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Still battling the cj7 soft brake syndrome. Has someone found a good upgrade for 1978 cj7 master brake cylinder? I always have to pump my brakes 2-3 times.
First pump comes up half-way, Second pump comes up firmer, Third pump is just to be sure.
All drums,rotors,and brakes are new. I was told that the master cylinder had been replaced. All brakes are bled. I need a better than stock master cylinder,possibly with a longer throw. Any suggestions?
I have the same problem and I've found that adjusting the rear drums a little tighter usually helps a lot. I go from 2-3 pump brakes to right now stopping brakes just by adjusting the drums. Not sure why the auto adjusters dont do it but they dont. Im thinking that discs are in my future
Go over to IFSJA... there is a guy who sells stuff for cheap that will take care of your brake issues... I can't remember if you have to click wanted or for sale either way, check it out.
Will try to adjust the rear bracks and see if that helps.
Looked at IFSJA on most of the boards (including vendors), but did not find anything about master cylinder upgrades/fixes. If you have anything more specific please let me know. Thanks.
I had the same problem after I replaced all the brake lines. I ended up getting a power bleeder and that solved my problems.
As previously mentioned, make sure you have the shoes adjusted so they just barely drag. The rear circuit does not have a lot of volume to actuate the shoes.
Has anyone seen the auto adjusters work? I have put never sieze on the adjuster bolts and they still don't adjust. Periodically I have to manually adjust. (This is on my S10)
If your master turns out to be bad, replace it with an OEM equivelent. Engineers spent a lot of money designing the system. The only reason to change it is if you change other parts of the system. i.e. add rear disk or larger front calipers. By changing out the master you could open pandora's box.
Hmmm, couldn't find the link either but, I do have this link on my favorites... this could be another route for you.
http://www.ifsja.org/forums/vb/showt...=brake+upgrade
Master Power Brakes does a dual diaphragm booster with upgraded master. Pricey though, around $450. Took a serious look at their system when I did my rear disc setup.
http://www.mpbrakes.com/
Bob
tufcj
Your problem is not your master cylinder. You have air in your system. That is why you can pump up brakes.Quote:
Originally Posted by juggernaught
Get all the air out and you will have good brakes without misspending a lot of money. :sa: :sa: :sa:
I am familiar with the hydroboost system and don't want to go there yet. I already had my brakes bled about a year ago without much change in the peddle pressure. I will ask them if they were "power bled". I usually only have my brakes done by shops that "power bleed", but can't remember.I will look at the rear adjustment, but have been there before and everything seemed to be good.
Lets pretend that everything is in adjustment and that there is no air in the system. Nothing is leaking. All parts are newly replaced (except the m/c). Now, what are my options (except hydroboost) for a m/c replacement? Anything besides a stock unit?
I had D30 with disc brakes from around 78? Someone told me they were Ford. The only way I could get the air out of the front disc's was to take them off and point the bleeder straight up, then bleed them. When mounted, the bleeder was in about the 2 o'clock position and I couldn't get all the air out till I removed them.
I would think that power bleeding would not require you to remove the calipers. But, If I have to manually bleed the brakes that is something I will keep in mind. I think my bleed ports are mounted rather low.
The hydroboost system will not overcome the problem you are having. I am using a hydroboost system and also had to overcome the problem you are having.Quote:
Originally Posted by juggernaught
NPD was right. You may have to remove the calipers to get out all the air. It is a air problem that you are having.
1. are you running bigger tires? If so how bigQuote:
Originally Posted by juggernaught
2. do you have a vacuum booster? If so have you tested it? The buggers tend to leak after a while.
Try the bleeding option first - cheapest of the lot obviously, but didn't overcome my stopping issue (35's). I had pedal pressure, just not enough grip to slow me as quick as I liked.
Disk rear's helped a lot after that. SSBC and TSM both have good $y$tem$ (and I have a set of TSMs for a stock D-20 rear up for grabs :wink: swapped in a D-44, with disks :t: )
You don't want a longer throw on the pedal, you want a larger diameter piston - creates more PSI in the hose. If your not ready for Hydroboost, check into a corvett MC with a 1-1/8" bore, or a dual diaphragm vac booster. BUT, you need to be sure it's not trapped air first.
