@#$%& Brakes!! - JeepForum.com
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post #1 of 16 Old 08-28-2019, 06:45 AM Thread Starter
Neuner-9R
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@#$%& Brakes!!

Tired of messing with my brakes and need to get them right. '85 disc front, drum rear, manual.

Long story short:
- 2 years ago, original brass proportioning valve was leaking so purchased new one for a shop to install. Had to buy an adapter for the rear brakes to fit what I think was a GM fitting.
- Been having issues with what I think are the rear tires locking up too easily during some braking.
- Week ago, brakes felt soft during commute. Checked MC reservoir and front brake small chamber was overflowing and large rear was nearly empty so took it by brake shop for review.
- Shop replaced main rear flexible drop line from the tank as they believed it was collapsing and sometimes preventing fluid flow. Disconnected MC and tested it, all good.
- Shop said not getting fluid to back (used proportioning valve tool) and believe the newer P-Valve to be bad. I'm wondering if it's really messed up or I purchased a wrong replacement.

I lost faith in the first shop that replaced the P-Valve with other projects and I'm not sure I trust the brake shop fully as the technician sometimes fumbled his description of procedures with the P-Valve.

I've swapped engines, rebuilt transmissions and T-cases but I HATE working on brakes and rather a shop do it but getting low on funds and trying to figure out what to do.

Friend thinks the P-Valve is getting off center and causing rear brakes to not work and then work all of a sudden causing my initial issues. Also thinks that by it getting off-center, along with the collapsed brake line, are causing brake fluid to get pushed to the front with air introduced into the system.

Guess I need to order a new proportioning valve and want to pick up a P-Valve tool as well. Can you verify these are correct for disc-front, drum-rear replacement?

https://www.amazon.com/gp/product/B0...181W8SQO&psc=1

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post #2 of 16 Old 08-28-2019, 07:44 AM
Fourtrail
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Quote:
Originally Posted by Neuner-9R View Post
Tired of messing with my brakes and need to get them right. '85 disc front, drum rear, manual.

Long story short:
- 2 years ago, original brass proportioning valve was leaking so purchased new one for a shop to install. Had to buy an adapter for the rear brakes to fit what I think was a GM fitting.
- Been having issues with what I think are the rear tires locking up too easily during some braking.
- Week ago, brakes felt soft during commute. Checked MC reservoir and front brake small chamber was overflowing and large rear was nearly empty so took it by brake shop for review.
- Shop replaced main rear flexible drop line from the tank as they believed it was collapsing and sometimes preventing fluid flow. Disconnected MC and tested it, all good.
- Shop said not getting fluid to back (used proportioning valve tool) and believe the newer P-Valve to be bad. I'm wondering if it's really messed up or I purchased a wrong replacement.

I lost faith in the first shop that replaced the P-Valve with other projects and I'm not sure I trust the brake shop fully as the technician sometimes fumbled his description of procedures with the P-Valve.

I've swapped engines, rebuilt transmissions and T-cases but I HATE working on brakes and rather a shop do it but getting low on funds and trying to figure out what to do.

Friend thinks the P-Valve is getting off center and causing rear brakes to not work and then work all of a sudden causing my initial issues. Also thinks that by it getting off-center, along with the collapsed brake line, are causing brake fluid to get pushed to the front with air introduced into the system.

Guess I need to order a new proportioning valve and want to pick up a P-Valve tool as well. Can you verify these are correct for disc-front, drum-rear replacement?

https://www.amazon.com/gp/product/B0...181W8SQO&psc=1

https://www.speedwaymotors.com/Speed...BoCVGQQAvD_BwE

Front chamber goes to the rear brakes and rear chamber goes to the front brakes. If they are plumbed backwards, it can cause what you are having happen

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post #3 of 16 Old 08-29-2019, 12:03 AM
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pV2 is correct. Never used a PV bleeder tool, but OK. You may also need the brake tool that holds the PV valve open whilst bleeding, it is a clip that goes on the end.

You could have the lines backwards but they are different fitting sizes, so could only occur if someone changed the brake lines at same time. Supposed to be foolproof but many a village has lost its idiot to work in an off road shop.

Have you adjusted the rear drums? The valve is supposed to move when there is differential brake line pressure i.e. one is leaking. It could also occur if your rear brake pistons were very loose.

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post #4 of 16 Old 08-29-2019, 06:11 AM Thread Starter
Neuner-9R
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Quote:
Originally Posted by BagusJeep View Post
pV2 is correct. Never used a PV bleeder tool, but OK. You may also need the brake tool that holds the PV valve open whilst bleeding, it is a clip that goes on the end.

You could have the lines backwards but they are different fitting sizes, so could only occur if someone changed the brake lines at same time. Supposed to be foolproof but many a village has lost its idiot to work in an off road shop.

Have you adjusted the rear drums? The valve is supposed to move when there is differential brake line pressure i.e. one is leaking. It could also occur if your rear brake pistons were very loose.
I may have described which chamber incorrectly, all I know is that my setup is correct according to two brake shops. I'll have to confirm tonight.

