[Terry M. Hunt]

Took my 65 2+2 for a drive recently. Traffic ahead of me was stopped for a red light so I stepped on the brake to prepare to stop about 50 yards ahead of me. Going about 35 so this was no panic stop. If a panic stop is a 10, this was a 4. Left rear wheel locked up. Took me a second to realize what had happened at which point I released the brake for a second, then reapplied it with same pressure as before. LR wheel locked again. Released pedal then reapplied again. No lock up this time and car came to a stop smoothly. Drove to a nearby empty parking lot and tried to recreate the lock up, but could not. From 40 mph I applied the brakes with increasing force. Never got to a panic stop, but several stops at levels 5, 6, and 7. No lock up. Car has 8 lugs, power brakes, new master cylinder last summer, new hard brake lines and brake hoses about 6 years ago. Never had this happen on this or any other of my old cars. Haven’t pulled the wheel off yet. Master is still full of dot 5 fluid and no sign of leaks anywhere in system. What could have caused this?

[Goatracer1]

Pull the wheel and look for something on the brake shoes that should not be there. Axle lube, brake fluid or ?

[Sirrotica]

Leaking rear grease seal will definitely create the condition you're describing. When grease gets on the rear shoes they will lock up, and skid the wheel that is leaking. It may very well be intermitent, and hard to duplicate.

My advice is to pull the brake drum, and look for contamination on the lining. Brake fluid can also cause this condition, but grease leaking is usually the problem.

[mgarblik]

Sirrotica probably has the most likely answer. But a few things you can do to eliminate other items is: Items it can not be in your system. Master cylinder, power booster, flex hoses or hard lines. This is because the flex line is single in the rear and would effect both rear wheels. So the items left are the individual wheel brakes. Look for leaks of brake fluid or grease as mentioned . Smell the wheels when hot. Grease soaked linings will have a rotten burned sulfur smell. Burned brake fluid has a strong bitter smell. A 4-wheel inspection of the brakes should reveal the problem pretty quickly. If there are NO LEAKS brake fluid or grease, then the only thing left that could cause single wheel lock-up is uneven shoe to drum adjustment or extremely weak or a broken spring on the shoes. That is pretty rare. Let us know what you find.


I just re-read your opening post and caught the DOT 5 fluid mentioned. I know there are many people who swear by DOT 5 fluid in these old cars and have anecdotal evidence of decades of success using it in everything. If the fluid is DOT 5.1, that's fine. If your using DOT 5, pure silicone fluid, all bets are off as far as any and all rubber parts swelling, sticking, tearing in these old systems. This can be from the master cylinder to the wheel cylinder cups and everything in between. It's wonderful that DOT 5 fluid does not absorb water but it is absolutely not compatible with old rubber brake parts. I have personally seen wheel cylinder cups swell to double their normal size, master cylinder seals turn to jelly and roll off the piston, and antilock units seize up completely on modern cars. So in your case, with DOT 5 in the system for years, exercise each wheel cylinder with a little pry bar and make sure the 2 pistons feel the same and move smoothly on all 4 wheels and there are no leaks. The compatibility grouping for brake fluid is: DOT 3,4,5.1 all compatible and can be mixed. DOT 5 not compatible with any other fluid and must be evaluated on a case by case basis with the rubber product used. Good luck with it.

[Scott Thelander]

bad wheel cylinder has my vote ...
time to do both sides...
have your original delco morrains restored,,

[6T5 Cat]

I had the same problem once. It turned out to be rust in the wheel cylinders. I. Replaced the wheel cylinders and problem went away.

[1969GiPper]

Originally Posted by Goatracer1

Pull the wheel and look for something on the brake shoes that should not be there. Axle lube, brake fluid or ?

Primary and secondary shoes reversed or both on the same side.

[Terry M. Hunt]

Pulled the wheel and drum. Wheel cylinder and axle seal completely dry, but brake shoes clearly had an issue(see photo attached). Inner edge of both shoes contaminated by brake fluid. Once I saw this, I recalled something that happened last summer when replacing the master cylinder.
While gravity bleeding the left rear I set up the bleed hose and routed it into a small jar while the car was up on my drive on lift. Went inside for lunch and when I came back I discovered the bleeder hose had popped off the bleeder fitting. Fluid had run down the backing plate and about 1/2 ounce was puddled up where the tire was in contact with the lift runway. I cleaned all this up and finished the bleeding process.
I think what I failed to realize was that as this fluid reached the bottom of the backing plate, a small amount was able to curl around the edge of the backing plate. From there I guess it got picked up by the edge of the drum and somehow distributed around the inner edge of the shoes.
Anyway, installed new shoes and all seems fine after a short test drive. Thanks for all the responses.

[mgarblik]

Glad you found and corrected the issue. Does look like the organic shoes absorbed the fluid that unfortunately had leaked on them. That's a quick easy fix!