Complete Brake Failure Due to Brake Switch

Herm sells a dual mc bracket to do away with the single cylinder. It is essentially a copy of the 68-71 CJ bracket. Other then in a museum piece, there simply is no reason to drive a vehicle today with a single-pot master cylinder. Any component can fail at any time. A dual mc is a very cheap piece of insurance.

Would a properly functioning e-brake save your ass if something blows out with a single master set up?

It got me home this time as I was three miles away when the switch blew out. In this case though I was on an isolated road and testing the brakes, e-brake at the ready. In a true emergency you may be trying to avoid a collision, people, a cliff, who know what, and your mind may not be processing "e-brake." When the first switch blew out on me I had people standing too close behind me and I was suddenly rolling downhill backwards toward the crowd. 100% of my attention was on yelling "clear" and steering away from the crowd and to a flat spot without rolling. E-Brake never crossed my mind, though it should have. I was shifting when it blew out, and was in neutral. I could also just as easily have forced it into first or reverse, or even second as I was in low gear and let out on the clutch. Didn't think of that either until after.

I like the dual cylinder mc idea. I wonder though, if the brake switch blows out on one of those will both cylinders fail? My issue is not with the cylinder, but with faulty switches.

Sad but true....
In some cases Crown Automive buys replacement parts from the exact same junk vendors as Ommix Adda.

O.K. so apparently I forgot to mention the dual master cylinder under CJ-3B brake modifications.
I'll cover that oversight later.

That's the general idea.
I know my stock parking brake will skid the rear tires on a gravel road.

The hydralic tubes from the early CJ split bore master cylinder connect to what many guys mistakingly call a proportioning valve.
It is not a proportioning valve it is merely a brass tubing junction.
The proper tubing junction may be very difficult to source.
It is a required component of the split bore master cylinder brake system.
A single brake light switch is installed onto this tubing junction.
If the brake light switch fails 1/2 the brake system still functions albeit without the brake lights.

What has been described, brake failure, is something I'm in the midst of addressing. The most reliable, upgrade solution I've found, so far, by talking directly to experienced experts (classic race car owners/drivers/mechanics who have used this upgrade system) is CH Topping out of southern California.

Ask to speak to Vinny, the son of the owner. CH Topping has been upgrading brake systems on classic cars and active, classic race cars—plus airplanes and motorcycles— for two generations. The customers I've interviewed are more than pleased and offer the kind of specific details needed to make an informed decision.

Greg

I bought my switch at NAPA. They usually have good stuff. They don't list it but the counter guy can match it up.

Greg,
not to put CH Topping down but here on this Jeep forum we are model specif.
In fact whenever it becomes a relative issue we are also vintage specific.
As a forum we know Jeep brakes in minute detail literally inside and out.
To know classic car brakes is one thing.
To know Jeep CJ in full detail from 1941 LRV beginnings to the end (1985) is yet another.

Been there done that twice once in the woods on the trail ,rubber section in the back let loose getting out of the woods was not too bad, but the trip on the road home was more than exciting. the other time it happened in stop and go traffic, just let clutch out and had to apply brakes and wheel cyl. let go . it's amazing how your brain is programmed to believe you are going to slow down when you apply brake and when the pedal goes to the floor it feels like you speed up!! and wham !

G'day all,

I'm still rebuilding my 3B and don't want to go back to the single chamber master. I have the additional issue of being in Australia and my Jeep is right hand drive.

I think I've picked a suitable master for RHD. As the original fit for the single chamber was outboard of the RH frame rail I want the ports to be on the RH side when fitted. I've ordered Dorman P/N M56193, which I think is a replacement for early CJ anyhow. 1" bore shouldn't change the pedal effort and as it's spec'd drum/drum it should come fitted with retainer valves in both ports.

After seeing this post I thought long and hard about the possibility of brake switch failure even with the dual master and came to the following conclusions:

1/ Stating the obvious, if I was going to reinstall the hydraulic switch I'd put it in the rear line, never the front.

2/ We've already accepted this deviation from stock for safety reasons, so why put the hydraulic switch back in at all? Both the switch and the two required breaks/joins in the line become potential points of failure, even if it's only the rear brakes. Of course, we'd all do the double flaring properly but the engineering ideal of minimising the number of potential points of failure in any critical system, still applies.

I'm still working out the neatest way, but either off the pedal or the pushrod I plan to use a standard mechanical plunger switch to run the brake lights. That way I don't need to break into the plumbing anywhere.

I think the simplest way would be to clamp a NC plunger switch to the side of the pedal arm, with the button facing the driver. That way, it contacts the back of the floor when the brakes are released and opens the circuit. The wiring can be cable tied back down the pedal arm nearer to the pivot point then off into the loom.

Potentially, if the stop lights were run as 'earth switched', a watertight switch would be unnecessary and a good quality burglar alarm pin switch would do. It only needs to earth the circuit for the lights to come on.

Using an insulated, watertight switch this should also work with the single chamber system - install a solid plug into the back of the master and get rid of a potential failure point.

A plan at least, but I'm still months away from trying it!

I happened to mention this thread to an ex: army mech. I told him that I also had a hydraulic switch fitted my CJ340. (sorry the picture is a little blurry).

His advice was if worries you that much replace it with a standard “T” piece and go electric on the peddle. Couple that with a dual system and the “no brakes at all” situation disappears....we hope!

There is a brake related chat going on here which goes to show, be it stock or up-grade there's always plenty to chat about. I mention this purely because our 340's unless converted are RHD.

Check out doug's armoured jeep. Pureists, I suggest you don't linger otherwise you'll end up poppin' Prozac like tic-tac's.

http://www.mahindra-register.org/viewtopic...&p=11458#p11458

Original poster back again with another update. After the 2nd Crown switch failed I called KW and they had no suggested course of action. They refunded my money and I called Walcks. Walcks also sells Crown, but also had another brand, so I ordered one of each.

I installed the Crown first, took it straight to the dirt road and tried a panic stop. Straight to the floor. This one actually blew the entire end out of the switch. Switch was still mounted on the MC, the terminal end was dangling from the wires.

Back to the garage to install the other brand. This one has male pins on it and comes with a set of female contacts to crimp to the wire, meaning I'd have to cut off the males on the wire and re-terminate. I left the end cap for the Crown switch dangling as that way I could drive the Jeep without hot wires hanging loose, and took it to the dirt road.

10 hard lock-up slams in a row, no issue. So I cut off the male contacts on wire and terminated the females. Now I have brakes and brake lights.

Sorry, I don't know the brand. It was shipped in an unmarked bad. Ticket says Wends.

I looked up Crown and called them to discuss. I got a call back from a VP of Marketing, who promised to have quality call me. No call from them yet.

I replaced my pressure switch last winter due to elec contact failure, not because the end blew out. I searched and finally found one at Oreilys Auto Parts and it is a Borg-Warner part, works fine. Side note: my rebuilt engine, and rebuilt tranny are ready and should be back in the jeep some time middle of next week. Knowing the brakes are okay, I can refocus my attention to the the other rebuilt parts as I drive.