Intermittent drum brakes failure

[lighiche]

I know, I know, I've heard most of the better and all of the worst jokes about drum brakes. However, two days ago I experienced a hair raising development with the drums on my 1962 IIA 109 Station Wagon and I need some advice.

Going down a fairly steep incline on my way to work, in second, so not more than about 20 mph, I braked just before the stop sign at the crossing of a much larger road as I always do. My brake pedal travel inexplicably felt impeded. With all of my 265 pounds focused on that 3"x6" patch of rubber I glided not-so-serenely right across four lanes of heavy traffic without slowing or stopping. Fortunately I made it.

After shaking for a few seconds I drove forward, depressed the brake pedal sharply and the drum brakes stopped the vehicle immediately, if not quite on a dime as well as they ever have done since being completely refreshed during the Rover's restoration less than a year ago.

Now it's intermittent. Of course I'm cautious and haven't driven the vehicle much more than to get home from work the other day and to test it around the neighborhood. I can go 30mph - not eager to try faster than that right now - step on the brake pedal and the vehicle will stop quickly, smoothly, perfectly. I can ease up to a stop sign at 10 mph, depress the brake pedal, and glide right through the intersection.

Nothing blocks the brake pedal travel. There's been no trauma to the system. The system was completely rebuilt by Lanny Clark less than a year ago. The symptoms are intermittent, more often when traveling slowly. Also, if the brakes fail I can take my foot off the pedal and quickly depress the pedal again and the brakes work like a charm.

Okay all you diagnosticians, what simple thing in an as-new drum braking system could cause intermittent failure?

Thanks.

[LaneRover]

Any chance your brake shoes need adjusting - though that won't account for the difference between going fast and going slow.

Do you have the original single master cylinder and no servo? If so it could be that the seal in the master isn't sealing well - unless you 'stomp' on it. My '65 109 had the single master cylinder system and when I had it in LA once I went to stop and the truck just kept going. After that it was fine. It was soon thereafter that I decided to upgrade to a dual circuit master cylinder and servo because I didn't want the 'no stopping' thing happening to me again!

[lighiche]

Do you have the original single master cylinder and no servo? If so it could be that the seal in the master isn't sealing well - unless you 'stomp' on it. My '65 109 had the single master cylinder system and when I had it in LA once I went to stop and the truck just kept going. After that it was fine. It was soon thereafter that I decided to upgrade to a dual circuit master cylinder and servo because I didn't want the 'no stopping' thing happening to me again!

Yeah, it's dead stock original, and working a treat until this episode. I've wanted to put in a dual servo for some time, looks like it may be sooner rather than later!

Thanks for your thoughts. Now that I can anticipate things it's a bit safer.....sorta....

[LaneRover]

Thanks for your thoughts. Now that I can anticipate things it's a bit safer.....sorta....

Exactly! That being said, I didn't have the regular issue that you do.

To do the dual circuit you most likely have to cut the top of the front wing. If you don't want to do that so that you can put it back to original if you want I would suggest buying a series III wing and swapping the top of the wing. THOUGH that may require drilling out some spot welds. I did it with my ex-military 109 but I wasn't worried about keeping it perfect and replaced the spot welds with rivets. If your is a Lanny Clark rebuild you may want to do it a bit nicer.

You could also look at replacing or rebuilding the master cylinder as it is. Is it still a single circuit? Yes it is but that may not matter if it isn't a daily driver and/or know you have a single circuit system - which people have used for decades. Swapping out the master would be the quickest and the cheapest way of fixing the issue.

There may be a swap to a dual system that I am not aware of that allows you to not cut any sheet metal.