brake issues

lacabrera · **Posted:** Wed Feb 24, 2016 3:37 pm

I no this is not just CRD related or maybe? Brake light came on today, had to topup the reservoir bottle. Checked brake callipers and found both rear callipers leaking badly? I know all was ok last time the wheels were off (just 1 week earlier) and now to have both leaking badly. Coincidence? Any suggestions that may have caused this. The callipers had new seals and pistons fitted just over a year ago?

flash7210 · **Posted:** Wed Feb 24, 2016 4:42 pm

I would get completely new calipers this time around.
I just replaced both my rear calipers, about $40 each.

lacabrera · **Posted:** Wed Feb 24, 2016 5:42 pm

flash7210 wrote:

I would get completely new calipers this time around.
I just replaced both my rear calipers, about $40 each.

$40 is a good price, Just ordered Crown callipers, hope they are up to the job.

Drewd · **Joined:** Mon Feb 06, 2006 12:24 pm **Posts:** 902

If you have over 100k consider replacing the rubber brake lines that go to the calipers. I have had two that failed on me and the other two were badly cracked. Do a forum search and you'll see that this issue wasn't unique to my vehicle.

I also had a second brake failure with hard brake line that rubbed against another hose. Never had a brake hose or line failure until I owned a Liberty.

lacabrera · **Posted:** Sun Feb 28, 2016 8:07 am

Just replaced the callipers today, brake lines all look good thanks for the advice drewd. Back up and running, have a 1000 mile round trip planned for next week down to were the sun shines most days.

lacabrera · **Posted:** Mon Mar 28, 2016 6:49 am

I am still having problems with brakes on my CRD. after driving constant for around 200 miles the front left brake decided to lock up on me. Loosened of the bleed screw on the callipers and the brake released. Removed the master cylinder today and all seems to be working ok? Could it be the ABS system causing my problem or brake servo?

flash7210 · **Posted:** Mon Mar 28, 2016 7:12 am

Your front calipers probably need to be replaced too.

On mine, the caliper piston was cracked and missing a large chunk.

lacabrera · **Posted:** Mon Mar 28, 2016 9:51 am

flash7210 wrote:

Your front calipers probably need to be replaced too.

On mine, the caliper piston was cracked and missing a large chunk.

Thanks I did notice a chip on the piston last time I replaced the pads, I recon I will have a new Jeep in replacement parts if things carry on the way they are lol.

lacabrera · **Posted:** Sat Apr 30, 2016 9:01 am

Help required !!! After many hours and replacing parts including today replacing the master cylinder and brake booster I am still having dragging brakes. Finally found the problem being the vacuum pump is producing more of a vacuum than the brake booster can handle. Brakes binding remove the non return valve on the booster and the brakes free up? I have no vacuum gauge but placing a finger over the vacuum hose from the pump and I would say it feels far more than it should be.
My question and I hope some one has an answer is. The solenoid valve that controls the turbo boost dose it also control the amount of vacuum required for the brake booster or is there a second valve to control the vacuum. I have traced the vacuum tubes 2 go through the fire wall and I guess there are for the ventilation system inside the cab. I have also checked the 2 non return valves on the tubes close to the turbo and seem to operate ok. Any help with this gratefully received.

flman · **Posted:** Sat Apr 30, 2016 10:53 am

Try this.

https://dl.dropboxusercontent.com/u/19672761/booster.pdf

flash7210 · **Posted:** Sat Apr 30, 2016 12:10 pm

Try pulling the ABS fuse.
If the problem goes away then it might be the ABS system.

I doubt that the problem is the vacuum booster or the vacuum system.

WWDiesel · **Posted:** Sat Apr 30, 2016 12:41 pm

Never in all my years as a mechanic have I heard of having too much vacuum on a booster! Do not think that has anything to do with your problem.
Most likely problem if brake pressure is building up in a caliper on the front and applying or dragging the pads is the rubber flex hose between the metal line on the frame and the caliper has collapsed internally and is preventing the brake fluid from returning back to the master cylinder. When this happens it acts like a one way check valve!!
As the vehicle is driven, the pads are always slightly touching the rotors which causes the calipers to warm up, as the brake fluid heats up it expands and has to bleed back off internally through the hoses and lines back to the master cylinders reservoir to relieve the pressure. If it cannot return properly, this will in turn slightly apply the pressure to the pads via the caliper and cause dragging and eventual overheating. This is why you saw the pressure release when you opened the bleeder valve!
If the caliper is not sticking; replace the rubber hose connected to it and it should solve your problem....
BTY, this is a common problem on older vehicles as I seen this many times..... :wink:

lacabrera · **Posted:** Sat Apr 30, 2016 2:00 pm

Thanks for the replies. spent an hour trying to sort this problem out, @WWDiesel I do not think is a collapsed hose as its locking up all four brakes and as soon as I remove the vacuum from the booster the brakes release. I tried reducing the vacuum by causing a leak and it just gave me a much reduced booster assistance so your correct its not to much vacuum. I dismantled the old booster to see if I can find any fault but no. Also was looking for any adjustment possible between the master cylinder and the rod inside the booster but no adjustment possible. The brake fluid is just not returning back to the master cylinder because the return holes are closed due to the piston inside is not retracting fully as soon as removing the stored vacuum or loosen the the 2 brake line unions on the master the brakes free up. @flash7210 I have tried it with out ABS with no difference. @flman I have done all the known basic test for the brake booster.
I do on occasions get an over boost code pop up but I would not think its connected.

lacabrera · **Posted:** Sun May 01, 2016 12:17 pm

Just tested my vacuum pressure and its above - 60inch/water @ idle. Any one have a reading so that I can compare? I would like to discount this from my problem and move on to what is causing my brake binding. Thanks for any info in advance.

