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Jeep Liberty/Liberty Diesel Brakes

john81john81 Posts: 60
Keep an eye out and see which SUV's or Trucks (imports) start installing rear drum brakes instead of rear rotor and caliper brakes. It is widely known that drum brakes are more "mpg" friendly, but lack the stopping power of rear rotor/caliper style brakes. I am wondering if efforts of making a better braking system has accidently invited additional heat. Weight, momentum and size determines the style of braking system, this according to most mechanical engineers.
Drum brakes are less costly. They worked OK during the 1950's and 60's when cars were iron tanks with huge engines. So what's so different now, only body shape and lighter materials. Lets go back to rear drum brakes. Any retro-fitted drum brakes out there that I could swap out with my rear brakes. Maybe others might be interested also.
John
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Comments

  • threept82threept82 Posts: 1
    Hi Guys.
    This is my first post and I hope it's not a silly question.
    My wife has a 2002 Jeep Liberty, I purchaced a repair manual for it when I bought it and I'll be darned if I can locate it in my house.
    I need to change a bulb for the break light on rear driver side, I opened the rear door
    and removed the 2 inside screws. Everything seems loose but I can't remove the housing is there something somewhere else I missed to loosen? I don't want to just pull on it for fear of snapping something. Any help would be greatly apprecheated. Thanks.
  • libertyinctlibertyinct Posts: 15
    Threept82,
    What a weird coincendence. I just changed mine myself, and ran into the exact same situation. I had the same worry about snapping of some plastic part off and ruining the tail light for good.
    Here's the solution from my experience;
    The outside (for the driver side brake light, it would be the left hand side of the taillight as you are looking at it) of the taillight is held onto the body by (2) prongs roughly .25 diameter that snap into (2) holes mounted into the body. The prongs are located (1) at the top and (1) at the bottom of the taillight. The best way to remove it is to first remove the two inside screws as you did before. Second, you need something to pry the taillight off. I used a large flat screwdriver, sticking it in at the middle of the taillight between the body and the light. It's important that you work it slowly and gently. I do recommend using a cloth or something to cover over the blade of the screwdriver in order to prevent scratching the body or cracking the light. Thank God, I got lucky and didn't do either.
    Good luck. Let me know how it goes.
  • tqqlintqqlin Posts: 3
    I had the same problem...the trick is to give it a good pull after the screws are out, don't worry it won't break. There are clips that help hold it in tight to the body, they release with a good pull.
  • Stever@EdmundsStever@Edmunds YooperlandPosts: 38,931
    I like rear drums too, but why are drum brakes are more "mpg" friendly? You mean they go more miles before you need to replace the brake shoes?

    Steve, Host
  • john81john81 Posts: 60
    The brake pad is located inside the brake drum. Brake pressure is applied which pushes the brake pad against the inside wall of the drum. There is only one surface which actually makes contact during braking. The caliper, on the other hand applies pressure from both sides of the rotor.
    Now, the rotor is exposed to the elements, road salts and rocks. I am trying to find if this situation exists. Ok, take an ironing board, put some water on it and then slide a hot iron over the wet spot. Steam is created and the iron slides across the ironing board. So, when water is heated to a steam state, it becomes a lubricant (of sorts) and reduces surface friction. Does this happen with rotor/caliper brakes in wet weather?
    John
  • Stever@EdmundsStever@Edmunds YooperlandPosts: 38,931
    Dragging brakes will affect your mpg, but properly adjusted discs or drums shouldn't drag. If they aren't dragging they wouldn't be creating heat (and thus steam).

    Maybe someone over in Stop here! Let's talk about brakes can expound, but I don't why there'd be any difference.

