XJ6 & XJ12 Series I, II & III 1968-1992

81 brakes

 
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Old 10-28-2014, 02:03 PM
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Default 81 brakes

So new to the jag scene. I have an 81 xj6 and the brakes are really tough to press and are basically worthless at stopping the car. So my question is does the 81 have the pressure accumulator that is known to fail? If not is the issue probably the brake booster?
 
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Old 10-28-2014, 02:32 PM
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the brake booster is easy to test, make sure vac line is hooked up, push brake pedal and start car, if booster is working brake pedal will drop! if booster is dead, its not like manual brakes! its waaaaay harder!!!! Test for vacuum first though!
 
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Old 10-28-2014, 02:33 PM
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Many if not all brake boosters will fail in time. The one in your car is similar to almost all others. They rely on a diaphragm that is encased in the can.


1. The diaphram can leak and as such no assistance in applying pressure to the master cylinder. Hard pedal, lots of push to get any stopping power.


2. Failec vacumn supply. Not connected. Hose leaks. One way valve stuck in closed position, and as such no manifold vacuum available to aid.


3. Have you vbeen losig brake fluid with no outward signs. If so, it may be drawn iontot he engone and burned via a leking diaphragm.


Fix it. Bad brakes can get you into a worls of trouble.


Unlike the old days. My fiorst cars had little or no brakes!! I was a very good defensive driver.


Carl
 
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Old 10-28-2014, 02:38 PM
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As Darren says, my money is on a failed booster. I did that recently.

If you can afford it you might as well change the master cylinder while you're at it. They seem to be mated for life. When one dies the other isn't far behind.
(';')
 
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Old 10-28-2014, 05:22 PM
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OK, the booster may be shot, but a car this old indicates to me that a full brakes overhaul is needed. The car is 33 years old and nothing lasts forever. The rear brakes are the ones most likely to need attention as they tend to be neglected. You can sort out the handbrake whilst you're in there, too !
 
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Old 10-30-2014, 08:50 PM
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The pedal does not go to the floor so I guess the booster is bad. The car also pulls to the right when breaking. Guessing pressure is not being applied evenly.
 
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Old 10-31-2014, 03:56 AM
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Originally Posted by HawaiiJag View Post
The pedal does not go to the floor so I guess the booster is bad. The car also pulls to the right when breaking. Guessing pressure is not being applied evenly.

car pulling to one side suggests seized caliper/s, as mentioned above a full caliper overhaul- ie seals and clean pistons[or replace if they are rusted]
on my 86 i got away with seals/rotors/pads and piston clean on the fronts but the rears were totally rooted and required new pistons and rotors/pads as well as hand brake pads, i got the seals and pistons from British parts UK and the rotors locally on ebay.au
Richard
 
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Old 11-02-2014, 12:45 PM
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The other thing to check is whether the pump runs. Pump the pedal many times with the ignition off. Switch the ignition on, but don't start the engine, you should be able to hear the pump running continuously.

If it doesn't run check the fuses, relays and connectors. On my Saab it was the connector on the brake sensor which had corroded away.
 
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Old 11-02-2014, 01:04 PM
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Anjum:


What pump???


Hawaii:


I wouldn't mess with a caliper rebuild. Very likely that the bores are pitted and therefore, the new seals won't seal.


Get a set of loaded rebuilds from a reputable source.
and, as a preemptive if not current hit, new front hoses as well. Dettiorated hases can cause a "pull".


Brakes are so important, the right way is the only way.


Carl
 
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Old 11-02-2014, 01:41 PM
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My bad, When the op said accumulator I incorrectly assumed he had the later system.
I.e 1989-94 Jaguar XJ6 ABS Anti Lock Brake Pump Accumulator Pressure Switch | eBay.
 
 
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