Brake MC issue and questions Renix

[AKghandi]

I have gotten more than a few Mc's that were bad out of the box.

however I have all new brake hardware on my jeep and SS lines.

I have a squishy pedal too

I had a similar issue on an older subaru that I solved by installing a MC with a larger bore. 7/8 to 1" you had to press the pedal harder but it was rock solid and would lock all 4 like nothing.

Not sure if this applies to you but there are 3 different bore size wheel cyls for the rear of a 90.(according to oriellys) my thinking is there is/was different options for the MC to compensate for the different bores sizes. but over the years they just started making the one option

 

[Ecomike]

Very interesting. I use to have a problem getting the wrong size, wrong diameter shoes out of AZ for the rear drums on the 87 as it is a D-44 axle with a towing rig, limited edition Wagoneer 4x4. I am tempted to replace the drums and rotors again all at once. But shoes and pads are new, weeks old at best. Even the 3 year old stuff only had 2-3,000 miles on them. I am starting to suspect a bad caliper up front. The clamped hose test might confirm this. I locked up the rears today in reverse in panic stop with only 1/3 of the peddle applied , so I must be getting somewhere overall, but have yet to solve the mush problem that acts so much like a defective internal bypass on the MC. Wish there was a way to pressure bench test the MCs.

I like 8Muds idea of clamping the hoses one at a time to localize the problem!!! Glad to hear I am not the only one fighting the bad MC problem, as the first one I replaced was only 3-4 months old and leaked out the rear destroying the Vacuum booster, 3 years ago. Then 4 MCs ago I replaced both at the same time due to that issue. I had a bad rotor, tapered inside to out on the 89 that was way bad, but it overheated the new pad on test drives fast and was obvious, and did not cause the kind of mush I have been fighting. This one acts like OK brakes on the freeway with a light foot, but then the last 1/3 of the peddle does nothing, total mush with less braking on thr last 1/3 of peddle movement, same on 4 MCs in a row now, from two different vendors, Raybestos and AZ Durajunk, unless Raybestos is making Durajunk now, which I doubt?

I am also considering removing the vacuum in a test drive to see what happens as the brake peddle is rock hard with the engine off, and locks each wheel off the ground just fine.

Would the WJ MC work on the stock Vacuum booster?

I have gotten more than a few Mc's that were bad out of the box.

however I have all new brake hardware on my jeep and SS lines.

I have a squishy pedal too

I had a similar issue on an older subaru that I solved by installing a MC with a larger bore. 7/8 to 1" you had to press the pedal harder but it was rock solid and would lock all 4 like nothing.

Not sure if this applies to you but there are 3 different bore size wheel cyls for the rear of a 90.(according to oriellys) my thinking is there is/was different options for the MC to compensate for the different bores sizes. but over the years they just started making the one option

 

[Ecomike]

Update time here!!!

Houston!!!! We have brakes on the 87 Wagoneer now. Well at least working well enough now to drive the beast safely.

I can now toss unruly back seat drives through the windshield using the brakes LOL :sunshine:

Not perfect yet, still a soft peddle with too long a stroke, but not as soft as before and it now has solid rear brakes, better than ever before on any of my jeeps. Tried a new one man brake bleeder kit and some new techniques on bleeding the rears and got some more air out and some solid brake action now in forward and reverse.

Now if I can just figure out to swap my too hard to push clutch peddle on the 85 diesel for the too soft brake peddle on the 87 LOL.

Discovered that running the engine (vacuum booster working), and pumping the brake peddle in fast strokes, hard and fast, no waiting with the bleeding valve open, no opening and closing the bleeder valve and using a new one man bleeder kit (OEM tool brand I think), we were able to get the air out and keep air from getting back in. Now the question is will it hold.

I will work on this some more to try and improve it but for now I think I am close enough to call the problem fixed and driveable) with caution, noting that these old jeep brakes are just not like new car brakes, never were).