    Steve, Host
  • john81john81 Posts: 60
    Wow! Look at all those brake problems. I have to believe that its a "vendor", because it seems that these problems covers all models and manufacturers.
    Can you change the "temper" of the (rotor surface) outside laminate (which makes contact with the brake pads)? I found an old rotor and discovered the interior is not solid. Rotors warp from heat or the tempering of the steel in isolated areas.
    Even front rotors have problems with heat, warping and causing ball joints to fail. I have noticed this for some 20 years. I had a 1981 Dodge truck that was famous for bad rotors, bearings and ball joints.
    I have to believe its the vendor or there is an monopoly of bad technology in which the car manufacturers are forced to purchase from.
    I can't believe that everyone suffers from just caliper calibration problems. Look at all the recalls, even dating back to the 1980's about brakes. I have to conclude that all rotor brake products were defective, but its "theoretical" functionality and performance "trump'd" its failure quotient.
    Rotors are a "consumable item", which means they are suppose to be replaced. I would like to check the specifications standards for rotors, say made in 1985 and rotors made now. Are the "spec's" the same between the two or have changes been made since then.
    Can a caliper brake pads "weld" themselves to the rotor? This may be an extreme situation, but even if welding does not occur, look at the extreme temperatures which change the chemical temper of the steel surfaces.
    I have to thank you guys at edmunds.com/forum. Everyone can't be crazy if we suspect our brakes are bad. Then the only conclusion I have to draw, its a design flaw.
    John
  • tidestertidester Posts: 10,110
    Ok, take an ironing board, put some water on it and then slide a hot iron over the wet spot. Steam is created and the iron slides across the ironing board.

    In the case of fabric, liquid water (and steam) will remain trapped in the fabric providing a more or less steady supply of steam under the iron. The metal in your brakes is nonpermeable so any liquid water or steam is very quickly expelled.

    tidester, host
  • rreidtrreidt Posts: 15
    I have an '03 Limited with 33,500 miles. I had my brakes checked at a good shop and the mechanic said it looked as though they haven't even been broken in yet-yes he showed me too. I don't think my driving habits are any worse or better than anyone else. Why are mine in such great shape and others with less miles are having trouble--no noises at all-just solid braking. It is got to be more than driving habits too. I live in a four season climate.

    -"Lucky Liberty"
  • john81john81 Posts: 60
    This principle of steam used as a lubricant has been successfully used on steam catapults onboard aircraft carriers since the 1960's. A metalic "shuttle" rides on a wave of steam along a metal track driven by a pneumatic piston.
    Rotors in contact with metal brake pads goes along this same principle. This may be a monentary event, until the metal contacts exceed the temperature limits of water and it all evaporates away as steam.
    So, it steam is generated, we are talking the temperature of boiling point, or 100 degrees C. Now, what are the upper temperature limits in which a rotor can withstand? I am sure many people, if under severe braking have not bothered to check their rotors if such an event happened. They just keep driving.
    So, can rotors reach 1000 degree's. Smoking brakes reflect a breakdown of the hydraulic system and fluid gets on the hot metal. At 1000 degrees, hydraulic fluid is quite flammable. That's why hydraulic lines are metal instead of rubber (or should be metal). Not only worn brakes, but worn gaskets or seals in brake lines could rupture from the radiated heat.
    Anyone who has welded their brake pads to the rotor, I would be interested what temperature reading that would be. Maybe exceeding 2000 degrees?
    All these things are possible.
    John
  • john81john81 Posts: 60
    I have to agree that driving habits cause a huge impact on brake wear. My Jeep Cherokee went 132,000 miles without one brake pad or rotor change. I had a manual transmission, so braking was at a minimum. My 2006 Jeep Liberty also has a manual, no brake problems of any kind.
    I think it would be a good idea, like you said, the technician showed you the brakes. Like a doctor visit, have some visual idea what is happening under the car when you slam on the brakes.
    I don't know of any service shop who would invite customers into the work area, like on a guided tour to examine what is wrong with their car. Unfortunately, what most customers sees is their bill, with the prospect that the problem will reoccur.
    Doctor technician conference - Good idea?
    John
  • Stever@EdmundsStever@Edmunds YooperlandPosts: 38,931
    Great idea; some of the newer dealerships feature glass walls between the customer waiting area and the service area so you can see a little of what's going on.

    You can always ask to see any parts removed during service too.

    Steve, Host
  • john81john81 Posts: 60
    http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml
    Check out this website on brakes, brake characteristics, rubbing, overheating and such.