Thanks.............thats what I needed. Any idea what years of the corvette m/c will work? No vacuum booster so thats out.
Is it really necessary to hold the pin open on the proportioning valve either while hand bleeding OR power bleeding? The books say yes and the mechanics say no. Personally, I have never bothered with the pro/valve while bleeding my other vehicles.
Somewhere in the future rear disc brakes would be nice.
No power brakes? :shock: Maybe that's the first upgrade you should think about. My 77 CJ was a factory disc/drum with power brakes. I'm still running the factory master cylinder with Wagoneer front calipers (dana 44), rear disc, and 37" tires. It stops like it did with the factory 29" tires.
Bob
tufcj
Yes it is important to hold open the pin on the proportioning valve. Here is another tip.
Disconnect the two brake lines that go into the master cylinder and fashion two more lines that will screw into the M/C and turn them up and into the two M/C reservoirs then pump the brakes slowly and do not go all the way down on the pedal. keep stroking like this until no more bubbles come. Then connect the original lines. You should see a lot of difference.
Tufcj...........I just don't have a vacuum booster (nothing between the m/c and the fire wall).
ORC.......If I have someone power bleed my system, do they still need to open the proportioning valve? So far you are the only person telling me (besides the book) that it is mandatory to open the p-valve while bleeding.
I have made an appt. to have them power bled on Thur. morning along with checking the rear drums. I did not ask this guy about the p-valve.
This is one of those issues that has plagued me for a couple years. I would like to put it to rest. I somehow doubt that I am the only one with this issue. But I am very thankful for all the solid advice.
The vacuum booster (the canister between the firewall and M/C) is what makes "power brakes". the vacuum booster assists you in applying the brakes, without it, it's entirely pedal pressure with your leg.
I agree that the rear drums being out of adjustment could cause a low pedal that will pump up.
Have you checked that the correct lines are connected to the right place on the M/C? Generally in a disc/drum setup, the larger reservoir is the front brakes.
Bob
tufcj
Are you ruling this out? I wouldn't if I were you.Quote:
Originally Posted by Old Rugged Crosser
I am aware that the vacuum booster is for a low rpm boost to the brakes. But, if air IS in the line I need to remove that first.
I am not discounting the propotioning valve....my question was "Do you need to open the p-valve while performing a power bled? I would like to know if it is absolutely necessary. My limited understanding of the p-valve is that it is always "open". Am I wrong?
I never have on ANY of my trucks, from the M38A1, Land Cruiser to Chevy K15, to any of my Jeep Trucks (CJ, YJ, SJ's). Bleed through it. Start with the furthest wheel (right rear) and work up.Quote:
Originally Posted by juggernaught
Here is why you should keep the P. valve open:Quote:
Originally Posted by Mudrat
The P. valve restricts the pressure on the rear brake system. You do not want the front brake system to dictate how the pressure is applied to the rear. Same with the master cylinder,
if air is trapped in one segment of the plunger the part that has no air dictates how it operates.
To be successful in your bleeding process you must first make sure there is no air in the master first, then on to the rear brakes with the p.pin held open. :sa: :sa: :sa:
Thanks guys.....we will see how it goes thursday with the power bleed.
This is known as "bench bleeding" the master cylinder. There are generally 2 reasons to do it. 1) installing a new master. 2) original master was drained of fluid.Quote:
Originally Posted by Old Rugged Crosser
A power bleeder (basically a vacuum pump) applies a lot of vacuum to the system. With a good seal at the bleeders it will even pull air out of the master and assorted valving. Start at the furtherst bleeder from the master and work to the closest just like with manual bleeding.
