ZX Estate brake compensator unit

Plane Fixer · Post by **Plane Fixer** » 24 Apr 2004, 03:59

My ZX TD Estate (1996) just failed the MOT [:(] on a seized o/s/r brake compensator unit. Are these only fitted to the Estate as my "Haynes book of lies" [:D] doesn't even mention it. Now, I think I have freed it up with a good dose of lubricant, but as it seems to work on the rise and fall of the suspension arm how do I check it (other than by trying to jack up the wheel??). Just one other thing, what exactly does it do and why is it only on the Estate version??
Thanks for any help/advice...The car has been good so far and has done 115,000 (only had 55,000 when I bought it).

Dave Burns · Post by **Dave Burns** » 24 Apr 2004, 14:14

This type of compensator is only fitted to the estate (though a purely hydraulic version is used for rear disc brake setups), since estate's are often used as heavy load carrier's they require more agressive rear brakes than the hatchbacks when carrying loads, but during times when no load is being carried the rear brakes must have their power reduced to prevent very dangerous rear wheel lockup under severe braking conditions.
So the device is a very important part of the braking equipment, it has a moving piston inside it which cuts of increasing pressure at a pre-defined limit, the piston is connected to an arm on outside of the unit and as the piston moves so does the arm.
The arm moves against a spring load between it and the suspension arm damper mounting, as weight is put in the rear of the car it naturally presses the car down on its suspension, this also increases pressure on the compensator's spring, meaning that a higher fluid pressure is now required to move the compensators arm against the increased spring pressure, thus more pressure is made available to the rear brakes to compensate for the heavier load being carried.
If not allready done and before any dismanteling of the unit, take measurements of the adjusting rod and the springs position on it, the arm should move at relatively low pedal pressure when unloaded, (though if it moves at too low a pressure it will again fail the test) but require more pedal pressure to move it when the car is loaded.
Make sure there are no leaks, all to common when they have been rusted solid and freed off, new ones are about £65 from main dealers only.
Dave
Hehe, I'll get this right in a minute[:D]

alexx · Post by **alexx** » 26 Apr 2004, 14:47

Well, ordinary ZX 1.4 hatchback that I saw last time in the garage when I got my accu sphere regassed had this brake compensator unit, beside the right rear arm. I was surprised, because this unit isn't mentioned in Haynes.

Plane Fixer · Post by **Plane Fixer** » 27 Apr 2004, 05:20

Well the car got through the MOT today[:)] compensator freed up well and no leaks to be seen (although in light of Dave's reply, I will monitor it every week to check for leaks in the next few months). Thanks for the help.
96 ZX TD Estate 115,000...still going strong.

Dave Burns · Post by **Dave Burns** » 27 Apr 2004, 05:46

Why would a lowly 1.4 hatchback have one of these fitted, I can't imagine it being there as standard, it would not be required unless it had estate rear brakes with the larger drums.
I've been under a few zx hatch's and never come accross it, seen loads in breakers yards and still no sign of it, only ever on estates in the UK and on all that I've seen so far.
Dave