WWDiesel · **Posted:** Sun May 01, 2016 2:36 pm

You may be on to something; I have seen in the past of a couple of vehicles where the rod between the brake petal and booster/master cylinder was adjusted slightly to tight with no free play in the petal before it starting pushing the master cylinder and this caused all four brakes to apply and not be able to back off. Not sure if our Jeep CRD's have an adjustable push rod or not. Other possibility is something not allowing your brake petal to return to the fully retracted position when you take your foot off petal. See if you can manually pull up on the petal and gain some free clearance?
Keep us posed as to what you find.... good luck!!!

lacabrera · **Posted:** Sun May 01, 2016 4:24 pm

WWDiesel wrote:

You may be on to something; I have seen in the past of a couple of vehicles where the rod between the brake petal and booster/master cylinder was adjusted slightly to tight with no free play in the petal before it starting pushing the master cylinder and this caused all four brakes to apply and not be able to back off. Not sure if our Jeep CRD's have an adjustable push rod or not. Other possibility is something not allowing your brake petal to return to the fully retracted position when you take your foot off petal. See if you can manually pull up on the petal and gain some free clearance?
Keep us posed as to what you find.... good luck!!!

I have completely dismantled the old brake booster. The rod inside has no adjustment. I have taken a close look at the valve mechanism that allows air to enter the rear of the booster loosing the vacuum on that side so the vacuum remaining on the opposite side pulls against the MC and it dose not seal correctly allowing a small amount of air to enter especially with such a high vacuum generated by the pump. Ok on a gas motor with only a low vacuum generated by the intake manifold.
The 2nd booster is 2nd hand and I feel is suffering from the same problem.
I also found out that the part number on the booster has changed? The old number P52128967AA has been replaced with 5134120AA so is it possible that they are known to cause a problem under a higher vacuum and a modified version manufactured.
I have ordered a new booster from Rockauto and hope this sorts the problem.

Hexus · **Posted:** Mon May 02, 2016 10:30 am

JEEP

Just
Empty
Every
Pocket

lacabrera · **Posted:** Tue May 03, 2016 11:49 am

Hexus wrote:

JEEP

Just
Empty
Every
Pocket

Yes every pocket and more :banghead:

lacabrera · **Posted:** Mon Sep 19, 2016 2:50 pm

Finally sorted the brake problem. I am 99% sure it was the brake booster pushing the brake master. Seemed to be worst on hot days? Maybe the rod is slightly to long and was closing the return ports on the master, a couple of tho made a huge difference. Part number has changed during production run for the booster and my old one had the part number that is no longer available.
DAMAGE CAUSED BY FAULTY BRAKE BOOSTER
Both front rotors warped
Front right calliper over heated causing piston to expand.
Both rear calliper seals melted causing fluid leak.

GordnadoCRD · **Posted:** Tue Sep 20, 2016 12:41 am

Something to consider when working on any brake system, and particularly any disk brake system.

ALL Brake Fluid is hydrophilic, meaning it attracts and absorbs moisture. This includes atmospheric humidity, not just droplet water. A small amount is tolerated under normal circumstances, without even being noticed.

The problems begin showing when the brakes begin to heat up. (long downhill braking, heavy traffic braking, anything that starts heating up the brakes, and can be made worse by hot weather) when this happens the moisture in brake fluid suspension begins to turn to vapor (steam), this causes the brake calipers to apply pressure of their own accord, exponentially making the heat problem worse. And more complex. AS the vapor finds it easier to move the caliper pistons, pressure is applied to the pads and discs, rather than pushing the vapor and brake fluid back up through the master cylinder into the brake fluid reservoir. The other thing this does, is the excess moisture that has not yet turned to vapor, when pressure is applied, returns again to free liquid form, and settles to the bottom of the slave cylinders / calipers, which prevents it from being flushed out with a normal brake fluid bleeding, as the bleeders are at the top of the units. Once this happens, the problem tends to return again and again whenever the particular brake heats up. Once enough heat energy is dissipated, the steam returns to liquid, settles to the bottom again, and the brakes release.

I learned of this years a go when a Grumman-GM commercial van kept having front brake locking issues I couldn't duplicate in testing, so I went for a ride with the normal delivery driver. On a long downhill with a full load, suddenly the front brakes began to lock up and he lost solid brake pedal control. By the time he got it pulled over and stopped, both front brakes were locked and even the tires were too hot to touch. I opened the brake bleeder too far and ended up with first/second degree burns from the brake fluid blasting out propelled by steam. We spend the next 2+ hours sitting on the shoulder with the bleeders barely cracked while the water boiled and the steam slowly escaped.

From that time whenever I do any brake work, it includes removing calipers, cylinders, whatever is involved, draining ALL fluid, and replacing with new. I have only had the same thing happen one time since, when I bought a vehicle that had been stored at the beach for 3 years, and drove it home. After changing all the fluid and draining / cleaning every caliper, it never had another such problem to the best of my knowledge.

I'm not saying this IS the problem you are dealing with, but it sounds as if it could be.

brake issues

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