣 I learned that back in high school, being an electronics guy and using the same screwdrivers when working on cars.👍 1 Link to comment Share on other sites More sharing options...
60FlatTop Posted May 26 Share Posted May 26 The non-destructive sample in a saucer could eliminate a common problem. If you took that wonky handled screwdriver and put it in a hidden drawer in the farthest corner of your garage a day would come when you were under the car working. You would ask a visitor to reach over on the bench 3 or feet away and hand you a screwdriver. After a very long wait they would hand you that damaged screwdriver. You know that little whiny voice they use when they ask "Gee, your tools are broken. You should get some new ones". While they stand right there next to an array of perfectly good ones. How do they do that! 1 2 Link to comment Share on other sites More sharing options...
ducman491 Posted May 28 Author Share Posted May 28 Just to wrap this up. I was able to make some adjustments on the rear brakes and that seems to have stopped the heating and binding issue. I did notice a bit of weeping on one of the wheel cylinders so I'll be replacing that shortly. Thanks to all who provided some feedback. 3 1 Link to comment Share on other sites More sharing options...
EmTee Posted May 28 Share Posted May 28 5 hours ago, ducman491 said: I did notice a bit of weeping on one of the wheel cylinders so I'll be replacing that shortly. Peel-back the dust covers on each end of the cylinder and look inside. Any moisture and/or accumulated 'mud' is bad and grounds for cylinder rebuild or replacement. 1 1 Link to comment Share on other sites More sharing options...
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