    Submitting a new electronic braking system based on old technology, magnetic amplifiers.
    Hyraulic fluid, according to the above website, can overheat and boil inside the brake lines creating bubbles.
    So, could I substitute brake lines with electrical wiring feeding a magnetic amplifier. The mag amp might cause the caliper to close when opposing "N" and "S" fields are present thus closing the pads against the rotor. Pads are off the rotor by putting a "N" and "N", same pole charges thus repelling the pads keeping them clear of the rotor.
    The rotor is a spinning iron wheel, so could I use this as a reverse clutch to stop the vehicle via opposing torque?
    The only problem is that magnetic amps need alot of power to create the magnetic fields necessary to stop a vehicle.
    Could incorporate a separate alternator to supply all the required power necessary.
    How difficult would this be? Mag amps can control large servo's, so how hard would it be to stop a car? I'll draw up a skematic and work out the math.
    John
  • john81john81 Posts: 60
    I did the math on the magnetic calipers. My reference was based on normal hydraulic brakes which reaches up to 2000 psi (fluid) during braking and transfers 500 ft/lbs of force onto the rotor via the brake pads.
    In a magnetic situation, I would need a magnetic field, on each wheel's caliper about the size of a large car to produce that amount of force. If you buy a computer hard drive, it says, keep it way from magnetic sources like monitors or large magnets. So magnetics are not very practical and potentially dangerous to you car's computer.
    What I did learn is that "if" a caliper does not have an internal value to equalize the pressure or a faulty equalizing valve, then the hydraulic 1500 psi will be distributed unequally over the rotor. If one caliper plunger sticks out more than the other, so putting pressure to one side of the rotor causing the rotor to bend while its still turning.
    Now, you put on the brakes with 1500 psi hydraulic pressure with 500 ft/lbs going to the brake pads via the caliper, but what happens when you release the brakes? Where did that 1500 psi go to? Does it go back to zero psi or is there some residual pressure left which still causes the brake pads to make contact with the rotor. Then I would think that a hydraulic value was bad. Your maintenance dept has on hand a 3000 psi gage and a 1500 psi gage to test the hydraulic pressure going to the calipers. Now, I would ask, when the brakes are released, how much of that remaining pressure can be called out of tolerance? There should be a valve which creates a negative pressure to pull the caliper plungers away from the rotor.
    Should there be a dashboard light to indicate higher than normal hydraulic psi under no brake conditions.
    John
  • I have replaced my front disc pads twice and rotors once, both by myself. At almost 100,000 miles, my rear brakes are starting to go in my 2002 Liberty Limited. Anyone have pointers for doing such a repair myself...like is it much more complicated than the front brakes?
  • tidestertidester Posts: 10,110
    I would need a magnetic field, on each wheel's caliper about the size of a large car to produce that amount of force.

    I don't know how you arrived at that conclusion but it's not the physical size of the field that matters, it's the size and energy requirements of the magnet that matter (assuming you go for an electromagnetic rather than a permanent magnet!).

    Technically, magnetic fields continue far out into space but they typically fall off very quickly with distance.

    Also, I advise against storing your computer hard drive near your brake pads! ;)

    tidester, host
  • john81john81 Posts: 60
    You should know that magnetic energy is hard to contain because it radiates into space and most of it is lost. So to generate the same amount of force (as in hydraulic brakes) your immediate field would have to be that large, to compensate for any field loss. Not to mention the weight needed to hold those thousands of coils of copper wiring. This was why magnetic amplifiers were ditched in the 60's and 70's because the advent of transistors.
    You know that an automatic transmission is another hydraulic unit. So what if one hydraulic unit is fighting with another hydraulic unit, say in putting on the brakes and forcing the automatic transmission to stop, What are the odds something might snap? One of the common elements is the differential. The automatic transmission is pushing the axle to sustain speed while the brakes are trying to stop the axle. Wow, aren't we having fun with physics!
    So, until another day at science class, keep learning about those FUBAR brakes from Jeep. If they can't figure it out, then they're out of business.
    John
  • john81john81 Posts: 60
    Wow, where did you find this, this is awesome!
    I would have more confidence in motor controlled hydraulic valve rather than a hydraulic pressure valve.
    The main computer would have alot more control in braking input and feedback response.
    I am reading over this website, and I'm thinking its not the weekend do-it-yourself'r. The addition of accelerometers and the various sensors would have to be aligned just right for maximum performance.
    I'm going to find out if someone around here in Southern Ohio or Northern West Virginia sponsors Continental Automotive system.
    If Jeep negotiated a contract with Continental to reconfigure their 2007 models or could retro-my 2006, I would seriously consider driving over to my dealership Service Dept and let them have a crack at it.
    Thanks!
    John
  • caribou1caribou1 Posts: 1,348
    I've read a few lines about this in the past year. Peugeot and Citroen were trying this system on their compact cars. They were using compound (multiple piston) brake jaws.
    There is one thing I would like to find on 4x4 trucks: it's a disk brake directly mounted onto the transfer case. This would be a great deal for those who have to tow and slow down heavy loads because the 4 wheels can spread the braking effort mechanically, and braking before a set of reduction gears calls for less power because this disk would spin faster.
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