XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Confounding Brake Issue

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  #21  
Old 05-11-2020, 09:55 AM
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Originally Posted by JayJagJay

Dude. Do make sure that you run all of that H2O out of the brake system. It's important
Will do. Just to clarify, the only part that was exposed to the washer fluid was the copper line running from the reservoir to the brake pump. The line was disconnected from both the reservoir and the pump when I ran the washer fluid through it. I let it air dry and then ran a liter of break fluid through the line to flush out any remaining washer fluid.
 
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Old 05-11-2020, 10:01 AM
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Originally Posted by Greg in France
Not yet! proceed as follows, one side at a time:
  • jack up car
  • remove one rear road wheel
  • undo the pin that secures the bottom of the shock to the lower wishbone arm; NOTE what washers go where
  • support the lower wishbone/hub and drive the pin out towards the front from the rear using a brass drift
  • the shocks are now free at the bottom
  • at the top there is a bolt holding each shocker, it goes through a bracket and through the cage.
  • undo the bolt, one spanner on the fixing on the outside the cage one inside by the shocker bracket. Note OEM thee nut is one size and the bolt another! 5/8th and 11/16ths from memory. Access is tricky but is it doable.
  • remove the spring/shocker a a unit.
Thanks, Greg. At any point in the above process, do I need to be wary of releasing any stored energy in the spring? When I jack up the car, should I place the stands on jacking point on the sill forward of the wheel -- as opposed to putting the stands under the radius arms?
 
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Old 05-11-2020, 10:50 AM
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Originally Posted by Hedman
Thanks, Greg. At any point in the above process, do I need to be wary of releasing any stored energy in the spring? When I jack up the car, should I place the stands on jacking point on the sill forward of the wheel -- as opposed to putting the stands under the radius arms?
No stored spring energy on the rears. The shocks and springs are a unit (only separable once off the car) which are bolted to the car as a unit. Once the shocker is at its full extended travel that is that. The stand must be under the jacking point, so you cannot put the jack there. To jack the car either place the jack under the centre of the rear axle cage (piece of wood across the cage bottom plate) or under the large radius arm bush; then install the stand on the jacking point and relax the jack. You cannot leave the jack on the radius arm bush when removing the shocks as that prevents the suspension from fully dropping.
When you are driving out the pin, just ease the weight off the pin by supporting the hub a touch.
 
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Old 05-13-2020, 02:49 PM
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Originally Posted by Greg in France
No stored spring energy on the rears. The shocks and springs are a unit (only separable once off the car) which are bolted to the car as a unit. Once the shocker is at its full extended travel that is that. The stand must be under the jacking point, so you cannot put the jack there. To jack the car either place the jack under the centre of the rear axle cage (piece of wood across the cage bottom plate) or under the large radius arm bush; then install the stand on the jacking point and relax the jack. You cannot leave the jack on the radius arm bush when removing the shocks as that prevents the suspension from fully dropping.
When you are driving out the pin, just ease the weight off the pin by supporting the hub a touch.
Greg, I managed to get both spring & shock assemblies off of one side (more on that later). I purchased replacement Boges shocks and springs from Welsh. I had naively assumed they would arrive as an assembled coilover, but no such luck.

So how do I assemble them? I assume that I need a spring compression tool. How does the spring affix to the shock or vice versa?

The shocks came with a separate metal dish and 2 half moon metal pieces. I assume these are used to capture the spring after it is compressed, but how? Are they swedged in by the pressure of the spring, or do they need to be welded into place? Is there some trick that I am missing?
 
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Old 05-13-2020, 03:09 PM
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Originally Posted by Hedman
Greg, I managed to get both spring & shock assemblies off of one side (more on that later). I purchased replacement Boges shocks and springs from Welsh. I had naively assumed they would arrive as an assembled coilover, but no such luck.

So how do I assemble them? I assume that I need a spring compression tool. How does the spring affix to the shock or vice versa?

The shocks came with a separate metal dish and 2 half moon metal pieces. I assume these are used to capture the spring after it is compressed, but how? Are they swedged in by the pressure of the spring, or do they need to be welded into place? Is there some trick that I am missing?
Great choice of springs and shocks.
As you surmised, the springs have to be compressed. Then the spring is placed over the end of the shock so its other end is against the wide flanged end of the shock body. If you look carefully at the opposite end of the shock body, you will see a welded "ring" running round the body. The dished piece goes over this and the half-moon pieces go into the concave dished piece. When the spring compressors are released, the half moons jam together into the dish centre and their inner circumference locks against the welded ring. If your old spring/shocks are OEM, you will see that is how they are put together.
Typical compressor:
https://www.princessauto.com/en/deta...or/A-p2920186e
You need two compressors, one each side of the spring.
 
