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Hi Guys,

I was reading WVCharlie's post on Gimme a Break and got to wondering. I'm not interested in changing over to disc brakes, but having a dual chamber MC would sure make the stock brakes safer. I'd prefer to find a dual chamber MC that uses the existing 3 bolt triangle mounting pattern, but I haven't seen any other MCs with that pattern. So my question is...........when did Dodge start making dual chamber master cylinders for their trucks? And did they use that dual chamber MC with drum brakes on all 4 corners, or did the dual chamber MC come out with a disc brake package?

thanks,
bob

Excellent question. I need to change to a dual circuit MC and I hope to put new shoes and brake cylinders in this summer. A bolt in MC would be a plus, if it exists

ZG,

There doesn't appear to be any dual chamber MCs with the same 3 bolt mounting pattern as the stock M37 MC. But thanks to a fellow forum member who PM'd me there is a pretty simple solution. Go to the Builders Blog section and scroll down to the post entitled "Rebuild progress, Thread #2 IT LIVES!!!! PG 18" by Josh. Go to the second page and look at the 9th and 10th picture in the post.........they show a simple adapter plate that uses the stock 3 holes in the running board bracket to attach the plate, and the plate has 2 threaded holes to mount the dual chamber MC. Very clean and easy installation.

I think this is the easiest way to mount a modern dual chamber MC.

regards,
bob

Thanks Bob. I have a line on that MC, but I would have probably drilled the step support. That adapter seems like an easy way to go

ZG,

Continued thought on this subject (probably never a good thing) and I see one potential problem. If you use your truck off-road the modern MCs are vented thru the cap. With the dual chamber MC mounted under the running board, and no hard vent line to topside, water intrusion could be an issue. It doesn't look like Josh addressed that in his build, so I got to think about that for a bit. Of course if yours is a parade truck or a garage queen that won't be an issue..........just make sure to tell the next guy who buys the truck he should stay on-road.

regards,
bob

The dual master cylinder lid is sealed against water intrusion. There is a rubber seal that covers the whole reservoir and allows air to replace the displaced fluid, but it is above the rubber seal, the seal is made with two chambers molded in that unfold as the fluid level goes down as the brakes wear, but no air is admitted into the fluid area, water wouldn't be admitted either.

Bob, I have a newer original style master cylinder in now. I used the breather port as a power bleeder port, with an attachment on the other end for my power bleeder. There are a few shallow streams around here that I cross, so I might extend the flexible line I have in place now to a higher place in the engine compartment. I doubt I cross streams deeper than 2"

Are there any other MCs out there which would be good replacements, and have threaded reservoir caps? They are easier to make bleeder adaptors for

J,

I understand what you're talking about, I have a few of those type MCs around here with the collapsible rubber bladder. That definitely will stop any water from mixing with the brake fluid...........but you really don't water sitting on top of that rubber membrane. This is all probably a moot point unless you really want to go play in the water often. But good conversation.

ZG...........I think the best answer is to hunt around a boneyard looking for the best MC for this application. In the boneyard most hood are already up and the MC is easy to get to. I wish we had a few good yards around here in MD. Back in Jersey they were everywhere when I was a kid. Used to spend many a Saturday afternoon just looking at stuff. Oh well.

regards,
bob

I wish there was a junk yard around here. Closest is probably two hours away. That's why I was asking here.

a friend was sitting on a ferry reading the raybestos Bible and emailed me a possible solution MC2657



if you have a 6x6 mc2842 may be the answer

Looks promising, I need to find a spec sheet for it and see if the mounting holes would align with the original cab mount.

I looked around for more info on MC2657 and found some more pics.....but can't confirm it's a dual chamber. Anybody know for sure?

thanks,
bob

w30bob wrote:I looked around for more info on MC2657 and found some more pics.....but can't confirm it's a dual chamber. Anybody know for sure?

thanks,
bob

Have you looked at the rebuild kit for that master cylinder? The parts in the kit should indicate if it's a dual circuit (since it has two primary outlets, I'd be surprised if it's not, but there's that rule about assuming... )

I couldn't find any info on what rebuild kit MC2657 uses, so I called Raybestos directly. Turns out that MC2657 is a single chamber unit, not a dual chamber. I asked if they had a dual chamber master cylinder that used the 3 bolt mounting and the tech couldn't tell me if they did or didn't. Must have been too hard a question I guess.

The search continues!

regards,
bob

w30bob wrote:I couldn't find any info on what rebuild kit MC2657 uses, so I called Raybestos directly. Turns out that MC2657 is a single chamber unit, not a dual chamber. I asked if they had a dual chamber master cylinder that used the 3 bolt mounting and the tech couldn't tell me if they did or didn't. Must have been too hard a question I guess.

The search continues!

regards,
bob

Bob, I believe the Raybestos rebuild kit for the MC2657 is an MK135. The kit illustration shows two cups, but only one circuit?