Both shops and myself have adjusted the rear drums and everything internal with the drums has been replaced or reviewed. No leaks in the system anywhere with exception to maybe the collapsed/kinked rear brake line. It's the only place that is suspected of getting air introduced but there wasn't evidence of a leak since the proportioning valve was reluctant to let fluid past. It only trickled. That line has since been replaced.

In my search for bleeding tools, I've seen both the center kind that I posted and the front clip version that you mention. The last brake shop stated they used the one on the front and maybe the center kind which is what made me confused and start having doubts as to whether or not their diagnoses of my PV was correct. Do both tools do the same thing? Are both needed?
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post #5 of 16 Old 08-29-2019, 10:34 AM
OrangeCJ-5
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I have never needed the tool for the proportioning valve. The larger reservoir should go to the disk brakes. The new proportioning valves do not have the correct thread size for the rear line on a CJ and will require an adapter. I just went through that on mine and decided to risk buying a used valve instead of a new one since I didnít want to deal with another possible leak or changing the nut on my new-ish stainless lines.
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post #6 of 16 Old 08-29-2019, 10:46 AM
John Strenk
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Quote:
Originally Posted by Neuner-9R View Post
..

In my search for bleeding tools, I've seen both the center kind that I posted and the front clip version that you mention. The last brake shop stated they used the one on the front and maybe the center kind which is what made me confused and start having doubts as to whether or not their diagnoses of my PV was correct. Do both tools do the same thing? Are both needed?

I never needed the tool either but I'm weird that way. But it does help.

The center one holds the safety valve in position (ic ann move if you are not careful) while the front tool holds the metering system open.


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post #7 of 16 Old 08-30-2019, 06:06 AM Thread Starter
Neuner-9R
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Clarification, I incorrectly stated the mc connections. I confirmed that the front brakes are connected to the larger/rear reservoir and the rear the small.

I do have the step down adapter for the rear of the PV from the last replacement. Hunted it down at a hydraulic supply shop.

I tested the brake/centering switch and there's no light, no current, open circuit so the valve is centered.

If no leaks or no residue found, still wondering how the front got low and introduced air into the system.

If the valve is centered and there is no flow to the rear then a clogged brake line or PV? Is there a way to test the rear main brake line for a collapse or clog?
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post #8 of 16 Old 08-30-2019, 09:22 AM
Fourtrail
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You can disconnect the rear flex line from the axle and the lines to the wheel cylinders and press very slowly and evenly on the brake pedal to check flow to the rear. Be sure to do it very slowly and smoothly so you don't trip the safety in the p-valve. make sure to keep the front chamber full as to not introduce new air into the rear lines.
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post #9 of 16 Old 08-30-2019, 11:48 AM
Spieg8
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If the MC is going bad, it is possible to pass fluid from one chamber to the other. This is what I suspect may be happening.

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post #10 of 16 Old 09-10-2019, 12:24 PM Thread Starter
Neuner-9R
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Update -

Had a different shop review, check everything and they confirmed the PV was bad. Had one with me along with the valve tool and they replaced, bled and adjusted drums. Brakes working better than ever.

I just noticed evidence of brake fluid leaking on the inside of the firewall just behind the dash. Don't know if this was from before or just started. I'm assuming that this means the MC is bad now?
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post #11 of 16 Old 09-10-2019, 08:05 PM
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Quote:
Originally Posted by Neuner-9R View Post
Update -

Had a different shop review, check everything and they confirmed the PV was bad. Had one with me along with the valve tool and they replaced, bled and adjusted drums. Brakes working better than ever.

I just noticed evidence of brake fluid leaking on the inside of the firewall just behind the dash. Don't know if this was from before or just started. I'm assuming that this means the MC is bad now?
I'll refer you back to post #9.

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post #12 of 16 Old 09-10-2019, 09:30 PM
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MC have a habit of being bad. If you are bleeding brakes and depress the brake pedal, these POS can draw in dirt to parts of the MC that were not exposed before. Soon after, they start to leak. You have my sympathy dealing with these systems.

PV do not generally go bad by themselves, they either corrode from old fluid (hence brass is preferable in aftermarket valves) or they operate and stick in position and do not allow fluid to pass and some guy from a village replaces it rather than resets it. hence the need for the tool to keep the pins in position during bleeding. All this is covered in the Factory Service Manual. Not saying it was not a bad valve....

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post #13 of 16 Old 09-11-2019, 08:07 AM
bob4703
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Clean the brake fluid with brake cleaner and watch for it to reappear. Watch BF levels at the same time. When you bleed brakes you always run the risk of splashing.
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post #14 of 16 Old 09-12-2019, 02:41 PM
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When you replace a master cylinder, Do Not press the plunger in more than described in the instructions. Or you will tear the new seals and soon be doing it again.
RN
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post #15 of 16 Old 09-12-2019, 10:48 PM
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Quote:
Originally Posted by RedNeckCorvette View Post
When you replace a master cylinder, Do Not press the plunger in more than described in the instructions. Or you will tear the new seals and soon be doing it again.
RN
Bit difficult as you should bench bleed the new master cylinder and push the plunger as far as you can to get teh air out. This is helped by silicone grease.

The problem arises when you are bleeding an old AND HENCE DIRTY, master cylinder. tears the seals up if dirt gets in.
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