The bleeding technique we used today was very fast and gave us immediate results!!!

 

[8Mud]

I put speed bleeders in my rears, found them at a Harley shop for around $6 each.

Sure makes one man bleeds a whole lot easier.

 

[cp2295]

To bleed it on the bench put it in the vise and fill it full of fluid. Let it sit until it starts dripping then grab a Phillips head and push on the piston. Plug the holes with your fingers and then let off of the piston, repeat until no or little air comes out. Throw the mc in the rig (gets kinda messy) and then have a helper hop in and bleed the master by using the lines, bleed it like you would the calipers. Think of the lines like bleeder valves, and do it until u can't hear/see any air come out. Then bleed the system. Start by letting all 4 brakes drip until the fluid is nice and clear, (which would indicate all the old fluid has been pushed out and therefore most if not all the air has too). Then bleed all 4 brakes starting at the RR, Lr, rf, and then the LF. Make sure the adjustment on the rear brakes is good. This can make your pedal feel squishy if the shoes are out of adjustment. U want a slight amount of drag. Click the star wheel up until you hear the shoes dragging on the drum. Then take it a couple clicks further and they should be good. Hope this helps!

X2 on the speed bleeders they have a check valve so all u have to do is crack them open and pump the pedal and keep an eye on the fluid level.

 

[Ecomike]

I put speed bleeders in my rears, found them at a Harley shop for around $6 each.

Sure makes one man bleeds a whole lot easier.

I tried that once, not sure which rigs have them where now LOL. But they did not help at the time.

 

[old_man]

Find a place that has an electrical vacuum bleeder and have them do the system. I built my own bleeder with a medical 'GAST' pump and a mason jar. It works great. I put my wife up front to keep the reservoir filled and I can go around and not only bleed a complete vehicle but completely flush the system in about 10 minutes.

 

[Ecomike]

Find a place that has an electrical vacuum bleeder and have them do the system. I built my own bleeder with a medical 'GAST' pump and a mason jar. It works great. I put my wife up front to keep the reservoir filled and I can go around and not only bleed a complete vehicle but completely flush the system in about 10 minutes.

WOW, I should have thought of that, I have about $10,000 in idle lab vacuum pumps in my lab, and one built just for AC work :sunshine:
I am surprised no one has a simple cheap ($100 to $200) rig like that for sale? Sounds like the perfect solution for a bleeding job that sucks LOL. I wonder if using a spare (used) MC cap with a bleeder valve modification added on top would make it easier?

 

[techno1154]

WOW, I should have thought of that, I have about $10,000 in idle lab vacuum pumps in my lab, and one built just for AC work :sunshine:
I am surprised no one has a simple cheap ($100 to $200) rig like that for sale? Sounds like the perfect solution for a bleeding job that sucks LOL. I wonder if using a spare (used) MC cap with a bleeder valve modification added on top would make it easier?

This thing come to mind but I have never used one.

http://www.amazon.com/Motive-Products-Bleeder-Chrysler-vehicles/dp/B000TYJEXG/ref=sr_1_8?ie=UTF8&qid=1312329636&sr=8-8

 

[Ecomike]

Seen those, heard they are good in general (not sure about that brand) and thought about that, but that is a pressure force feed of fluid which a brake peddle does anyway, in the power stroke (not it return peddle stroke), So it is continuous Not cyclic like using the brake peddle), but it is not a vacuum bleeder like Old man suggested. A vacuum bleed should be far superior I think. And if I am right using it from the MC side might even be faster and work better and conserve fluid. In my case I have bleed mine with about 3 gallons of brake fluid already so I have no need to change the fluid again. Old Mans version would change the brake fluid and remove air which would be better in first time cases. In problem cases like mine the top side might make more sense????

 

[Ecomike]

Moving the discussion to here

http://www.naxja.org/forum/showthrea...#post246284583

Now. I just updated the latest there. It just keeps getting weirder