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Brake Issue on BN2

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MikeAH100M

MikeAH100M

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Went for the first ride of the spring yesterday. The 100 ran great until we couldn't avoid one of Pennsylvania's ubiquitous potholes. Front right took a shot and we immediately heard an intermittent metallic noise from the front right. Sounded like bearings to me (had plans to rebuild both front hubs this week) so headed for home, luckily only about 3 miles away. About 1 mile from home, the brake pedal became rock hard but I could still stop the car. When we get into the garage, all 4 brake drums were very hot and the wheels almost locked. After cooling off, the brake pedal softened and the car rolled easily. I am assuming that heat from whatever occurred in the front right caused this issue but any other thoughts on what to look for? Have not pulled any wheels yet.
 
MikeAH100M said:
all 4 brake drums were very hot and the wheels almost locked. After cooling off, the brake pedal softened and the car rolled easily. I am assuming that heat from whatever occurred in the front right caused this issue but any other thoughts on what to look for? Have not pulled any wheels yet.
Click to expand...

Mike--

If all wheels were affected then the problem or cause would have to be in something common to them all unless somehow pressure from the front right somehow transferred back from the right front wheel cylinder to the other three--an unlikely scenario.

Is it possible that when you hit the pothole you also hit the brake pedal hard with your foot and somehow caused the pedal to remain partially or fully engaged? That seems unlikely as you would have been aware of having done so. However it is possible that you stepped hard on the brakes when you hit the pothole and somehow deformed the master cylinder rod and/or plunger and the pressure then transmitted to all four wheels, though why this would have "healed" after your return to the garage I cannot understand.

In any case I would look carefully at the brake circuit, starting with the pedal action and then seeing if the MC is operating properly. As always, please report back and next time take that drive in Maryland where the roads are great!
 
Mike:

The brake actuation rod and brake pedal linkage must allow the master cylinder piston to move back all the way to expose a tiny bleed port that lets the brake fluid return from the wheel cylinders to the master cylinder reservoir. Without the bleed port, the brakes pump up a bit with each actuation until they finally won't release the shoes from the drum.

Make sure the external brake return spring is present and working. If so, adjust the screw so to shorten the rod just a tad. Chances are this will fix the problem. I did have one non-Healey where the bleed port managed to plug up from debris in the brake fluid. If that's the case, you may have to remove and clean the master cylinder very thoroughly to fix the problem.

If the port is open, you can pump the brake repeatedly and the pedal should not pump up.

Bill.
 
Thanks for the ideas. The master seems like a likely culprit. The car goes up on jacks this weekend and I'll let you know the results.
 
The Master Cylinder was the culprit. The return spring missing didn't help either. I could not get the master apart to see what was wrong inside but it did not "plunge" smoothly and got hung up. Decided to pull the hubs while I had the drums off to check the brake lining. Good thing I did, there are no bearing spacers on either front axle. Good time to replace the bearings . . . . there's always something.

Thanks for the guidance.
 
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