Master Cylinder And Brake Help

Looking to get some help with my brakes. They went super soft and squishy today. I have been reading about the different parts and where things might be going wrong. I am looking replacing the master cylinder but I am getting confused on what I should by. I have read that it is a dual reservoir master cylinder, is this correct? Also what is the difference between the many online? Some posts say 3/8" bore. I need to somehow convert 1/2" to 3/8"? Is this true? What wheel cylinders are recommended? What products or replacements would work for what I'm trying to do?

 

It would help a lot if you said what year your Jeep is. Mine is a 1964 CJ5, it has the stock single stage master cylinder, and I am thinking of changing it to the duel system on it for safety reasons.

 

have you checked to make sure no wheel cylinders are leaking and master cylinder is full
now if it's a V6 it would be a dual master cylinder
most auto stores will tell you they have a replacement , most are wrong for earlys
amazon sells one . that's correct
Amazon.com: Crown Automotive J0945556 Brake Master Cylinder: Automotive

 

My Jeep is pretty stock '71 CJ5.

 

Check and/or replace the flexible lines. If they are original, they can rot or get soft, and may cause a squishy pedal due to them expanding under line pressure.
If you go this route, I recommend USA made replacements such as Wagner brand.
-Donny

 

Thank you for the help.

 

Not necessarily, I have a 1965 with an original V6 and an original single master cylinder.
Although all 1971 with a V6 may have dual master cylinders
I purchased a rebuild kit and it was easy to install and fixed my problem.
I will be going the dual master upgrade for safety reasons but have more issues to resolve first.

 

Going "squishy" suddenly? (A soft spongey pedal?)

Sounds like the m/c was allowed to get too low on brake fluid, and now has air in the lines. Need to bleed the system.

 

I believe the change to dual chamber master cylinders on the V6 equipped cj5's occurred in 1968 or 1969.
My '69 is dual and the '67 I had was single. I am looking to replace the one on my 1971 with the o.e.m. style part.
Amazon or Kaiser-Willys .But first I am going to see if I can rebuilt original unit if parts are available.

 

While on master cylinders, anyone have the size of the square nut for the master cylinder? 65 CJ single.
Thanks,

 

You mean on the cap? IIRC, it might be 1". Go easy - they are hollow zinc, and hard to find.

 

Thanks for all the help. Changed the master cylinder and the rear wheel cylinders. I bought the master cylinder from 4 wheel parts. They price matched it for $120. I got Crown Automotive J0945556. It fit perfectly, was 3/8 bore so the existing break lines for perfect. The old one was so corroded that one cylinder did not even drain when we detached the brake line.

I replaced the to rear wheel cylinders with Dorman W37090 and W37089 that for great. Not so much luck with the Dorman front wheel cylinders. Just cleaned the old ones really well and put them back in there. Does anybody have a recommendation for new front wheel cylinders that are good and actually fit? The front seemed to sit to low and the pins sat at a vertical angle instead of straight horizontal to push against the drum. No bueno.

Any ideas on good front wheel cylinders is greatly appreciated.

 

The change to dual master cylinder occurred in 1968 (IIRC) and was a federal safety requirement for all vehicles.

 

I think I can confirm that '68 was the first year of the dual master cylinder then, as my '68 was pretty original and has the dual master cylinder. Had a heck of a time trying to find the correct rebuild kit, so I ended up ordering a replacement MC.