I worked on a 79 CJ7 w/ manual brakes with the same problem. The brakes were really spongy and weak. It had 35" tires and all factory brake components. It turned out that the rubber lines had deteriorated over time and were ballooning. We went to S/S braided lines (mostly due to the custom length required for a lift) and braking performance was greatly increased. We also determined that a vacuum booster would be a waste of time. (Even had one in hand from a donor)
I feel that the hydro-boost system is grossly over-rated. They add complexity to the vehicle. They leak P/S fluid. And when you get one from the junk-yard they need a rebuild. They have a nitrogen charge that helps the unit maintain the manners of a vacuum booster. And you need a high volume P/S pump from a vehicle equipped with Hydro-boost.
If you are intent on throwing parts at it, get a factory vacuum boster and master for your application. The previously mentioned Corvette master could be used if you have 4-wheel disk brakes.
For 4 wheel disc, I have had good luck using Chev 1/2T masters (early 90's w/ plastic reservoir) and eliminating the Proportional and Residual valves from the system. It requires some modification to the brake pedal linkage so it is not 100% bolt-on. The lower rear PSI of the master combined with the removal of the proportioning valve = just about perfect front/rear bias.
I have a vacuum booster and master from a '83 Cadillac Coupe DeVille for 4-wheel disk brakes. (happened to have one in the weeds) I have a Dana 60 up front (factory brakes) and J20 calipers and rotors (Same as 70's 3/4T Chev D44 brake parts) fabbed to my D70 rear.
I could not ask for much better braking performance with 42" Irocks. I soiled myself the first time I locked them up. Most fun is watching your buddys over heating the steering and not have brakes! (Hydro-boost systems)
There is a lot of brake tech in Internetland but beware, there is also a lot of "tech guru's" offering BS. I can only offer advice on things I have learned trial-by-error.
my $0.02 111!!!
Generally. With the use of a power bleeder this is not necessary.Quote:
Originally Posted by Old Rugged Crosser
I used quite a string of 4 letter words trying to bleed my rear brakes. A power bleeder solved the problem. 3 Years later I was servicing the rear brakes when I noticed I had the calipers on the wrong sides so the bleeders were not at the highest point. After switching the calipers around bleeding was much easier. #-o
Why is it always the most stupid things that I overlook?
O.K..........so sometimes I'm a little slow. Got the brakes power bled. He said some air did come out. Brakes are firmer now with a much better feel. Then I realized that DUH! I don't have power brakes.
Never really gave it much thought as I have always had many other mechanical jeep projects going on. I think I always assumed that because I had disc calipers and power steering, that I had power brakes also.
I did come across a NAVAJO BRAKE setup that looks just like the ticket when I get ready to swap to the power set-up.
I did not need to hold the proportioning valve open to power bleed the brakes.
As I have been reading the dialogue about brakes it reminded me to do what I have intended to do for a while and that is to change out my plastic reservoired m/c to the corvette m/c.
As I was bench-bleeding my new m/c using plastic see through hoses run into the reservoirs so I could observe the air bubbles escaping I observed some interesting phenomenon that would have gone unnoticed if the hoses had not been clear.
As I stroked the plunger I noticed that the front brake res. cleared of air very rapidly, pushing out air and pulling fluid back in. The rear brake res. took a lot longer to clear. I also noticed that the rear brake fluid took a noticeable delay before the fluid started moving in the hose. This, it seems, has a function of a hold off valve which delays the application of the rear brakes so that they don't cause the rear end to come around under hard braking.
I was not satisfied that all the air had been pumped out of the rear portion of the m/c as it stopped pumping any fluid through the clear hose when the front portion had been cleared of any air. I then decided to put my brake vacuum pump on the hose and sure enough there was air still in the rear plunger. Air that would not come out using the standard method. This would have caused me lots of trouble as was talked about above concerning Juggernaught's brake problems.
This tells me that using a brake vacuum pump is a very valuable tool when it comes to brake bleeding. Besides it makes bleeding the brakes a one man job. :sa: :sa: :sa:
Thanks..............will look into the vacuum pump. I talked to a mechanic that said they had a setup that used the working a/c unit as a vacuum to bled the brakes.