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  #26  
Old 05-13-2020, 03:19 PM
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Originally Posted by Greg in France

The dished piece goes over this and the half-moon pieces go into the concave dished piece. When the spring compressors are released, the half moons jam together into the dish centre and their inner circumference locks against the welded ring.
There is a boss or ridge on the inside of the half moon. I assume this is what engages with the ring on the shock piston. But this ridge is not centered within the half moon. Does the ridge go on top as in the left hand side of the photo, or towards the bottom as in the right hand side?



Which way should I orient the half moon pieces?
 
  #27  
Old 05-14-2020, 02:39 AM
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The LHS orientation in your photo is correct, and yes, that is the indent. My aftermarket shocks have the welded ring, sorry for the misinfo.
 
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Old 04-15-2021, 07:24 AM
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Default 88-89 accumulator replace bleed, ?

Originally Posted by JayJagJay
You'll find that. Yes.

In essence it's just about taking things apart being careful and certain everything goes back in the same order, in the same spot. I personally have NOT done this yet, want to and will. Folks here will help with the step by...

The trailing arms can be tougher to deal with for the home mechanic on some cars than others but it's also not so so bad. When you get there, start a thread.

Dude. Do make sure that you run all of that H2O out of the brake system. It's important
the pump is on motor not by key driven as 90-95 xj6 had. Mine VP 89 xj6 . The ball has a bleed hole on ball shaft . Would you not open valve hole then replace ball to tightness to allow air out at ball when replacing ball?
 
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Old 04-15-2021, 09:10 AM
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Originally Posted by Craig Geske
the pump is on motor not by key driven as 90-95 xj6 had. Mine VP 89 xj6 . The ball has a bleed hole on ball shaft . Would you not open valve hole then replace ball to tightness to allow air out at ball when replacing ball?
I'm not sure what you mean...
 
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Old 04-15-2021, 09:55 AM
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Originally Posted by JayJagJay
I'm not sure what you mean...
In 1988 and 1989 hydraulic pressure to feed the brake servo came from a secondary port on the power steering pump. In 1990 the brake system was changed and the pressure came from a dedicated electric pump.

One of the reasons was safety but the main reason was leaks and manufacturing simplicity. If the engine stalled and you got past your accumulated brake pressure you'd have greatly diminished braking ability. The electric pump would run in more failure scenarios. Having extra high pressure power steering hoses to feed the brake servo was oily and much harder to manufacture. Separating the engine from the brake system also eased manufacturing becasue brake system components are often installed early in the manufacturing process and engines are installed at a later stage.

This wasn't a jag only thing, it was across many brands. These type brake system is commonly called 'hydroboost' and in high end car like Jag and BMW's of the time the engine driven hydraulic pump operated the steering assist, brake assist and suspension leveling system. On many makes this oily system was nightmarish and often leaked and failed in many ways.
 

Last edited by icsamerica; 04-15-2021 at 10:05 AM.
  #31  
Old 04-16-2021, 06:09 AM
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Originally Posted by icsamerica
In 1988 and 1989 hydraulic pressure to feed the brake servo came from a secondary port on the power steering pump. In 1990 the brake system was changed and the pressure came from a dedicated electric pump.

One of the reasons was safety but the main reason was leaks and manufacturing simplicity. If the engine stalled and you got past your accumulated brake pressure you'd have greatly diminished braking ability. The electric pump would run in more failure scenarios. Having extra high pressure power steering hoses to feed the brake servo was oily and much harder to manufacture. Separating the engine from the brake system also eased manufacturing becasue brake system components are often installed early in the manufacturing process and engines are installed at a later stage.

This wasn't a jag only thing, it was across many brands. These type brake system is commonly called 'hydroboost' and in high end car like Jag and BMW's of the time the engine driven hydraulic pump operated the steering assist, brake assist and suspension leveling system. On many makes this oily system was nightmarish and often leaked and failed in many ways.
I see. Did not know that. Thank you...
 
  #32  
Old 04-16-2021, 06:44 AM
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[QUOTE=JayJagJay;2379593]I see. Did not know that. Thank you...[/QUOT

Just to be clear... This was on on the XJ6 not the XJS. The XJS had a vacuum servo until about 1987 and never had the hydroboost.
 
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